Understanding WHO PQS: Prequalification of Quality Control Laboratories

Quality control laboratories (QCLs) play a pivotal role in pharmaceutical product safety, efficacy, and regulatory compliance. To ensure consistent, globally recognized standards, the World Health Organization (WHO) established the Prequalification of Quality Control Laboratories (PQS) initiative. This article provides a comprehensive overview of the WHO PQS framework, detailing its scope, inspection requirements, and the strategic value it offers to national regulatory authorities and testing facilities worldwide.

What Is the WHO PQS Programme?

The WHO PQS programme assesses and prequalifies public and private quality control laboratories involved in testing pharmaceutical products, ensuring compliance with WHO-recommended Good Practices for Pharmaceutical Quality Control Laboratories. Prequalified labs are listed in WHO’s global directory and are eligible to test medicines in support of regulatory decisions and international procurement programs.

Objectives of the WHO PQS Initiative:

• Ensure laboratory testing services meet international quality and reliability standards
• Facilitate regulatory reliance on test results from prequalified labs
• Support national medicine regulatory authorities (NRAs) in expanding testing capabilities
• Promote harmonized practices in pharmaceutical quality control

Eligibility Criteria for PQS Application:

• Operational public or private QC labs testing human pharmaceuticals
• Labs operating under documented quality systems aligned with ISO/IEC 17025 and WHO guidelines
• Active participation in proficiency testing (PT) or external quality assurance programs
• Commitment to ongoing compliance and continuous improvement

Applicable WHO Guidelines and References:

• WHO TRS 957 Annex 1 – Good Practices for Pharmaceutical Quality Control Laboratories
• ISO/IEC 17025 – General requirements for the competence of testing and calibration laboratories
• WHO TRS 996 – Good data and record management practices
• WHO PQS Inspection Checklist and Assessment Tool

Key Components of WHO PQS Assessment:

1. Management and Quality Systems

• Organizational structure and independence from manufacturing units
• Quality Manual aligned with ISO/WHO principles
• Defined scope of testing activities and documented SOPs
• Internal audits, risk assessments, and CAPA implementation records

2. Technical Competence and Staffing

• Documented staff qualifications, job descriptions, and ongoing GMP training
• Defined roles for analysts, reviewers, and QA oversight
• Training records on method validation, instrument use, and data integrity

3. Testing Facility and Equipment

• Controlled access to testing zones and sample storage
• Validated instruments with calibration and maintenance logs
• Environmental monitoring data for sensitive testing areas
• Proper storage and handling of reference standards and reagents

4. Analytical Method Management

• Documented method validation protocols and reports
• Transfer of analytical methods with acceptance criteria
• Review of system suitability tests and performance qualification
• Change control for method modifications and upgrades

5. Sample and Data Management

• Sample receipt logs, chain of custody, and retention records
• Secure and validated LIMS or manual documentation systems
• SOPs for raw data handling, result verification, and report issuance
• Data integrity practices in line with ALCOA+ principles

6. Proficiency Testing and Quality Indicators

• Participation in WHO-recognized proficiency testing schemes
• Analysis of root causes for PT failures and CAPA responses
• Internal quality metrics (e.g., retest rates, OOS/OOT trends)

WHO PQS Inspection Workflow:

1. Submission of application dossier including Quality Manual and completed self-assessment form
2. WHO review and eligibility confirmation
3. Scheduling of on-site inspection by WHO and partner agencies
4. Issuance of observation report and required CAPA submission (within 60 days)
5. Review of CAPA and publication of PQ decision and lab listing

Post-Prequalification Commitments:

• Annual reporting of key changes and quality indicators
• Requalification inspection every 3–5 years or as needed
• Maintenance of up-to-date SOPs and documentation systems
• Response to WHO queries and submission of periodic PT results

Benefits of WHO PQS Accreditation:

• Recognition as a reliable QC lab by global procurement agencies
• Participation in quality monitoring of prequalified and donated medicines
• Stronger partnership opportunities with NRAs and UN procurement bodies
• Enhanced credibility and competitiveness in national and international markets

Common Gaps Observed in WHO PQS Inspections:

• Incomplete documentation of method validation or equipment calibration
• Inconsistent logbook entries and lack of data backup systems
• Insufficient trend analysis or corrective action documentation
• Inadequate separation of sample processing and data review roles

Checklist for PQS Inspection Readiness:

1. Update Quality Manual and SOPs per latest WHO TRS
2. Conduct an internal audit mimicking WHO inspection criteria
3. Verify equipment logs, method validation folders, and training files
4. Review data integrity compliance and electronic record policies
5. Prepare sample tracking documentation and retest logs

Conclusion:

Prequalification under WHO’s PQS framework empowers quality control laboratories to support public health objectives and global pharmaceutical oversight. By aligning their quality systems with WHO expectations and maintaining rigorous documentation, labs not only gain recognition but also enhance their capacity to deliver reliable, consistent, and regulatory-trusted analytical results. For both public and private sector labs, PQS is a gateway to excellence in global quality control standards.