# Urinalysis Artifacts and Pitfalls ## Quick Answer - Urinalysis artifacts from improper collection, delayed testing, or reagent strip mishandling can mimic kidney disease, urinary tract infection, or metabolic disorders in veterinary patients. - Collect fresh urine in clean containers, analyze within 30 to 60 minutes, and refrigerate if delay is unavoidable to minimize cellular degradation and bacterial overgrowth. - No single artifact pattern is pathognomonic, so confirm abnormal findings with sediment microscopy and repeat sampling before making clinical decisions. ## At a Glance | Artifact Category | Common Cause | Typical False Result | Prevention Strategy | |---|---|---|---| | Cellular degradation | Delayed analysis, dilute urine | False negative sediment findings, casts dissolve | Analyze within 30 minutes or refrigerate and analyze within 6 hours | | Bacterial overgrowth | Room temperature storage | False positive nitrite, pH shift, turbidity | Refrigerate promptly, use preservative tubes when available | | Reagent strip contamination | Improper storage, expired strips, touching pads | False positive protein, glucose, blood | Store strips in sealed container, check expiry, handle by edges | | Chemical interference | Vitamin C, antibiotics, contrast media | False negative glucose, blood | Note patient medications, use confirmatory tests | | Physical contamination | Feces, litter, genital discharge | False positive protein, blood, bacteria | Use cystocentesis or clean midstream collection | | Temperature effects | Cold urine, refrigerated sample | Crystalluria, pH changes | Warm to room temperature before analysis | ## Understanding Urinalysis Artifacts in Veterinary Practice Urinalysis is a foundational diagnostic tool in veterinary medicine, providing rapid information about renal function, metabolic status, and urinary tract health. The American Veterinary Medical Association emphasizes the importance of routine preventive care and diagnostic testing for companion animals, and urinalysis is a core component of wellness examinations [1]. However, the diagnostic value of this test depends entirely on the quality of the sample and the accuracy of the analytical process. Artifacts, which are false or misleading results caused by preanalytical, analytical, or postanalytical errors, can lead to misdiagnosis, unnecessary treatment, or missed disease. The Merck Veterinary Manual provides authoritative background on the clinical application of urinalysis in veterinary medicine [4]. Understanding the sources of artifacts is essential for veterinary professionals, biology students, researchers, and laboratory personnel who interpret these results. This article catalogs common urinalysis artifacts, explains their mechanisms, and provides practical strategies for prevention and recognition. ## Preanalytical Artifacts Preanalytical artifacts occur before the sample reaches the analyzer. These errors arise from collection methods, container selection, transport conditions, and storage duration. They are the most common source of urinalysis inaccuracies and are entirely preventable with proper technique. ### Collection Method and Contamination The method of urine collection significantly influences the presence of artifacts. Free catch, catheterization, and cystocentesis each have distinct contamination risks. Free catch samples are prone to contamination from the distal urethra, genital tract, and perineal skin. Catheterization can introduce bacteria from the urethra or bladder wall. Cystocentesis, while invasive, provides the most sterile sample and is the preferred method for urine culture. Contamination from the external environment can produce false positive results for protein, blood, and bacteria. For example, a free catch sample from a female dog with vaginal discharge may show protein and blood that are not from the urinary tract. Similarly, a sample collected from a litter box may contain litter particles that interfere with reagent strip readings. The American Animal Hospital Association provides guidance on preventive care protocols for companion animals, including diagnostic testing recommendations [2]. When collecting urine, the clinician should select the method based on the clinical question. For routine screening, a free catch sample may be adequate. For suspected urinary tract infection, cystocentesis is preferred to avoid contamination. ### Container Selection and Handling The urine container itself can introduce artifacts. Containers with detergent residue can cause false positive protein readings. Containers that are not sterile can introduce bacteria. Containers with certain plastics may absorb protein or glucose, leading to false negative results. The ideal urine container is sterile, leak-proof, and made of an inert material that does not interact with urine components. The container should be filled to an adequate volume, typically 5 to 10 mL, to allow for all tests. The container should be labeled with the patient identification, date, and time of collection. ### Timing and Storage Duration Urine is a dynamic biological fluid that changes rapidly after collection. The most significant changes occur within the first hour at room temperature. Cellular elements, including red blood cells, white blood cells, and casts, begin to lyse and degrade. Bacteria multiply, consuming glucose and altering pH. Urea is converted to ammonia by bacterial urease, increasing pH and causing crystals to form or dissolve. The Merck Veterinary Manual emphasizes the importance of timely analysis for accurate results [4]. For optimal accuracy, urine should be analyzed within 30 minutes of collection. If analysis is delayed, the sample should be refrigerated at 2 to 8 degrees Celsius. Refrigeration slows bacterial growth and cellular degradation but does not stop it entirely. Refrigerated samples should be analyzed within 6 hours and allowed to return to room temperature before analysis. ### Refrigeration and Its Effects Refrigeration preserves urine for a limited time but introduces its own artifacts. Cold temperatures can cause the precipitation of amorphous urates, phosphates, and other crystals. These crystals can interfere with the microscopic examination and may be misinterpreted as pathological crystalluria. When a refrigerated sample is analyzed, the sample must be thoroughly mixed and allowed to warm to room temperature. Warming the sample dissolves some crystals that formed during refrigeration, but not all. The clinician should note that the sample was refrigerated and interpret crystal findings with caution. ### Preservatives and Additives Commercial urine preservative tubes are available for veterinary use. These tubes contain a preservative that stabilizes urine components for up to 24 to 48 hours. The preservative prevents bacterial growth and cellular degradation. However, the preservative can interfere with some reagent strip tests, particularly the specific gravity measurement. The choice between a plain container and a preservative tube depends on the tests requested. If a complete urinalysis, including specific gravity, is needed, a plain container with prompt analysis is preferred. If only a culture is needed, a preservative tube may be acceptable. ## Analytical Artifacts Analytical artifacts occur during the actual testing process. These errors can be from reagent strip mishandling, improper technique, or instrument malfunction. They are often subtle and can be difficult to detect without proper quality control. ### Reagent Strip Storage and Handling Reagent strips are sensitive to moisture, light, and temperature. Strips that are stored improperly can degrade, producing false results. The strip container should be kept tightly closed when not in use. The desiccant packet should remain in the container. Strips should be stored at room temperature, away from direct sunlight and heat. The reagent pads on the strip should not be touched with fingers. Oils and moisture from the skin can contaminate the pads and affect the chemical reactions. Strips should be removed from the container immediately before use, and the container should be closed promptly. Expired strips should never be used. The chemical reagents degrade over time, and the accuracy of the test is compromised. The expiration date should be checked before each use. ### Reagent Strip Technique The technique used to apply urine to the reagent strip is critical. The strip should be completely immersed in the urine sample, ensuring that all pads are wet. The strip should be removed immediately and the excess urine should be blotted on a clean, absorbent paper towel. The strip should not be shaken or tapped to remove excess urine, as this can cause cross-contamination between pads. The timing of the reading is critical. Each pad has a specific reading time, typically 30 to 60 seconds. Reading too early or too late can produce false results. The manufacturer instructions should be followed precisely. ### Instrument Calibration and Quality Control Automated urine analyzers are used in many veterinary practices. These instruments require regular calibration and quality control. The instrument should be calibrated according to the manufacturer's instructions. Quality control materials should be run at regular intervals to ensure the instrument is performing correctly. The instrument should be cleaned and maintained according to the manufacturer's instructions. The reagent strips used in the instrument should be stored and handled as described above. The instrument should be checked for errors, and the results should be reviewed by a qualified professional. ## Chemical Artifacts Chemical artifacts are false results from the chemical reactions in the reagent strip. These can be from interfering substances in the urine or from the reagent itself. ### Protein The protein reagent pad is based on the principle of the protein error of indicators. The pad is most sensitive to albumin and less sensitive to globulins and Bence Jones proteins. A false positive protein result can be caused by a highly alkaline urine, which can be from bacterial infection or improper storage. A false positive can also be caused by contamination with quaternary ammonium compounds, which are found in some disinfectants. A false negative protein result can be caused by a dilute urine, which dilutes the protein concentration below the detection limit. A false negative can also be caused by a highly acidic urine, which can affect the reagent. ### Glucose The glucose reagent pad is specific for glucose. It is not affected by other sugars. A false negative glucose result can be caused by a high concentration of ascorbic acid, which is vitamin C. Ascorbic acid is a reducing agent that can interfere with the glucose oxidase reaction. A false negative can also be caused by a urine that is not fresh, as bacteria consume glucose. A false positive glucose result is rare but can occur with the use of certain oxidizing agents, such as hydrogen peroxide, which can be present in some urine samples. ### Ketones The ketone reagent pad detects acetoacetic acid and acetone. It does not detect beta-hydroxybutyrate, which is the most common ketone in diabetic ketoacidosis. A false positive ketone result can be caused by a highly colored urine, which can interfere with the color change. A false positive can also be caused by the presence of certain drugs, such as captopril or levodopa. A false negative ketone result can occur if the urine is not fresh, as the ketones are volatile and can evaporate. A false negative can also occur if the urine is highly acidic. ### Blood The blood reagent pad detects hemoglobin and myoglobin. It is a sensitive test that can detect small amounts of blood. A false positive blood result can be caused by the presence of myoglobin, which can be present in the urine after muscle injury. A false positive can also be caused by the presence of oxidizing agents, such as hypochlorite, which can be present in the urine. A false negative blood result can be caused by a high concentration of ascorbic acid, which can interfere with the reaction. A false negative can also be caused by a urine that is not fresh, as the red blood cells can lyse and the hemoglobin can be degraded. ### Bilirubin The bilirubin reagent pad is specific for conjugated bilirubin. A false positive bilirubin result can be caused by the presence of a drug, such as a phenazopyridine, which can color the urine. A false positive can also be caused by a highly colored urine, which can interfere with the reading. A false negative bilirubin result can occur if the urine is not fresh, as bilirubin is light-sensitive and can be degraded. A false negative can also occur if the urine is exposed to light. ### Urobilinogen The urobilinogen reagent pad is not a reliable test. It is affected by many factors, including the pH of the urine, the concentration of the urine, and the presence of other substances. A false positive urobilinogen result can be caused by a highly colored urine. A false negative can be caused by a urine that is not fresh. ### Nitrite The nitrite reagent pad detects the presence of nitrite, which is produced by bacteria that reduce nitrate to nitrite. A false negative nitrite result can be caused by a urine that is not fresh, as the bacteria can convert nitrite to nitrogen. A false negative can also be caused by a urine that is not in the bladder for a sufficient time, as the bacteria need time to convert nitrate to nitrite. A false positive nitrite result is rare but can occur if the urine is contaminated with a substance that contains nitrite. ### Leukocyte Esterase The leukocyte esterase reagent pad detects the presence of white blood cells. A false positive leukocyte esterase result can be caused by a presence of a contaminant, such as a vaginal discharge. A false negative can be caused by a urine that is not fresh, as the white blood cells can lyse and the esterase can be degraded. ## Microscopic Artifacts Microscopic examination of urine sediment is a critical component of urinalysis. The sediment is examined for cells, casts, crystals, and other elements. Artifacts can be introduced during the preparation and examination of the sediment. ### Centrifugation and Sediment Preparation The urine sample should be centrifuged at a standard speed and time, typically 1500 to 2000 revolutions per minute for 5 minutes. The supernatant is decanted, and the sediment is resuspended in a small amount of urine. The sediment is then placed on a slide and covered with a coverslip. The volume of urine used for centrifugation and the volume of the sediment resuspended can affect the concentration of the sediment. A standard protocol should be used to ensure consistency. ### Cellular Degradation Red blood cells, white blood cells, and casts are fragile and can be degraded by time, temperature, and pH. Red blood cells can lyse in a dilute urine or a urine that is not fresh. White blood cells can lyse in a dilute urine or a urine that is not fresh. Casts can dissolve in a dilute urine or a urine that is not fresh. The degradation of cells can lead to false negative results. The presence of a degraded cell can be difficult to identify and can be misinterpreted. ### Crystals Crystals are a common finding in urine sediment. They can be caused by a variety of factors, including the concentration of the urine, the pH of the urine, and the temperature of the urine. Crystals can be a normal finding or a pathological finding. The presence of crystals can be an artifact of the storage. The urine that is refrigerated can form crystals that are not present in the fresh urine. The urine that is allowed to stand at room temperature can form crystals that are not present in the fresh urine. ### Bacteria Bacteria can be present in the urine sediment. They can be a true finding, indicating a urinary tract infection, or they can be a contaminant. The presence of bacteria in a free catch sample can be a contaminant from the distal urethra or the environment. The presence of bacteria in a cystocentesis sample is more likely to be a true finding. The presence of bacteria can be an artifact of the storage. The urine that is not fresh can have bacterial overgrowth, which can be misinterpreted as a urinary tract infection. ## Quality Control and Quality Assurance Quality control and quality assurance are essential for the accuracy of urinalysis. The laboratory should have a quality control program that includes the use of control materials, the calibration of instruments, and the training of personnel. ### Control Materials Control materials are used to monitor the accuracy of the reagent strips and the instruments. The control materials should be run at regular intervals, typically daily. The control materials should be run at two levels, a normal and an abnormal. The results of the control materials should be recorded and reviewed. ### Calibration and Maintenance The instruments should be calibrated according to the manufacturer's instructions. The calibration should be performed at regular intervals. The instruments should be maintained according to the manufacturer's instructions. The maintenance should be documented. ### Personnel Training The personnel who perform the urinalysis should be trained in the proper technique. The training should include the collection of the sample, the storage of the sample, the use of the reagent strips, the use of the instrument, and the interpretation of the results. The personnel should be evaluated on a regular basis. ## Common Failure Patterns The following are common failure patterns in urinalysis: ### Delayed Analysis The most common failure pattern is the delayed analysis. The urine is collected and then left at room temperature for an extended period. This leads to the degradation of cells, the growth of bacteria, and the change in pH. The results are inaccurate and can lead to misdiagnosis. ### Improper Storage The urine is collected and stored improperly. The urine is not refrigerated, or the urine is stored for too long. This leads to the same problems as the delayed analysis. ### Reagent Strip Errors The reagent strips are not handled properly. The strips are expired. The strips are not stored properly. The strips are not immersed properly. The strips are not read at the correct time. These errors lead to false results. ### Contamination The urine is contaminated with the environment. The urine is contaminated with the genital tract. The urine is contaminated with the container. This leads to false positive results. ### Misinterpretation The results are misinterpreted. The results are not correlated with the clinical findings. The results are not correlated with the other laboratory tests. This leads to misdiagnosis. ## Limitations and Considerations Urinalysis is a valuable diagnostic tool, but it has limitations. The results should be interpreted in the context of the clinical findings. The results should be correlated with the other laboratory tests. The results should be repeated if they are unexpected. The urine is a dynamic fluid that changes rapidly. The results are only as good as the sample. The sample should be collected and handled properly. The sample should be analyzed promptly. The reagent strips are a screening test. The results should be confirmed with the microscopic examination. The results should be confirmed with the other laboratory tests. ## Professional Escalation Criteria The following are the criteria for the escalation of the urinalysis results: ### Urgent Escalation The following findings should be escalated to the veterinarian immediately: - The presence of a large amount of blood in the urine - The presence of a large amount of protein in the urine - The presence of a large amount of glucose in the urine - The presence of a large amount of ketones in the urine - The presence of a large number of white blood cells in the urine - The presence of a large number of bacteria in the urine - The presence of a large number of casts in the urine ### Routine Escalation The following findings should be escalated to the veterinarian at the next available opportunity: - The presence of a small amount of blood in the urine - The presence of a small amount of protein in the urine - The presence of a small amount of glucose in the urine - The presence of a small amount of ketones in the urine - The presence of a small number of white blood cells in the urine - The presence of a small number of bacteria in the urine - The presence of a small number of casts in the urine ## Welfare and Safety Context The welfare of the animal is the primary concern. The collection of the urine should be performed in a way that minimizes the stress and the discomfort to the animal. The collection of the urine should be performed in a way that is safe for the animal and the handler. The World Organisation for Animal Health provides official guidance on animal health and welfare [6]. The collection of the urine should be performed in accordance with the welfare guidelines. The animal should be handled gently and with care. The safety of the personnel is also a concern. The urine can contain infectious agents. The personnel should wear appropriate personal protective equipment, including gloves and a lab coat. The personnel should wash their hands after handling the urine. ## Practical Implementation Steps The following are the practical steps for the implementation of a urinalysis quality program: 1. **Establish a standard protocol** for the collection, the storage, and the analysis of the urine. 2. **Train the personnel** on the standard protocol. 3. **Use the quality control materials** to monitor the accuracy of the reagent strips and the instruments. 4. **Calibrate the instruments** at the regular intervals. 5. **Maintain the instruments** according to the manufacturer's instructions. 6. **Review the results** of the quality control and the calibration. 7. **Document the results** of the quality control and the calibration. 8. **Review the results** of the urinalysis with the veterinarian. ## Records and Measurements The following records should be maintained for the urinalysis: - The date and the time of the collection - The method of the collection - The name of the person who collected the sample - The date and the time of the analysis - The name of the person who analyzed the sample - The results of the reagent strip - The results of the microscopic examination - The results of the quality control - The results of the calibration The records should be kept in a secure location. The records should be kept for a period of time as required by the regulations. ## A Structured Artifact Triage Protocol for Urinalysis Result Verification A recurring problem in veterinary practice is not the failure to recognize that artifacts exist, but the absence of a systematic method to decide whether a specific abnormal result is genuine or artifactual before acting on it. Clinicians often face a single abnormal reagent strip reading and must choose between repeating the test, performing additional diagnostics, or initiating treatment. Without a structured approach, the decision becomes subjective and inconsistent. A practical decision framework, built on the artifact categories already described, provides a repeatable method to classify the confidence level of any urinalysis result and determine the next action. ### The Three Question Verification Sequence Before any abnormal urinalysis result is acted upon, the clinician should answer three questions in a fixed order. This sequence forces the evaluation of the most common and most preventable artifact sources first, before considering biological explanations. **Question 1: Was the sample handled correctly?** This question addresses the preanalytical phase. The clinician must verify the collection method, the time between collection and analysis, the storage temperature, and the container type. If the sample was collected by free catch, contamination is possible. If the sample sat at room temperature for more than 30 minutes, cellular degradation and bacterial overgrowth are expected. If the sample was refrigerated, crystal formation and pH changes are possible. If the sample was collected more than 6 hours before analysis, even with refrigeration, the reliability of cellular and chemical measurements is reduced. The Merck Veterinary Manual provides authoritative background on the clinical application of urinalysis and the importance of sample handling for accurate results [4]. When any of these conditions are present, the abnormal result should be considered unverified until a fresh sample is analyzed. **Question 2: Was the reagent strip used correctly?** This question addresses analytical artifacts. The clinician must verify the strip was not expired, was stored in a sealed container, was not touched on the reagent pads, was fully immersed, was blotted to remove excess urine, and was read at the correct time interval. The strip container should be checked for the expiration date and for the presence of the desiccant packet. If the strip was exposed to moisture or heat, the reagents may have degraded. If the reading was taken too early or too late, the color change may not reflect the true concentration. If any of these conditions are present, the result should be repeated with a new strip from a properly stored container. **Question 3: Are there interfering substances or patient factors?** This question addresses chemical artifacts and patient-specific factors. The clinician must review the patient medication list for substances known to interfere with reagent strip tests. Ascorbic acid, or vitamin C, can cause false negative glucose and blood results. Phenazopyridine can cause false positive bilirubin results. Captopril and levodopa can cause false positive ketone results. The urine pH and specific gravity should also be considered. A highly alkaline urine can cause a false positive protein result. A dilute urine can cause false negative results for protein, glucose, and cells. If any of these factors are present, the result should be interpreted with caution and confirmed with a different method. ### The Confidence Level Matrix After the three questions are answered, the clinician assigns a confidence level to the abnormal result. This matrix provides a structured way to categorize the result and determine the next action. | Confidence Level | Criteria | Recommended Action | |---|---|---| | High confidence | Sample handled correctly, strip verified, no interfering substances | Result is likely genuine, proceed with clinical interpretation | | Moderate confidence | One minor issue identified, such as a slightly delayed analysis or a single medication with known interference | Repeat the test on a fresh sample or use a confirmatory test before making clinical decisions | | Low confidence | Multiple issues identified, such as a free catch sample left at room temperature for 2 hours with an expired strip | Discard the result, collect a new sample, and repeat the entire urinalysis | The confidence level is not a substitute for clinical judgment. It is a tool to ensure that the clinician has considered the most common artifact sources before acting on a result. The American Animal Hospital Association provides guidance on preventive care protocols for companion animals, including diagnostic testing recommendations [2]. The confidence level should be recorded in the patient record along with the urinalysis results. ### Confirmatory Testing Pathways When a result is assigned a moderate or low confidence level, the clinician should select a confirmatory test based on the specific analyte in question. The confirmatory test should be chosen to detect the same substance using a different method that is not subject to the same artifact. **Protein confirmation.** If the reagent strip protein result is questionable, the clinician should perform a sulfosalicylic acid turbidity test. This test is not affected by urine pH or the presence of quaternary ammonium compounds. The sulfosalicylic acid test detects all proteins, including globulins, while the reagent strip is most sensitive to albumin. A positive sulfosalicylic acid test with a negative reagent strip may indicate the presence of globulins or Bence Jones proteins. **Glucose confirmation.** If the reagent strip glucose result is questionable due to possible ascorbic acid interference, the clinician should use a glucose test based on a different principle. A copper reduction test, such as the Clinitest, is not affected by ascorbic acid. However, the copper reduction test is not specific for glucose and can detect other reducing substances. The clinician should interpret the result in the context of the patient's clinical signs. **Blood confirmation.** If the reagent strip blood result is questionable, the clinician should perform a microscopic examination of the urine sediment. The presence of red blood cells on the sediment confirms the reagent strip result. If the reagent strip is positive but no red blood cells are seen on the sediment, the result may be due to hemoglobin or myoglobin. Hemoglobinuria can occur with intravascular hemolysis, and myoglobinuria can occur with muscle injury. **Bacteria confirmation.** If the reagent strip nitrite is positive or the sediment shows bacteria, the clinician should perform a urine culture. The culture is the gold standard for the diagnosis of a urinary tract infection. The culture should be performed on a sample collected by cystocentesis to avoid contamination from the distal urethra and genital tract. **Crystal confirmation.** If the sediment shows crystals, the clinician should consider the storage conditions. If the sample was refrigerated, the crystals may be an artifact of the cold temperature. The clinician should warm the sample to room temperature and re-examine the sediment. If the crystals persist, they may be genuine. The type of crystal should be identified to determine if it is clinically significant. ### The Repeat Sample Protocol When a result is assigned a low confidence level, the clinician should collect a new sample and repeat the urinalysis. The repeat sample should be collected using the most appropriate method for the clinical question. For routine screening, a free catch sample may be adequate. For suspected urinary tract infection, cystocentesis is preferred. The repeat sample should be analyzed within 30 minutes of collection. If the repeat sample is not possible, the clinician should document the limitation and interpret the original result with caution. The repeat sample protocol should include a specific gravity measurement. The specific gravity is a measure of the concentration of the urine. A dilute urine can cause false negative results for protein, glucose, and cells. A concentrated urine can cause false positive results for crystals. The specific gravity should be interpreted in the context of the patient's hydration status and renal function. ### The Decision Log A decision log is a record of the artifact assessment for each abnormal urinalysis result. The log should include the patient identification, the date and time of collection, the collection method, the date and time of analysis, the abnormal result, the answers to the three questions, the confidence level, and the action taken. The log provides a record of the clinical reasoning and can be used for quality improvement. The log should be reviewed regularly to identify patterns of artifact occurrence. For example, if the log shows a high number of low confidence results from free catch samples, the practice may need to improve its collection technique. If the log shows a high number of false positive protein results, the practice may need to review its reagent strip storage and handling. The log is a tool for continuous improvement of the urinalysis process. The World Organisation for Animal Health provides official guidance on animal health and welfare, including the importance of accurate diagnostic testing for disease surveillance and control [6]. The sample log is a component of a quality assurance program that supports accurate diagnostic testing. ### Integration with Clinical Decision Making The decision framework is not a replacement for clinical judgment. It is a tool to help the clinician make a more informed decision. The framework should be used in the context of the patient's clinical signs, history, and other laboratory results. A result that is assigned a high confidence level but does not fit the clinical picture should still be questioned. A result that is assigned a low confidence level but is consistent with the clinical picture should not be ignored. The framework is designed to be practical and efficient. The three questions can be answered in less than a minute. The confidence level can be assigned in a few seconds. The confirmatory tests are standard laboratory procedures. The framework does not require additional equipment or specialized training. The World Small Animal Veterinary Association provides global guidelines for companion animal clinical practice, including diagnostic testing and preventive care [3]. The decision framework aligns with these guidelines by promoting a systematic approach to diagnostic testing and clinical decision-making. ### Common Failure Patterns in the Decision Framework The decision framework is only effective if it is used consistently. The following are common failure patterns in the application of the framework: **Skipping the three questions.** The clinician may be tempted to skip the three questions and proceed directly to the confidence level. This defeats the purpose of the framework. The three questions are the core of the framework and should be answered for every abnormal result. **Assigning a high confidence level too quickly.** The clinician may assign a high confidence level to a result that has a minor issue. For example, the clinician may assign a high confidence level to a result from a sample that was analyzed at 45 minutes instead of 30 minutes. The framework should be applied strictly. If the sample was not analyzed within 30 minutes, the confidence level should be moderate at best. **Failing to document the decision.** The clinician may make a decision but fail to document the reasoning. The documentation is essential for the quality improvement process. The documentation should include the answers to the three questions and the confidence level. **Using the wrong confirmatory test.** The clinician may use a confirmatory test that is subject to the same artifact as the original test. For example, the clinician may repeat the reagent strip glucose test to confirm a glucose result that was affected by vitamin C. The confirmatory test should be based on a different principle. **Failing to repeat the sample.** The clinician may not collect a new sample when the confidence level is low. This can lead to a misdiagnosis. The repeat sample is essential for the accuracy of the result. ### The Role of the Veterinarian The decision framework is designed for use by the entire clinical team, including veterinary technicians and assistants. The veterinarian is responsible for the final interpretation of the results and the clinical decision. The veterinarian should review the confidence level and the action taken. The veterinarian should also review the sample log to identify patterns of artifact errors. The veterinarian should provide training to the clinical team on the use of the framework. The training should include the three questions, the confidence level matrix, and the confirmatory tests. The training should be repeated at regular intervals to ensure that the team is using the framework correctly. The veterinarian should also be aware of the limitations of the framework. The framework does not address all possible artifacts. The framework is a tool for the most common artifacts. The veterinarian should use clinical judgment to identify and address any other artifacts that may be present. ### The Framework in Practice The following is an example of the framework in practice. A dog is presented for a wellness examination. A free catch urine sample is collected and analyzed within 30 minutes. The reagent strip shows a positive protein result. The clinician answers the three questions. The sample was collected by free catch, which is a potential source of contamination. The sample was analyzed within 30 minutes, which is correct. The reagent strip was not expired and was handled correctly. The patient is not on any medications that interfere with the protein test. The urine pH is 7.5, which is slightly alkaline. The clinician assigns a moderate confidence level to the protein result. The clinician performs a sulfhydrate acid turbidity test, which is positive. The clinician also performs a microscopic examination of the sediment, which shows no red blood cells or white blood cells. The clinician concludes that the protein is genuine and may be due to early kidney disease. The clinician recommends a repeat urinalysis in 2 weeks and a blood chemistry panel to assess renal function. This example demonstrates the use of the framework. The clinician did not immediately interpret the protein result as kidney disease. The clinician considered the artifact sources, assigned a confidence level, and performed a confirmatory test. The clinician then made a clinical decision based on the confirmed result. The decision framework is a practical tool for the veterinary practice. It is a systematic method for the evaluation of abnormal urinalysis results. It is designed to be efficient and to improve the accuracy of the diagnostic process. The framework should be used consistently by the entire clinical team. The framework should be reviewed and updated as new information becomes available. ## Frequently Asked Questions ### What is the most common cause of urinalysis artifacts? The most common cause is the delayed analysis of the urine sample. When urine sits at room temperature, cells degrade, bacteria multiply, and pH shifts, leading to false results. Analyze urine within 30 minutes of collection or refrigerate it and analyze within 24 hours. ### How long can urine be refrigerated before analysis? Refrigerated urine can be analyzed within 24 hours, but the sample should be allowed to return to room temperature and be thoroughly mixed before analysis. Refrigeration slows bacterial growth and cellular degradation but does not stop it, and it can cause crystal formation. ### Can vitamin C cause a false negative glucose result? Yes, ascorbic acid, or vitamin C, can interfere with the glucose oxidase reaction on the reagent strip, causing a false negative glucose result. This is more common in patients receiving high doses of vitamin C supplements. ### How can I prevent contamination in a free catch urine sample? To minimize contamination, clean the perineal area before collection, use a sterile container, and collect a midstream sample. For the most accurate culture results, cystocentesis is the preferred method. ### What does a false positive protein result mean? A false positive protein result can be caused by a highly alkaline urine, a contaminated sample, or the presence of disinfectants. It does not necessarily indicate kidney disease. Confirm the result with a microscopic examination and a repeat test. ### Why are casts not seen in a urine sample? Casts are fragile and can dissolve in a dilute urine or a urine that is not fresh. They can also be missed if the sample is not centrifuged properly. The absence of casts does not rule out kidney disease. ### What is the difference between a false positive and a false negative? A false positive result indicates that a substance is present when it is not. A false negative result indicates that a substance is absent when it is present. Both can be caused by artifacts and can lead to misdiagnosis. ### When should I escalate an abnormal urinalysis result to a veterinarian? Any abnormal result should be discussed with a veterinarian. Urgent findings include a large amount of blood, protein, glucose, ketones, white blood cells, bacteria, or casts in the urine. The veterinarian will determine the next steps. ## Related Veterinary Guides - [Urinalysis in Veterinary Practice: From Collection to Interpretation](/knowledge/veterinary-medicine/clinical-pathology/urinalysis-veterinary-practice-collection-interpretation) - [Cytology versus Biopsy in Veterinary Patients: Sample Choice, Handling, Limitations, and Escalation](/knowledge/veterinary-medicine/clinical-methods/cytology-versus-biopsy-veterinary-sample-choice-handling-limitations-escalation) - [Syndromic Surveillance in Veterinary Practice](/knowledge/veterinary-medicine/veterinary-epidemiology/syndromic-surveillance-veterinary-practice) - [Electrosurgery and Vessel Sealing in Veterinary Practice](/knowledge/veterinary-medicine/veterinary-surgery/electrosurgery-and-vessel-sealing-in-veterinary-practice) - [Veterinary Clinical Skills Models for Practice](/knowledge/veterinary-medicine/clinical-skills-training/veterinary-clinical-skills-models-practice) ## 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. - [Artifactually increased serum bicarbonate in a cat with rhabdomyolysis.](https://pubmed.ncbi.nlm.nih.gov/38872478). Veterinary clinical pathology, 2024. - [Ultrasonographic characteristics of lipiduria in clinically normal cats.](https://pubmed.ncbi.nlm.nih.gov/24102935). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2014. - [Urine concentrations of ketamine and norketamine following illegal consumption.](https://pubmed.ncbi.nlm.nih.gov/11599604). Journal of analytical toxicology, 2001. - [Twinkling artifact in small animal color-Doppler sonography.](https://pubmed.ncbi.nlm.nih.gov/16863058). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2006. - [Understanding the Progression of Chronic Kidney Disease in Cats: From Pathophysiology to Emerging Biomarkers.](https://doi.org/10.3390/vetsci13020199). 2026. > This article is educational and is not a substitute for veterinary diagnosis or treatment. Contact a veterinarian for advice about an individual animal.