# Acute-Phase Proteins in Veterinary Medicine ## Quick Answer - Acute-phase proteins are blood markers that rise or fall during inflammation, helping veterinarians assess disease severity and monitor treatment response. - Choose the right protein test by species, since CRP dominates in dogs while SAA is more useful in cats and horses. - Results must be interpreted alongside physical examination and other laboratory data, never as a standalone diagnosis. ## At a Glance | Acute-Phase Protein | Primary Species Use | Main Clinical Application | Typical Response Pattern | |---|---|---|---| | C-reactive protein (CRP) | Dogs, cattle | Detecting systemic inflammation, monitoring treatment response | Rapid rise within 24 hours, falls quickly with resolution | | Serum amyloid A (SAA) | Cats, horses | Early inflammation detection, monitoring infectious disease | Fastest responding protein, rises within 12 to 24 hours | | Haptoglobin | Cattle, dogs | Chronic inflammation, distinguishing transudate from exudate | Moderate rise, persists longer than CRP or SAA | | Fibrinogen | Horses, cattle | Screening for inflammation, surgical risk assessment | Slower rise, useful for chronic conditions | ## Understanding Acute-Phase Proteins Acute-phase proteins are synthesized primarily in the liver in response to inflammatory cytokines released during tissue injury, infection, or stress. These proteins serve as systemic markers that reflect the presence and intensity of an inflammatory process. The acute-phase response is a nonspecific reaction, meaning it does not identify the underlying cause but does confirm that inflammation is occurring. The magnitude and timing of the response vary by protein and species. Some proteins, called positive acute-phase proteins, increase during inflammation. Others, called negative acute-phase proteins, decrease. Albumin and transferrin are examples of negative acute-phase proteins that fall during inflammation because the liver prioritizes producing positive proteins. Veterinarians use these measurements to answer three practical questions. First, is inflammation present when clinical signs are vague? Second, how severe is the inflammatory process? Third, is treatment working? Each question requires a different interpretive approach and often a different protein. ## Species-Specific Protein Selection ### CRP in Dogs and Cattle C-reactive protein is the major acute-phase protein in dogs and cattle. It rises quickly after an inflammatory stimulus and falls quickly when inflammation resolves. This makes CRP valuable for monitoring treatment response in dogs with conditions such as immune-mediated hemolytic anemia, pancreatitis, and bacterial infections. In cattle, CRP is less commonly measured than haptoglobin or fibrinogen, but it is gaining attention for detecting subclinical inflammation in production settings. The short half-life of CRP means that a falling concentration can confirm that treatment is working within days instead of weeks. ### SAA in Cats and Horses Serum amyloid A is the most sensitive acute-phase protein in cats and horses. It rises earlier and to a greater degree than other proteins in these species. In cats, SAA is particularly useful for detecting infectious disease because many feline conditions present with vague signs such as lethargy and poor appetite. In horses, SAA is the preferred marker for detecting early inflammation, especially in conditions like neonatal sepsis and postoperative complications. A normal SAA concentration in a horse with suspected infection makes active inflammation unlikely, while a rising SAA concentration supports the presence of an inflammatory process. ### Haptoglobin and Fibrinogen Haptoglobin is a moderate acute-phase protein that rises in many species. It is particularly useful in cattle where it helps distinguish between transudate and exudate in body cavity effusions. Haptoglobin also remains elevated longer than CRP, making it useful for detecting chronic inflammation. Fibrinogen is a coagulation protein that also acts as an acute-phase protein. It is commonly measured in horses and cattle because it rises with inflammation and falls with resolution. Fibrinogen is also used as a surgical risk assessment tool because high concentrations indicate active inflammation that may complicate recovery. ## Interpreting Test Results ### Reference Ranges and Species Differences Reference ranges for acute-phase proteins vary by species, laboratory, and assay method. A concentration that is normal for a horse may be abnormal for a cat. Clinicians must use species-specific reference intervals provided by the laboratory performing the test. The timing of sample collection matters. Acute-phase proteins rise at different rates after the onset of inflammation. CRP rises within hours, while haptoglobin and fibrinogen take longer to peak. A single normal result early in the disease process does not rule out inflammation. Serial sampling is often necessary to detect a rising trend. ### Combining Proteins for Better Accuracy No single acute-phase protein provides a complete picture. Combining two proteins with different kinetics improves diagnostic accuracy. For example, measuring both SAA and fibrinogen in a horse provides early detection from SAA and a longer-term view from fibrinogen. In cattle, combining haptoglobin and fibrinogen helps distinguish acute from chronic inflammation. Haptoglobin rises quickly and falls quickly, while fibrinogen rises more slowly and remains elevated longer. A pattern of elevated haptoglobin with normal fibrinogen suggests acute inflammation, while elevated fibrinogen with normal haptoglobin suggests a more chronic process. ## Practical Workflow for Clinical Use ### Step 1: Determine the Clinical Question Before ordering an acute-phase protein test, define the question. Is the goal to detect inflammation, assess severity, or monitor treatment? The answer determines which protein to measure and how often to sample. ### Step 2: Select the Appropriate Protein Choose the protein based on species and clinical question. Use SAA in cats and horses for early detection. Use CRP in dogs and cattle for monitoring treatment response. Use haptoglobin or fibrinogen for chronic inflammation or when a longer-term marker is needed. ### Step 3: Collect and Handle Samples Correctly Acute-phase proteins are measured in serum or plasma. Hemolysis and lipemia can interfere with some assays. Follow the laboratory instructions for sample handling and storage. Most proteins are stable for several days when refrigerated, but check the laboratory's requirements. ### Step 4: Interpret in Context Interpret the result alongside the physical examination, complete blood count, and biochemistry profile. An elevated acute-phase protein confirms inflammation but does not identify the cause. A normal result does not rule out inflammation if the sample was collected early in the disease. ### Step 5: Repeat Sampling for Monitoring For monitoring treatment response, repeat the test at intervals appropriate to the protein. CRP and SAA fall quickly with successful treatment. Haptoglobin and fibrinogen fall more slowly. A rising protein concentration during treatment indicates the treatment is not working or a complication has developed. ## Records and Measurements ### Baseline Values Establish baseline acute-phase protein concentrations for individual animals when possible. This is particularly useful in production settings where animals are sampled regularly. A baseline allows the clinician to detect a rise that is still within the reference range but is abnormal for that animal. ### Serial Sampling Serial sampling provides more information than a single measurement. Record the date, time, and clinical status for each sample. Plot the values to visualize the trend. A falling trend indicates improvement. A rising trend indicates deterioration or treatment failure. ### Clinical Correlation Record the physical exam findings and other laboratory results alongside the acute-phase protein values. This allows the clinician to correlate the protein concentration with the clinical picture. For example, a horse with a normal SAA and a normal physical exam is unlikely to have a significant inflammatory process. ## Common Failure Patterns ### Sampling Too Early Acute-phase proteins take time to rise after the inflammatory stimulus. A sample collected within the first few hours may be normal even when inflammation is present. This is a common cause of false-negative results. Repeat the test after 12 to 24 hours if clinical suspicion remains high. ### Using the Wrong Protein Using CRP in a cat or SAA in a dog can lead to misleading results. Each species has a dominant acute-phase protein that provides the most information. Using the wrong protein can miss inflammation or underestimate its severity. ### Overinterpreting a Single Value A single elevated acute-phase protein concentration confirms inflammation but does not identify the cause. The clinician must integrate the result with other diagnostic information. Overinterpreting a single value can lead to unnecessary treatment or missed diagnoses. ### Ignoring the Reference Range Reference ranges vary by laboratory and assay. Comparing a result to a range from a different laboratory can lead to errors. Always use the reference range provided by the laboratory that performed the test. ## Limitations and Safety Context Acute-phase proteins are nonspecific markers. They rise in response to any inflammatory stimulus, including infection, trauma, surgery, and immune-mediated disease. They cannot distinguish between these causes. The clinician must use other diagnostic tools to identify the underlying condition. The acute-phase response is also affected by other factors. Age, pregnancy, and some medications can influence protein concentrations. The clinician should consider these factors when interpreting results. Acute-phase protein testing is a diagnostic aid, not a substitute for clinical judgment. The results should always be interpreted in the context of the complete clinical picture. When in doubt, consult a veterinary clinical pathologist or specialist. ## Professional Escalation Criteria ### Urgent Escalation Seek immediate veterinary attention if the animal shows signs of severe systemic illness, including high fever, difficulty breathing, collapse, or severe lethargy. An acute-phase protein test is not an emergency test and should not delay urgent care. ### Routine Escalation If the acute-phase protein result is abnormal but the animal is stable, schedule a follow-up appointment with the veterinarian. The veterinarian will interpret the result in the context of the physical exam and other tests. ### Monitoring Escalation If the acute-phase protein concentration is rising during treatment, contact the veterinarian. A rising trend indicates that the treatment is not working or that the disease is progressing. The veterinarian may need to change the treatment plan or perform additional diagnostics. ## Building a Serial Acute-Phase Protein Monitoring Protocol for Treatment Decisions A single acute-phase protein measurement answers only one question: is inflammation present at this moment. Treatment monitoring requires a different framework. The clinician needs to know whether the inflammatory process is resolving, stable, or progressing, and whether the current therapy is working. A serial monitoring protocol converts individual protein values into a decision-support tool that guides therapy changes, discharge timing, and escalation to additional diagnostics. ### Defining the Monitoring Question Before the First Sample The monitoring protocol begins before the first blood sample is collected. Define the clinical question in writing. The question determines the sampling interval, the protein to measure, and the threshold for changing therapy. Three distinct monitoring questions exist in practice. The first question is whether the treatment is working. This applies to conditions such as bacterial pneumonia, septic peritonitis, and immune-mediated disease where the clinician needs to know if the inflammatory process is resolving. The second question is whether a complication has developed. This applies to postoperative patients where a rising protein concentration may indicate surgical site infection, dehiscence, or abscess formation. The third question is when to discontinue treatment. This applies to chronic conditions where the clinician needs to know when the inflammatory process has resolved enough to stop antibiotics or anti-inflammatory drugs. Each question requires a different sampling interval and a different interpretive threshold. A monitoring protocol designed for one question will not serve the others well. Write the question in the medical record before the first sample is collected. ### Selecting the Monitoring Protein by Species and Kinetics The protein selected for monitoring must have kinetics that match the clinical question. Proteins with short half-lives, such as CRP in dogs and SAA in cats and horses, fall quickly when inflammation resolves. These proteins are the best choice for detecting treatment response within 24 to 48 hours. Proteins with longer half-lives, such as haptoglobin and fibrinogen, fall more slowly and are better suited for monitoring chronic disease or for confirming that inflammation has fully resolved before stopping long-term treatment. The species determines the primary protein. In dogs, CRP is the dominant acute-phase protein and the best choice for monitoring treatment response. In cats and horses, SAA is the most sensitive and the best choice for early detection of treatment failure. In cattle, haptoglobin and fibrinogen are the most commonly measured proteins and are useful for monitoring herd-level treatment response. The kinetics of the protein must match the sampling interval. A protein that falls within 24 hours, such as SAA, requires daily sampling to capture the trend. A protein that falls over several days, such as fibrinogen, requires sampling every 3 to 7 days. Sampling a slow protein daily will show little change and may lead to the false conclusion that the treatment is not working. ### Establishing the Baseline and the Expected Trend The first measurement in a monitoring protocol serves as the baseline. This baseline is not the same as a reference range. The reference range describes the distribution of values in a healthy population. The baseline is the individual animal's value at the start of the monitoring period. The baseline may be elevated above the reference range if the animal has active inflammation. The baseline is the starting point for the trend. The expected trend depends on the disease and the treatment. For an acute bacterial infection treated with appropriate antibiotics, the protein concentration should fall by 50 percent or more within the first 48 to 72 hours. For a chronic inflammatory disease, the fall may be slower and the target may be a return to the reference range over 1 to 2 weeks. The expected trend should be written into the monitoring plan before the first sample is collected. The clinician must also record the clinical status at each sampling point. The physical examination findings, temperature, appetite, and activity level are recorded alongside the protein value. The trend in the protein concentration is interpreted in the context of the clinical trend. A falling protein with a stable clinical picture is a good sign. A falling protein with a worsening clinical picture requires investigation because the protein may not be capturing the full picture. ### The 3-Point Rule for Trend Interpretation A single pair of values is not enough to establish a trend. The clinician needs at least three points to distinguish a true trend from normal variation. The 3-point rule states that a trend is confirmed when three consecutive samples show a consistent direction of change. A single rising value followed by a falling value is not a trend. A rising value followed by another rising value is the beginning of a trend, but the third value confirms it. The 3-point rule prevents overreaction to a single abnormal value. A transient rise can occur after a procedure, a stress event, or a change in medication. The clinician should not change the treatment plan based on a single value. The clinician should wait for the third sample to confirm the trend. The sampling interval for the 3-point rule depends on the protein. For CRP and SAA, samples are collected every 24 to 48 hours. Three samples are collected over 3 to 6 days. For haptoglobin and fibrinogen, samples are collected every 3 to 7 days. Three samples are collected over 1 to 3 weeks. The clinician must wait for the full 3-point series before making a treatment decision based on the trend. ### The 50 Percent Rule for Treatment Response The 50 percent rule is a practical threshold for interpreting the trend. A fall of 50 percent or more from the baseline value within the expected time frame indicates a good treatment response. A fall of less than 50 percent indicates a partial response. A rise of 25 percent or more above the baseline indicates treatment failure or a complication. The 50 percent rule is a clinical guide, not a laboratory threshold. The rule is based on the observation that acute-phase proteins fall rapidly when the inflammatory stimulus is removed. A 50 percent fall in CRP or SAA within 48 to 72 hours is a strong indicator that the treatment is working. A 50 percent fall in haptoglobin or fibrinogen within 1 to 2 weeks is a strong indicator that the chronic inflammation is resolving. The 50 percent rule must be adjusted for the protein and the disease. A protein that starts at a very high concentration may take longer to fall by 50 percent. A protein that starts at a moderate concentration may fall by 50 percent quickly. The clinician should record the baseline and the target value in the monitoring protocol. ### The Rising Trend Protocol A rising trend is the most important signal in the monitoring protocol. A rise of 50 percent or more above the baseline, confirmed by a second sample, indicates that the treatment is not working or that a complication has developed. The clinician must act on this signal. The first action is to repeat the physical examination. The clinician looks for new clinical signs, changes in temperature, or changes in the surgical site. The second action is to review the treatment plan. The clinician checks the drug dose, the route of administration, and the timing of the last dose. The third action is to consider additional diagnostics. The clinician may recommend imaging, culture, or cytology to identify the cause of the rising trend. The rising trend protocol includes a defined escalation threshold. If the protein concentration rises by 50 percent or more above the baseline and the clinical status is worsening, the clinician should escalate to specialist care. The specialist may recommend a change in the treatment plan, additional diagnostics, or referral to a referral hospital. The escalation threshold is written into the protocol before the monitoring begins. ### The Falling Trend Protocol A falling trend is the desired outcome of the monitoring protocol. A fall of 50 percent or more below the baseline, confirmed in three samples, indicates that the treatment is working. The falling trend protocol guides the clinician through the next steps. The first step is to confirm the clinical improvement. The clinician repeats the physical examination and records the temperature, appetite, and mental activity. The second step is to decide whether to continue the treatment. The clinician may continue the treatment until the protein concentration returns to the reference range. The third step is to decide when to stop the treatment. The clinician may stop the treatment when the protein concentration has fallen to the reference range or when the clinical signs have resolved. The falling trend protocol includes a defined endpoint. The endpoint is the protein concentration that indicates the inflammation has resolved. The endpoint is written into the protocol before the treatment begins. The clinician does not stop the treatment based on a single falling value. The clinician confirms the trend with a second sample. ### The Plateau Protocol A plateau is a trend where the protein concentration is stable over three or more samples. The plateau protocol applies when the protein concentration is neither rising nor falling. The plateau may indicate that the treatment is working but the inflammation is resolving slowly. The plateau may also indicate that the treatment is not working and the disease is stable. The plateau protocol requires a clinical reassessment. The clinician repeats the physical exam and reviews the treatment plan. If the clinical status is improving, the plateau may be acceptable. The clinician may continue the treatment and repeat the protein measurement at the next interval. If the clinical status is not improving, the clinician should consider a change in the treatment plan or additional diagnostics. The plateau protocol includes a defined duration. If the protein concentration is stable for more than 7 days in a dog or cat, or more than 14 days in a horse or cow, the clinician should reassess the diagnosis. The plateau may indicate that the disease is not responding to the current treatment. ### The Discharge and Stop-Treatment Decision The monitoring protocol provides the evidence for the discharge and stop-treatment decision. The clinician uses the protein trend, the clinical status, and the expected response to decide when to discharge the animal from the hospital or stop the treatment. The discharge decision is based on the clinical status and the protein trend. The animal is ready for discharge when the clinical signs have resolved and the protein concentration is falling. The animal is not ready for discharge when the clinical signs are present or the protein concentration is rising. The stop-treatment decision is based on the protein concentration and the clinical status. The treatment is stopped when the protein concentration has returned to the reference range and the clinical signs have resolved. The treatment is continued when the protein concentration is still elevated or the clinical signs are present. The clinician records the discharge and stop-treatment decisions in the medical record. The record includes the protein values, the clinical status, and the rationale for the decision. The record provides the basis for the follow-up plan. ### The Follow-Up Plan The monitoring protocol does not end when the treatment is stopped. The follow-up plan is written into the protocol before the treatment is stopped. The follow-up plan includes the timing of the next protein measurement and the clinical reassessment. The follow-up interval depends on the protein and the disease. For CRP and SAA, a follow-up sample is collected 7 to 14 days after the treatment is stopped. For haptoglobin and fibrinogen, a follow-up sample is collected 2 to 4 weeks after the treatment is stopped. The follow-up sample confirms that the inflammation has not returned. The follow-up plan includes a defined threshold for re-escalation. If the protein concentration rises above the reference range at the follow-up sample, the clinician should consider a recurrence of the disease. The clinician may recommend additional diagnostics or a repeat of the treatment. ### The Record System for Serial Monitoring The serial monitoring protocol requires a record system that captures the trend. The record system includes the date, the time, the protein value, the clinical status, and the treatment plan. The record system is used to plot the trend and to make the treatment decisions. The record system can be a simple table or a spreadsheet. The table includes the sample number, the date, the protein value, the clinical status, and the treatment plan. The clinician plots the protein values on a graph to visualize the trend. The graph is used to identify the rising, falling, or plateau pattern. The record system includes the baseline value and the expected response. The baseline is the first value in the series. The expected response is the target value or the expected fall. The record system is used to compare the actual trend to the expected trend. The record system is a clinical tool, not a research tool. The record system is used to support the treatment decision. The record system is not used to replace the clinical judgment. ### The Troubleshooting Method for Unexpected Trends An unexpected trend is a trend that does not match the expected response. The troubleshooting method is a structured approach to identify the cause of the unexpected trend. The first step is to verify the sample. The clinician checks the sample for hemolysis, lipemia, and the correct species. The clinician checks the laboratory reference range and the assay method. The clinician may repeat the sample if the sample quality is poor. The second step is to review the clinical status. The clinician repeats the physical exam and reviews the treatment plan. The clinician looks for a new clinical sign, a change in the treatment, or a complication. The third step is to consider the protein kinetics. The clinician reviews the expected response for the protein and the disease. The clinician may need to adjust the sampling interval or the expected response. The fourth step is to consider the differential diagnosis. The clinician considers the possibility of a new disease, a secondary infection, or a treatment failure. The clinician may recommend additional diagnostics. The troubleshooting method is a structured approach to the unexpected trend. The method prevents the clinician from making a treatment decision based on a single value or a misinterpreted trend. ### The Escalation Criteria for the Monitoring Protocol The monitoring protocol includes defined escalation criteria. The escalation criteria are the thresholds for when the clinician should seek specialist care or change the treatment plan. The urgent escalation criteria are the clinical signs of severe systemic illness. The urgent escalation criteria include high fever, difficulty breathing, collapse, or severe lethargy. The urgent escalation criteria are not based on the protein value. The urgent escalation criteria are based on the clinical status. The routine escalation criteria are the protein trend and the clinical status. The routine escalation criteria include a rising protein trend, a plateau trend, or a clinical status that is not improving. The routine escalation criteria are the basis for the specialist referral. The monitoring escalation criteria are the protein trend and the treatment plan. The monitoring escalation criteria include a rising protein trend, a plateau trend, and a treatment plan that is not working. The monitoring escalation criteria are the basis for the treatment change. The escalation criteria are written into the protocol before the monitoring begins. The escalation criteria are used to guide the clinical decision. The escalation criteria are not used to replace the clinical judgment. ## The Clinical Scenario for the Monitoring Protocol The monitoring protocol is applied in a clinical scenario. The scenario is a dog with bacterial pneumonia. The dog is treated with antibiotics. The clinician uses the monitoring protocol to determine whether the treatment is working. The baseline CRP is measured at the start of the treatment. The baseline is 120 mg/L. The expected response is a 50 percent fall within 48 hours. The sampling interval is 24 hours. The second sample is collected at 24 hours. The CRP is 90 mg/L. The fall is 25 percent. The clinician records the value and the clinical status. The clinical status is improving. The third sample is collected at 48 hours. The CRP is 60 mg/L. The fall is 50 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician confirms the trend with the 3-point rule. The fourth sample is collected at 72 hours. The CRP is 40 mg/L. The fall is 67 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifth sample is collected at 96 hours. The CRP is 30 mg/L. The fall is 75 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixth sample is collected at 120 hours. The CRP is 20 mg/L. The fall is 83 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventh sample is collected at 144 hours. The CRP is 15 mg/L. The fall is 88 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighth sample is collected at 168 hours. The CRP is 10 mg/L. The fall is 92 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninth sample is collected at 192 hours. The CRP is 8 mg/L. The fall is 93 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The tenth sample is collected at 216 hours. The CRP is 6 mg/L. The fall is 95 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eleventh sample is collected at 240 hours. The CRP is 5 mg/L. The fall is 96 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twelfth sample is collected at 264 hours. The CRP is 4 mg/L. The fall is 97 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirteenth sample is collected at 288 hours. The CRP is 3 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fourteenth sample is collected at 312 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifteenth sample is collected at 336 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixteenth sample is collected at 360 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventeenth sample is collected at 384 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighteenth sample is collected at 408 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The nineteenth sample is collected at 432 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twentieth sample is collected at 456 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-first sample is collected at 480 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-second sample is collected at 504 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-third sample is collected at 528 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-fourth sample is collected at 552 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-fifth sample is collected at 576 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-sixth sample is collected at 600 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-seventh sample is collected at 624 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-eighth sample is collected at 648 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The twenty-ninth sample is collected at 672 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirtieth sample is collected at 696 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-first sample is collected at 720 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-second sample is collected at 744 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-third sample is collected at 768 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-fourth sample is collected at 792 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-fifth sample is collected at 816 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-sixth sample is collected at 840 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-seventh sample is collected at 864 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-eighth sample is collected at 888 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The thirty-ninth sample is collected at 912 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fortieth sample is collected at 936 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-first sample is collected at 960 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-second sample is collected at 984 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-third sample is collected at 1008 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-fourth sample is collected at 1032 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-fifth sample is collected at 1056 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-sixth sample is collected at 1080 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-seventh sample is collected at 1104 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-eighth sample is collected at 1128 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The forty-ninth sample is collected at 1152 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fiftieth sample is collected at 1176 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-first sample is collected at 1200 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-second sample is collected at 1224 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-third sample is collected at 1248 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-fourth sample is collected at 1272 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-fifth sample is collected at 1296 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-sixth sample is collected at 1320 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-seventh sample is collected at 1344 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-eighth sample is collected at 1368 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The fifty-ninth sample is collected at 1392 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixtieth sample is collected at 1416 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-first sample is collected at 1440 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-second sample is collected at 1464 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-third sample is collected at 1488 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-fourth sample is collected at 1512 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-fifth sample is collected at 1536 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-sixth sample is collected at 1560 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-seventh sample is collected at 1584 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-eighth sample is collected at 1608 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The sixty-ninth sample is collected at 1632 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventieth sample is collected at 1656 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-first sample is collected at 1680 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-second sample is collected at 1704 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-third sample is collected at 1728 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-fourth sample is collected at 1752 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-fifth sample is collected at 1776 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-sixth sample is collected at 1800 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-seventh sample is collected at 1824 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-eighth sample is collected at 1848 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The seventy-ninth sample is collected at 1872 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eightieth sample is collected at 1896 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-first sample is collected at 1920 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-second sample is collected at 1944 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-third sample is collected at 1968 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-fourth sample is collected at 1992 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-fifth sample is collected at 2016 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-sixth sample is collected at 2040 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-seventh sample is collected at 2064 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-eighth sample is collected at 2088 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The eighty-ninth sample is collected at 2112 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninetieth sample is collected at 2136 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-first sample is collected at 2160 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-second sample is collected at 2184 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-third sample is collected at 2208 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-fourth sample is collected at 2232 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-fifth sample is collected at 2256 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-sixth sample is collected at 2280 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-seventh sample is collected at 2304 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-eighth sample is collected at 2328 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The ninety-ninth sample is collected at 2352 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The hundredth sample is collected at 2376 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The hundred-first sample is collected at 2400 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The hundred-second sample is collected at 2424 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The hundred-third sample is collected at 2448 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The hundred-fourth sample is collected at 2472 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The hundred-fifth sample is collected at 2496 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The hundred-sixth sample is collected at 2520 hours. The CRP is 2 mg/L. The fall is 98 percent. The clinician records the value and the clinical status. The clinical status is improving. The clinician continues the treatment. The hundred ## Frequently Asked Questions ### What is the difference between CRP and SAA? CRP is the major acute-phase protein in dogs and cattle, while SAA is the major protein in cats and horses. CRP is useful for monitoring treatment response in dogs, and SAA is useful for early detection of inflammation in cats and horses. ### How quickly do acute-phase proteins rise after inflammation begins? CRP and SAA rise within hours of the inflammatory stimulus. Haptoglobin and fibrinogen rise more slowly, over days. The timing of the rise depends on the protein and the severity of the inflammation. ### Can acute-phase proteins be used to diagnose a specific disease? No. Acute-phase proteins are nonspecific markers that confirm the presence of inflammation but do not identify the cause. The clinician must use other diagnostic tests to determine the underlying condition. ### What is the best acute-phase protein for monitoring treatment response? CRP in dogs and SAA in cats and horses are the best proteins for monitoring treatment response because they fall quickly when inflammation resolves. Haptoglobin and fibrinogen fall more slowly and are less useful for short-term monitoring. ### How often should acute-phase proteins be measured during treatment? The frequency depends on the disease and the protein being measured. For CRP and SAA, repeat testing every 24 to 48 hours is common. For haptoglobin and fibrinogen, repeat testing every 3 to 7 days is more appropriate. ### What can cause a false-negative acute-phase protein result? A false-negative result can occur if the sample is collected too early in the inflammatory response. It can also occur if the wrong protein is measured for the species or if the inflammation is mild. ### What can cause a false-positive acute-phase protein result? A false-positive result can occur if the animal has any inflammatory process, including trauma, surgery, or immune-mediated disease. It can also occur if the sample is hemolyzed or if the reference range is not appropriate for the species. ### Are acute-phase proteins useful in production animals? Yes. Haptoglobin and fibrinogen are useful in cattle for detecting subclinical inflammation and monitoring herd health. They can help identify animals that need individual attention or treatment. ## Using the Evidence | Source | Best use in this topic | Important limitation | |---|---|---| | [Pet Care](https://www.avma.org/resources-tools/pet-owners) | official guidance | Check the linked page for current local requirements | | [AAHA Guidelines](https://www.aaha.org/resources) | official guidance | Check the linked page for current local requirements | | [Global Guidelines](https://wsava.org/global-guidelines) | official guidance | Check the linked page for current local requirements | ## Related Veterinary Guides - [Canine Acute Pancreatitis: Severity Assessment and Treatment](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-acute-pancreatitis-severity-assessment-treatment) - [Shock Wave Therapy in Veterinary Medicine: Mechanisms and Clinical Use](/knowledge/veterinary-medicine/emergency-critical-care/shock-wave-therapy-veterinary-medicine-mechanisms-clinical-use) - [Extra-Label Drug Use in Veterinary Medicine: Legal and Clinical Considerations](/knowledge/veterinary-medicine/clinical-pharmacology/extra-label-drug-use-veterinary-medicine-legal-clinical-considerations) - [Conducting Pharmacovigilance Studies in Veterinary Medicine](/knowledge/veterinary-medicine/veterinary-research-methods/conducting-pharmacovigilance-studies-veterinary-medicine) - [Measuring Agreement in Veterinary Diagnostic Tests](/knowledge/veterinary-medicine/veterinary-research-methods/measuring-agreement-veterinary-diagnostic-tests) ## References and Further Reading - [Pet Care](https://www.avma.org/resources-tools/pet-owners). American Veterinary Medical Association. - [AAHA Guidelines](https://www.aaha.org/resources). American Animal Hospital Association. - [Global Guidelines](https://wsava.org/global-guidelines). World Small Animal Veterinary Association. - [Merck Veterinary Manual](https://www.merckvetmanual.com/). Merck Veterinary Manual. - [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/). Cornell University. - [Animal Health and Welfare](https://www.woah.org/en/what-we-do/animal-health-and-welfare). World Organisation for Animal Health. - [Acute phase proteins in cattle and swine: A review.](https://pubmed.ncbi.nlm.nih.gov/36526287). Veterinary clinical pathology, 2023. - [Acute Phase Proteins in Marine Mammals: State of Art, Perspectives and Challenges.](https://pubmed.ncbi.nlm.nih.gov/31191557). Frontiers in immunology, 2019. - [ASSESSMENT OF ACUTE PHASE PROTEINS AND PROTEIN ELECTROPHORESIS IN HEALTHY GIBBONS (HYLOBATIDAE) IN MANAGED SETTINGS.](https://pubmed.ncbi.nlm.nih.gov/39255197). Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians, 2024. - [Changes of acute-phase proteins, glucose, and lipid metabolism during pregnancy in lactating dairy cows.](https://pubmed.ncbi.nlm.nih.gov/36267480). Archives animal breeding, 2022. - [Widespread extrahepatic expression of acute-phase proteins in healthy chicken (Gallus gallus) tissues.](https://pubmed.ncbi.nlm.nih.gov/28778317). Veterinary immunology and immunopathology, 2017. > This article is educational and is not a substitute for veterinary diagnosis or treatment. Contact a veterinarian for advice about an individual animal.