Laboratory Audits: A Practical Guide to Internal and External Assessments

Laboratory audits are systematic, documented reviews of laboratory performance against established standards, and they serve as a core mechanism for continuous quality improvement in diagnostic services. This guide provides laboratory students, technicians, researchers, and diagnostic professionals with a practical framework for conducting internal audits and preparing for external assessments, including step-by-step processes, checklists, and corrective action templates.

At a Glance

Laboratory audits measure performance against standards that should be established using evidence-based principles. When gaps are found, changes are implemented and a re-audit is performed after a defined period to confirm improvements have been maintained. The table below summarizes the key audit types, their primary purposes, and the personnel typically involved.

Understanding the Purpose and Scope of Laboratory Audits

Audits are part of the continuous quality improvement process and one of the key elements of clinical governance. Laboratory-based clinical audits focus on everyday aspects of laboratory services and provide feedback to both laboratory staff and service users. They involve measuring laboratory performance against established standards, which should ideally be developed using evidence-based medicine principles. If deficiencies are identified, changes are implemented and a re-audit is performed after a certain time period to ensure the changes have been implemented and maintained. Areas of audit in the laboratory include the preanalytical, analytical, and postanalytical phases.

Audit in laboratory medicine may be defined as a process of review and assessment of laboratory performance, and its purpose should be to improve patient care by enhancing laboratory performance and making better use of resources. The rationale for audit includes identifying inefficiencies, reducing errors, and ensuring that laboratory services align with clinical needs. The goals of audit extend beyond compliance checking to include consultative activities, participation in interdisciplinary teams, and efforts to assure appropriate test utilization.

The scope of an internal audit should cover all elements of the quality management system, including management responsibilities, document control, personnel competence, equipment maintenance, reagent management, preanalytical processes, analytical procedures, postanalytical reporting, and customer feedback. For laboratories pursuing accreditation, the audit scope must align with the requirements of the relevant standard, such as ISO 15189.

Core Principles of Effective Auditing

Effective auditing rests on several foundational principles that ensure the process is objective, systematic, and valuable for quality improvement.

Independence and Objectivity

Auditors must be independent of the activities they assess. This means that an auditor should not audit their own work. In small laboratories where staffing is limited, this can be challenging, but it can be addressed by training multiple staff members as auditors and arranging cross-audits between sections or by outsourcing the internal audit to external auditors with expertise in audit methodology and knowledge of biological standards. One medical laboratory preparing for accreditation by the French Accreditation Committee outsourced its internal audit to auditors who had expertise in audit, comprehensive knowledge of biological standards, and independence from the laboratory's daily operations.

Evidence-Based Standards

Audit criteria should be derived from established standards, standard operating procedures, and regulatory requirements. Standards should be set using laboratory standard operating procedures, and practice should be observed using purpose-designed questionnaires. The use of evidence-based standards ensures that audits measure meaningful aspects of laboratory performance instead of arbitrary criteria. Evidence-based laboratory medicine combines methods from epidemiology, biostatistics, clinical and social sciences with basic sciences to evaluate the role of investigations in clinical decision making and outcomes for patients.

Systematic Process

A structured approach to auditing ensures consistency and completeness. The audit process should follow a defined cycle that includes planning, conducting, reporting, and following up on corrective actions. One microbiology laboratory established a model of laboratory-based process audit where laboratory activities were examined in turn by specimen type, standards were set using standard operating procedures, practice was observed using a purpose-designed questionnaire, data were analyzed by computer, performance was assessed at laboratory audit meetings, and the audit circle was closed by re-auditing topics after an interval. This model produced improvements in performance scores and staff morale.

Risk-Based Thinking

Modern quality management standards emphasize risk-based thinking in audit planning. This means that audit frequency and depth should be proportional to the risk associated with each process or activity. High-risk processes, such as blood transfusion testing or microbiology culture of sterile sites, may require more frequent audits than lower-risk activities. Risk management concepts applied to the audit process include process approach, root cause analysis, and effects and criticality analysis.

Planning an Internal Audit Program

A well-designed audit program is the foundation of effective internal auditing. The audit program should be documented and should specify the scope, frequency, methods, responsibilities, and resource requirements for audits over a defined period.

Defining the Audit Program

The audit program should cover all processes and activities within the laboratory's quality management system. When developing the program, consider the following elements:

• The scope of the quality management system, including all testing areas and support functions
• The requirements of applicable standards and regulations
• The results of previous audits and the status of corrective actions
• Quality indicators and performance data that may identify high-risk areas
• Changes in laboratory operations, personnel, or equipment
• Customer complaints and feedback

The audit program should be reviewed periodically and updated based on changes in the laboratory's risk profile and quality performance.

Selecting and Training Auditors

Internal auditors should have appropriate training in audit principles, techniques, and the standards against which they will audit. They should also have sufficient technical knowledge of the processes they will assess. Auditor training should cover:

• Audit planning and preparation
• Interviewing techniques
• Observation and documentation review skills
• Root cause analysis and corrective action verification
• Report writing and communication

In laboratories with limited resources, training a small team of auditors who can cross-audit different sections is often more practical than relying on a single individual. The use of electronic audit tools can reduce workload and language barriers and facilitate analysis of results across multiple sites.

Developing Audit Criteria and Checklists

Audit checklists translate standards and procedures into specific, verifiable criteria. A well-designed checklist ensures that auditors cover all relevant requirements consistently. The checklist should include:

• The requirement or standard being assessed
• The evidence to be reviewed, such as documents, records, or observations
• Space for recording findings and observations
• A mechanism for rating compliance, such as conforming, nonconforming, or observation

For equipment-specific audits, checklists can be developed by identifying relevant conformance requirements from management and technical clauses of the applicable standard, manufacturer requirements, and specific requirements for accreditation. One study identified conformance requirements associated with the hardware and software components of a specific analyzer and used these to develop conformity evaluation checklists and an interpretation checklist to support the internal audit process.

Conducting the Internal Audit

The audit itself involves a structured sequence of activities designed to gather objective evidence of laboratory performance.

Opening Meeting

The audit should begin with an opening meeting between the audit team and the laboratory management or section heads. The purpose of the opening meeting is to:

• Confirm the scope and objectives of the audit
• Review the audit schedule and logistics
• Clarify roles and responsibilities
• Establish communication channels
• Address any concerns or questions from the auditees

Evidence Collection

Auditors gather evidence through three primary methods: document review, observation of practice, and interviews with staff. Each method provides different types of evidence, and effective audits use all three in combination.

Document review involves examining policies, procedures, standard operating procedures, records, and other documentation to verify that the laboratory has defined its processes and that records are being maintained. Observation involves watching laboratory staff perform their duties to verify that practice matches documented procedures. Interviews allow auditors to assess staff understanding of procedures and to identify areas where training may be needed.

A baseline audit in a medical laboratory involved 30 multidisciplinary healthcare providers and used audit criteria with data collected through direct observation, interviews with participants, and checking of records. This approach identified gaps in communication training and led to the implementation of a workshop focused on communication to address identified barriers.

Recording Findings

All audit findings should be recorded objectively and factually. Findings should be classified according to their severity and impact on laboratory quality. Common classifications include:

• Conformity: The process or activity meets the audit criteria
• Nonconformity: The process or activity does not meet the audit criteria
• Observation: A potential weakness or area for improvement that does not currently constitute a nonconformity

Each nonconformity should be documented with sufficient detail to allow the auditee to understand the issue and take corrective action. The documentation should include the specific requirement that was not met, the evidence of the nonconformity, and the location or context where it was observed.

Closing Meeting

The audit should conclude with a closing meeting where the audit team presents the findings to laboratory management. The closing meeting provides an opportunity to:

• Summarize the audit findings and conclusions
• Discuss any disagreements or clarifications
• Agree on timelines for corrective actions
• Confirm the distribution of the audit report

Audit Findings and Corrective Action Template

A standardized template for documenting audit findings and corrective actions ensures consistency and facilitates follow-up. The following template can be adapted for use in any laboratory.

When a nonconformity is identified, the laboratory should conduct a root cause analysis to determine why the issue occurred. Root cause analysis techniques include the five whys, fishbone diagrams, and failure mode and effects analysis. The corrective action should address the root cause instead of only the symptoms of the problem.

Preparing for External Assessments

External assessments, such as accreditation inspections or regulatory visits, require thorough preparation to demonstrate that the laboratory's quality management system is effective and sustainable.

Gap Analysis

Before an external assessment, the laboratory should conduct a gap analysis to compare its current practices against the requirements of the relevant standard. A gap analysis involves reviewing each requirement and determining whether the laboratory currently meets it, partially meets it, or does not meet it. The results of the gap analysis inform the development of an action plan to address identified gaps.

One research program implementing ISO 15189 conducted an initial gap analysis before implementing its quality management system and then conducted a second gap analysis during the transition to an updated version of the standard, with emphasis on risk-based thinking and alignment with patient-centered requirements. The gap analysis approach allowed the laboratory to prioritize its efforts and allocate resources effectively.

Document Review

External assessors will review the laboratory's documentation to verify that the quality management system is properly defined and implemented. The laboratory should ensure that:

• All documents are current, approved, and controlled
• Standard operating procedures are available at the point of use
• Records are complete, legible, and retrievable
• Document changes are properly authorized and recorded

Staff Preparation

Staff should be prepared for the external assessment through training and mock audits. Staff should understand:

• The purpose and scope of the external assessment
• The standards and requirements being assessed
• Their roles and responsibilities during the assessment
• How to respond to assessor questions accurately and confidently

Effective communication is the basis of all interpersonal actions, and optimal and efficient communication needs permanent awareness and training. The healthcare industry is a constantly changing field, so communication becomes a very important tool that contributes to change. Preparing staff for external assessments should include communication training to ensure they can interact effectively with assessors.

Facility and Equipment Readiness

The laboratory should verify that facilities and equipment are ready for inspection. This includes:

• Confirming that equipment is calibrated, maintained, and functioning properly
• Ensuring that temperature monitoring systems are operational and records are current
• Verifying that reagents and consumables are within their expiry dates and stored correctly
• Confirming that waste management procedures are being followed
• Ensuring that safety equipment, such as fire extinguishers and eyewash stations, is accessible and functional

Common Failure Patterns in Laboratory Audits

Understanding common failure patterns can help laboratories focus their audit preparation and corrective action efforts on areas that are frequently problematic.

Preanalytical Errors

Preanalytical errors are among the most common findings in laboratory audits. These include sample labeling discrepancies, incomplete documentation, and sample quality issues. An audit of Group and Save samples in a United Kingdom district hospital found that 37.4% of samples were rejected, with the majority taken by accident and emergency staff. Predominant causes were absent signatures, missing date and time, mismatched identifiers, and sample integrity issues such as haemolysis or underfilling. Approximately 20% of affected patients required two or more repeat samples, and the direct cost per rejected sample ranged from 12 to 80 pounds. After interventions, a re-audit showed the rejection rate fell to 16.6%.

Inadequate Documentation

Documentation failures are frequently identified during audits. These may include incomplete records, missing signatures, outdated procedures, or uncontrolled documents. Documentation failures can affect all phases of laboratory testing and can have serious consequences for patient care and laboratory accreditation.

Equipment Maintenance Gaps

Audits often identify gaps in equipment maintenance, including missing calibration records, expired calibration certificates, or failure to perform scheduled preventive maintenance. Equipment-related nonconformities can affect the accuracy and reliability of test results and may require immediate corrective action.

Training and Competency Gaps

Audits may reveal that staff have not received adequate training or that competency assessments are not being performed regularly. Training gaps can lead to errors in testing and reporting and may indicate weaknesses in the laboratory's human resource management.

Communication Barriers

Communication failures between laboratory staff and healthcare providers can be identified through audits. A best practice implementation project found that lack of time for team briefings and interactions led to different points of view among healthcare providers. The project demonstrated that a structured communication improvement strategy, including training sessions, could improve compliance with audit criteria and enhance team cohesion.

Records and Measurements for Audit Programs

Effective audit programs rely on accurate records and meaningful measurements to track performance and demonstrate improvement.

Essential Audit Records

The laboratory should maintain the following records related to its audit program:

• The audit program and schedule
• Audit plans and checklists
• Audit reports and findings
• Corrective action requests and verification records
• Management review minutes that discuss audit results
• Training records for auditors

Quality Indicators

Quality indicators are measurable parameters that reflect the performance of laboratory processes. Common quality indicators include:

• Sample rejection rate
• Turnaround time for critical tests
• Error rates in result reporting
• Customer satisfaction scores
• Proficiency testing performance
• Corrective action completion rates

Quality indicators should be established to monitor performance and should be reviewed regularly to identify trends and areas for improvement. During the implementation of a quality management system, quality indicators were established to monitor performance and support continuous improvement.

Audit Frequency and Coverage

The audit program should specify the frequency of audits for each area or process. The frequency should be based on the risk associated with the process, the history of nonconformities, and the significance of the process to patient care. High-risk processes may require audits more frequently than once per year, while lower-risk processes may be audited less frequently.

Practical Steps for Implementing an Audit Program

Implementing an effective audit program requires a systematic approach that engages staff and leadership.

Step 1: Secure Leadership Commitment

Leadership engagement is essential for the success of an audit program. Laboratory management must demonstrate commitment to quality improvement by allocating resources for audits, supporting auditor training, and acting on audit findings. A quality officer should be appointed to oversee the audit process, supported by leadership engagement and staff training to establish core competencies.

Step 2: Conduct an Initial Gap Analysis

Before implementing the audit program, conduct a gap analysis to understand the current state of the laboratory's quality management system. This analysis will help prioritize audit activities and identify areas where the laboratory is at risk of nonconformity.

Step 3: Develop the Audit Program and Schedule

Create a documented audit program that covers all processes and activities within the laboratory's scope. The program should specify the frequency of audits, the responsibilities of auditors, and the methods to be used.

Step 4: Train Internal Auditors

Select and train internal auditors who have the knowledge and skills to conduct effective audits. Training should cover audit principles, techniques, and the specific standards and requirements applicable to the laboratory.

Step 5: Conduct Audits According to Schedule

Execute the audit program according to the defined schedule. Ensure that audits are conducted objectively and that findings are documented accurately.

Step 6: Report Findings and Implement Corrective Actions

Distribute audit reports to relevant stakeholders and manage corrective actions through a formal process. Each nonconformity should have a root cause analysis, a corrective action plan, a responsible person, and a target completion date.

Step 7: Verify Effectiveness and Re-audit

After corrective actions have been implemented, verify that they have been effective in addressing the root cause. Re-audit the area after a defined period to confirm that improvements have been maintained.

Step 8: Review the Audit Program

Periodically review the audit program to ensure it remains effective and relevant. The review should consider changes in laboratory operations, new or revised standards, and the results of previous audits.

Limitations of Laboratory Audits

While audits are a powerful tool for quality improvement, they have limitations that laboratory professionals should understand.

Snapshot in Time

An audit provides a snapshot of laboratory performance at a specific point in time. It cannot guarantee that performance is consistent between audits. This limitation can be mitigated by increasing audit frequency for high-risk processes and by using quality indicators to monitor performance continuously.

Auditor Subjectivity

Despite efforts to standardize audit processes, some degree of auditor subjectivity is unavoidable. Different auditors may interpret requirements differently or focus on different aspects of laboratory performance. This limitation can be reduced through auditor training, the use of detailed checklists, and the involvement of multiple auditors for complex assessments.

Resource Intensity

Audits require significant resources, including staff time, training, and documentation. For small laboratories with limited resources, maintaining a robust audit program can be challenging. Electronic audit tools can reduce workload and facilitate analysis of results, making the audit process more efficient.

Focus on Compliance

Audits that focus primarily on compliance with standards may miss opportunities for broader quality improvement. Laboratories should balance compliance-focused audits with other quality improvement activities, such as process improvement projects and customer feedback analysis.

Safety and Regulatory Context

Laboratory audits must consider safety and regulatory requirements as integral components of the quality management system.

Biosafety Considerations

The World Health Organization's Laboratory Biosafety Manual provides guidance on biosafety practices that should be assessed during laboratory audits. Auditors should verify that:

• Laboratory staff are trained in biosafety procedures
• Personal protective equipment is available and used correctly
• Biological waste is managed according to established procedures
• Emergency procedures are documented and practiced
• Laboratory facilities meet biosafety requirements for the types of work performed

Quality Management System Standards

The World Health Organization's Laboratory Quality Management System Handbook provides comprehensive guidance on the components of a quality management system for laboratories. Auditors should use such references to ensure that their audit criteria are aligned with internationally recognized best practices.

Regulatory Compliance

Laboratories must comply with applicable regulations and accreditation requirements. Auditors should verify that the laboratory is aware of and compliant with all relevant regulatory requirements, including those related to test method validation, quality control, and result reporting. The U.S. Food and Drug Administration's Bioanalytical Method Validation Guidance provides requirements for the validation of bioanalytical methods that may be relevant for laboratories performing such testing.

Professional Escalation Criteria

Laboratory professionals should know when to escalate audit findings or quality issues to higher levels of management or external authorities.

Immediate Escalation

The following situations require immediate escalation to laboratory management:

• A nonconformity that poses an immediate risk to patient safety
• Evidence of fraudulent or falsified records
• A critical equipment failure that affects test results
• A safety incident that requires investigation
• A breach of confidentiality or data security

Escalation to External Authorities

Some situations may require escalation to external authorities, such as regulatory bodies or accrediting organizations:

• A serious adverse event related to laboratory testing
• A pattern of nonconformities that suggests systemic quality failures
• An inability to implement corrective actions within agreed timelines
• A request from an external authority for information or investigation

Documentation of Escalation

All escalations should be documented, including the reason for escalation, the individuals involved, and the actions taken. This documentation provides a record of the laboratory's response to quality issues and supports continuous improvement.

Frequently Asked Questions

What is the difference between an internal audit and an external assessment?

An internal audit is conducted by laboratory staff or contracted auditors who are independent of the area being assessed. It evaluates the laboratory's quality management system and technical activities against internal policies and accreditation standards. An external assessment is conducted by an accrediting body or regulatory authority to determine whether the laboratory meets the requirements for accreditation or certification. External assessments are typically more formal and may result in the granting, maintenance, or withdrawal of accreditation status.

How often should internal audits be conducted?

The frequency of internal audits should be defined in the laboratory's audit program and should be based on the risk associated with each process. High-risk processes may require audits more frequently than once per year, while lower-risk processes may be audited less frequently. The audit program should be reviewed periodically and adjusted based on changes in laboratory operations, quality indicators, and the results of previous audits.

Who should perform internal audits?

Internal auditors should be trained in audit principles and techniques and should be independent of the activities they assess. In small laboratories, this may require cross-audits between sections or the use of external auditors. Auditors should have sufficient technical knowledge of the processes they will assess and should be able to communicate findings effectively.

What should be included in an audit checklist?

An audit checklist should include the requirement or standard being assessed, the evidence to be reviewed, space for recording findings, and a mechanism for rating compliance. The checklist should be developed from the applicable standards, standard operating procedures, and regulatory requirements. For equipment-specific audits, checklists can be developed by identifying relevant conformance requirements from management and technical clauses of the applicable standard, manufacturer requirements, and accreditation body requirements.

How should nonconformities be handled after an audit?

Nonconformities should be documented and managed through a formal corrective action process. Each nonconformity should undergo root cause analysis to determine why the issue occurred. A corrective action plan should be developed that addresses the root cause, identifies a responsible person, and sets a target completion date. After implementation, the effectiveness of the corrective action should be verified, and the area should be re-audited after a defined period to confirm that improvements have been maintained.

What is the role of re-audits in the audit cycle?

Re-audits are an essential part of the audit cycle because they verify that corrective actions have been implemented and maintained. A re-audit should be conducted after a defined period following the implementation of corrective actions. The re-audit should focus on the areas where nonconformities were identified and should assess whether the corrective actions have been effective in addressing the root causes.

How can laboratories prepare staff for external assessments?

Staff preparation for external assessments should include training on the purpose and scope of the assessment, the standards and requirements being assessed, and their roles and responsibilities during the assessment. Mock audits can help staff practice responding to assessor questions and become familiar with the assessment process. Communication training is also important because effective communication is the basis of all interpersonal actions and contributes to the quality of health services.

What are the most common findings in laboratory audits?

Common findings in laboratory audits include preanalytical errors such as sample labeling discrepancies and incomplete documentation, inadequate documentation and record keeping, equipment maintenance gaps, training and competency gaps, and communication barriers between laboratory staff and healthcare providers. Understanding these common failure patterns can help laboratories focus their audit preparation and corrective action efforts on areas that are frequently problematic.

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References and Further Reading

• Laboratory Quality Management System Handbook. World Health Organization.
• Laboratory Biosafety Manual. World Health Organization.
• Assay Guidance Manual. National Center for Advancing Translational Sciences.
• Bioanalytical Method Validation Guidance. U.S. Food and Drug Administration.
• NCBI Literature Resources. National Center for Biotechnology Information.
• Communication, an important link between healthcare providers: a best practice implementation project.. JBI evidence implementation, 2022.
• Clinical audit in the laboratory.. Journal of clinical pathology, 2009.
• Audit in laboratory medicine.. European journal of clinical chemistry and clinical biochemistry : journal of the Forum of European Clinical Chemistry Societies, 1996.
• [Evidence-based laboratory medicine].. Orvosi hetilap, 2003.
• [Internal audit in medical laboratory: what means of control for an effective audit process?].. Annales de biologie clinique, 2013.
• SLIPTA e-Tool improves laboratory audit process in Vietnam and Cambodia.. African journal of laboratory medicine, 2014.
• Internal audit in a microbiology laboratory.. Journal of clinical pathology, 1995.
• Establishing a primary care audit and feedback implementation laboratory: a consensus study.. Implementation science communications, 2021.
• Audit of Group and Save Sample Rejection in Fractured Neck of Femur Patients at a United Kingdom District Hospital.. 2026.
• Clinical Audit of Enteric Fever Diagnostic Practices at Kosti Teaching Hospital: A Retrospective Evaluation.. 2026.
• Implementing and Transitioning a Laboratory Quality Management System from ISO 15189:2012 to ISO 15189:2022: Experience from the Malawi-Liverpool Wellcome Research Programme, Blantyre.. 2026.
• Antimicrobial Resistance in Intensive Care Units in Somalia: A Commentary on Measurement Gaps and Facility-Level Priorities for Infection Prevention and Stewardship.. 2026.
• An Integrated Framework for the Implementation and Strengthening of Antimicrobial Stewardship Programs in Six Countries in Latin America.. 2026.
• The road map for ISO 15189-laboratory accreditation: The Experience of Manhiça Health Research Centre (CISM) laboratory, in southern Mozambique. 2026.
• Enrollment Problems and Training Models for Training Postgraduate Students in Clinical Laboratory Diagnosis (Professional Degree) During the "Four Certificates in One" Era in China.. 2026.
• Glucagon-like Peptide-1 Receptor Agonists and Alcohol Use Outcomes: A Systematic Review of Clinical Evidence. 2026.
• Conformity Evaluation of Afinion 2 Analyzer Maintainability: Compliance Practicality for Philippine National Standard PNS ISO 15189:2013 Accreditation. Acta medica Philippina, 2023.
• Terminological clarification of descriptive terms for ISO 15189:2012 evaluation and internal audit processes. 2015.
• Identification of ISO 15189: 2012 conformance requirements for medical laboratory internal auditing. 2015.
• Document review checklists for ISO 15189:2012 internal auditing: An applied tool for medical laboratories. 2016.
• [The accreditation of a surgical pathology and somatic genetic laboratory (LPCE, CHU of Nice) according to the ISO 15189 norm: Sharing of experience].. Annales de Pathologie, 2013.
• ISO 15189:2003 - Quality management, evaluation and continual improvement. Clinical Chemistry and Laboratory Medicine, 2006.
• Audit in laboratory medicine. European Journal of Clinical Chemistry and Clinical Biochemistry, 1996.

This article is educational and does not replace validated laboratory procedures, institutional biosafety review, manufacturer instructions, or professional interpretation.