Accreditation of Medical Microbiology Laboratories

Ms. Neha Sharma

Introduction

  • Definition:
    Accreditation of Medical Microbiology Laboratories is the formal recognition by an authorized body that a laboratory is competent to perform specific tests. Unlike general certification, accreditation evaluates both:

    1. Quality Management System (QMS): Organisational structure, responsibilities, procedures, documentation.

    2. Technical Competence: Staff expertise, validated methods, calibrated equipment, and reliable results.

    3. Provides confidence to clinicians that results are valid and reliable.

    4. Microbiology testing is inherently variable due to biological systems. Accreditation ensures consistency and comparability of results.

  • Main Standards:

    • ISO 15189: Medical laboratories – Quality & competence requirements. Focuses on patient-centered testing.

    • ISO/IEC 17025: Testing & calibration laboratories – Covers technical competence; applicable for labs outside direct medical testing (e.g., water, food microbiology).

  • Benefits:

    • Credibility & Trust: Labs recognized nationally/internationally.

    • Patient Safety: Minimises diagnostic errors.

    • Compliance: Meets regulatory/clinical governance requirements.

    • Global Recognition: Results accepted worldwide through agreements (ILAC, EA, NABL, etc.).

Personnel Requirements

  • Qualification:

    • Staff must have formal training in microbiology (degree level or equivalent).

    • Supervisory roles require advanced knowledge and significant experience.

  • Competency & Training:

    • Skills: aseptic technique, colony counting, equipment handling, safety procedures.

    • Competence evaluated through tests, observation, and comparison against set criteria.

    • Ongoing monitoring ensures no skill degradation (esp. for infrequently used methods).

  • Documentation:

    • Competence records (training certificates, skill assessments).

    • Each staff member’s authorized scope of testing must be clearly defined.

  • Interpretation of Results:

    • Only authorized experts may add professional opinions or clinical interpretation to reports.

 

Laboratory Environment

  • Access: Restricted to authorized personnel. Prevents contamination and ensures biosafety.

  • Layout (“No-way-back principle”): Movement from clean → potentially contaminated → dirty areas; prevents cross-contamination.

  • Segregated areas include:

    • Sample receipt and storage.

    • Sample preparation (esp. high-risk materials).

    • Examination rooms & incubation.

    • Media preparation & sterilisation.

    • Reference organism storage.

    • Waste decontamination and disposal.

  • Environmental Monitoring:

    • Air & surface checks (settle plates, swabs).

    • DNA contamination monitoring in molecular labs (using No Template Controls).

  • Hygiene Measures:

    • Documented cleaning schedules.

    • Personal protective equipment (lab coats, gloves, masks, shoe covers).

    • Handwashing & glove policy to prevent organism spread.

    • Prohibition of personal items, plants, or unnecessary documents in work areas.

 

Validation & Verification of Methods

  • Validation: Confirms that a method works for its intended purpose.

    • Performed when using new/modified methods, or applying existing methods to new sample types.

    • Assessed through: specificity, sensitivity, limit of detection (LOD), limit of quantification (LOQ), reproducibility, and trueness.

  • Verification: Confirms that the laboratory can implement a validated method successfully in its own setting.

    • For example, a standard ISO method must be verified locally with spiked/reference samples.

  • Application:

    • Qualitative methods: detection of organisms (e.g., Salmonella not detected in 25 g).

    • Quantitative methods: enumeration (e.g., 3.2 × 10³ CFU/ml with 95% confidence).

 

Measurement Uncertainty

  • Quantitative Testing:

    • Accreditation requires labs to estimate uncertainty of measurement (UoM).

    • Based on repeatability, reproducibility, dilution error, incubation variation, etc.

    • Example: E. coli count = 2.4 × 10³ CFU/ml ± 0.5 × 10³ CFU/ml (95% confidence).

  • Qualitative Testing:

    • Not expressed numerically, but variability sources (false positives/negatives, reagent stability, analyst interpretation) must be identified and minimized.

  • Purpose:

    • Helps clinicians interpret results properly.

    • Supports comparability between laboratories internationally.

 

Equipment Management

  • Maintenance:

    • Regular cleaning, servicing, and sterilisation schedules.

    • Separate autoclaves for sterilisation vs. waste decontamination if possible.

  • Calibration & Performance Verification:

    • Must be traceable to national or international standards.

    • Examples:

      • Thermometers are calibrated annually.

      • Autoclaves validated with temperature mapping and spore testing.

      • Pipettes checked for volume accuracy.

  • Record Keeping:

    • Detailed logs of maintenance, calibration, and performance checks.

    • Records reviewed during audits.

 

Reagents & Culture Media

  • Reagents:

    • Suitability checked with positive & negative control organisms.

    • Stored under appropriate conditions.

  • In-House Prepared Media:

    • Tested for sterility, pH, ability to promote target organism growth, and ability to suppress non-target organisms.

  • Ready-to-Use Media:

    • Purchased from certified suppliers.

    • Accompanied by certificates of analysis.

    • The user laboratory performs acceptance checks.

  • Labelling:

    • Must include name, concentration, preparation date, expiry date, storage conditions, and responsible person.

 

Reference Materials & Cultures

  • Reference Materials (RM/CRM):

    • Used to calibrate equipment, validate methods, and monitor ongoing performance.

  • Reference Cultures:

    • Obtained from internationally recognised collections (e.g., ATCC, NCTC).

    • Stored as reference stocks (frozen/lyophilised).

    • Working cultures derived from reference stocks.

    • Avoid repeated sub-culturing to prevent genetic drift.

 

Sample Management

  • Sampling:

    • Performed aseptically by trained staff.

    • Conditions (time, place, environmental parameters) documented.

  • Handling & Identification:

    • On receipt, check sample condition (temperature, packaging, labelling).

    • Record receipt date/time and assign a unique ID.

  • Sub-Sampling:

    • Conducted according to ISO standards (ISO 6887, ISO 7218).

    • Designed to reduce error from uneven distribution of microorganisms.

  • Retention & Disposal:

    • Samples stored until results are issued.

    • Contaminated or hazardous samples must be decontaminated before disposal.

 

Waste Disposal

  • Methods:

    • Autoclaving, incineration, chemical disinfection.

  • Compliance:

    • Must follow national biosafety & environmental regulations.

  • Objective:

    • Protect staff, public, and environment from biohazards.

Quality Assurance

  • Internal Quality Control (IQC):

    • Daily/weekly checks with reference strains, spiked samples, duplicate testing.

    • Ensures test consistency and reliability.

  • External Quality Assessment (EQA):

    • Participation in proficiency testing (PT) schemes.

    • Required if available; otherwise, inter-lab comparison studies used.

  • Continuous Monitoring:

    • Internal audits, corrective and preventive actions (CAPA).

    • Management reviews for continual improvement.

 

Test Reports

  • Quantitative Results:

    • Expressed as CFU/ml or CFU/g.

    • Below reliable detection limits should be noted as “< detection limit”.

  • Qualitative Results:

    • Reported as “Detected / Not Detected” in specified volume/sample size.

  • Measurement Uncertainty:

    • If reported, must clearly state limitations (e.g., not accounting for organism distribution in the sample).

  • Clarity:

    • Reports must be clear, concise, and comply with ISO requirements.