Test Procedures

We’ve got a good sample, reliable reagents – now we need to make sure the way we perform the test is accurate, consistent, and follows the rules every single time. This is all about standardization and minimizing variables!

Think of it like baking: even with the best ingredients (sample & reagents), if you don’t follow the recipe (procedure) correctly – wrong oven temp, wrong mixing time – you won’t get a good cake. Same principle here, but the stakes are much higher!

Quality Assurance for test procedures ensures reliability and reproducibility, whoever is performing the test on whatever day. Here’s how we ensure that:

Standard Operating Procedures (SOPs): The Recipe Book

• The Foundation: Every test performed MUST have a detailed, written Standard Operating Procedure. This is the ultimate guide
• Content is Key: SOPs need to be comprehensive and include:
  • Test Principle: How does the test work?
  • Specimen Requirements: Acceptable sample types, collection, handling, storage, rejection criteria
  • Reagents & Equipment: List of all necessary materials, including preparation instructions if applicable
  • Quality Control: Required frequency, materials, expected results, corrective actions for failures
  • Step-by-Step Instructions: Clear, concise, unambiguous directions for performing the entire test from start to finish
  • Result Interpretation: Objective criteria for reading results (e.g., grading agglutination, gel patterns, solid phase patterns)
  • Reporting: How results are documented and reported (reference ranges, critical values, etc.)
  • Procedural Limitations: What can interfere with the test?
  • References: Supporting literature or manufacturer’s package inserts
• Accessibility & Updates: SOPs must be readily available to all staff performing the tests. They need to be reviewed regularly (usually annually) and updated whenever there’s a change in reagents, equipment, or procedure. Version control is essential!
• Following the SOP: Staff must follow the current SOP exactly as written. No shortcuts, no “this is how I’ve always done it.” Consistency is crucial

Personnel Training and Competency Assessment: The Skilled Chef

• Initial Training: Staff must be thoroughly trained on each procedure before performing it independently on patient samples. This includes understanding the principle, reading the SOP, hands-on practice, and demonstrating proficiency
• Competency Assessment: Regular assessment ensures staff maintain their skills and knowledge. This isn’t just about training; it’s proving they can still do it right. Methods include:
  • Direct Observation: Supervisor watches the technologist perform the test
  • Monitoring QC Records: Reviewing daily performance
  • Review of Test Results: Checking accuracy and interpretation over time
  • Testing Blind/Previously Tested Samples: Can they reproduce results?
  • Proficiency Testing (PT): Successful performance on external PT samples
• Frequency: Competency must be assessed after initial training, usually at 6 months, and then annually thereafter for each test the technologist performs
• Documentation: All training and competency assessments must be documented for each employee

Equipment and Environment: The Right Kitchen Tools

• Equipment Function Checks & Calibration: Equipment used in the procedure must be properly maintained and monitored (as covered partly under Reagent/Sample QA):
  • Centrifuges: Correct speed (RPM) and time are critical for proper cell button formation and resuspension. Calibrated regularly, timers checked
  • Incubators/Water Baths/Heat Blocks: Accurate temperature is vital for antigen-antibody reactions (especially 37°C for IgG). Monitored daily, calibrated regularly
  • Pipettes: Must deliver accurate volumes. Regularly calibrated and maintained
  • Timers: Must be accurate
  • Automated Systems: Require validation, routine maintenance, and built-in QC checks per manufacturer
• Work Environment: Adequate lighting for reading reactions, sufficient bench space, organized workflow to prevent errors

Test Performance - Adherence to Critical Steps

• Following the SOP: Worth repeating!
• Correct Sample/Reagent Addition: Using the right volumes, adding reagents in the correct sequence
• Proper Mixing: Ensuring adequate mixing of samples/reagents without causing hemolysis
• Incubation Times & Temperatures: Adhering precisely to the times and temperatures specified in the SOP is critical for allowing reactions to reach completion or avoiding unwanted reactions
• Washing Steps (for AHG tests): Performed correctly and thoroughly to remove unbound globulins – essential to prevent false negatives. Correct saline volume, number of washes, technique for decanting
• Centrifugation: Using the correct time and speed for the specific procedure/equipment. Too much/too little affects reading
• Reading/Observation Technique: Using a consistent, standardized technique for resuspending cell buttons or observing reactions in gel/solid phase. Using appropriate optical aids if needed. Good lighting is essential

Result Interpretation and Reporting

• Objective Criteria: Using the grading system defined in the SOP consistently (e.g., 0-4+ for agglutination, gel patterns). Avoiding subjective bias
• Controls: Ensuring internal procedural controls (like Rh control, autocontrol, Check Cells for negative AHG tests) give the expected results before accepting patient results
• Correlation: Checking if results make sense in the context of other tests (e.g., forward vs. reverse type, screen vs. crossmatch)
• Accurate Recording & Reporting: Transcribing results accurately, reporting using standard terminology, and following procedures for critical value reporting

Troubleshooting and Corrective Action

• Recognizing Errors: Identifying unexpected or discrepant results, QC failures, or procedural deviations
• Following Protocols: Having clear procedures for investigating errors or unexpected results
• Corrective Action: Implementing steps to fix the immediate problem
• Preventive Action: Analyzing the root cause to prevent recurrence
• Documentation: Recording all troubleshooting and corrective actions taken

Proficiency Testing (PT) / External Quality Assessment (EQA)

• External Check: Regularly testing “blind” samples from an external agency (like CAP)
• Purpose: Assesses the laboratory’s overall performance for a specific test procedure compared to peer labs. Confirms the entire system (personnel, reagents, equipment, procedure) is working correctly
• Process: PT samples must be integrated into the routine workflow and tested by personnel who normally perform the test, using the lab’s standard procedures

Key Terms

• Standard Operating Procedure (SOP): Detailed, written instructions for performing a specific test or task, ensuring consistency and standardization
• Competency Assessment: The evaluation of an individual’s ability to perform a test or task correctly and according to procedure, conducted at regular intervals
• Calibration: The process of adjusting or verifying the accuracy of measuring equipment (e.g., centrifuges, pipettes, thermometers) against known standards
• Critical Steps: Specific points within a test procedure that must be performed precisely (e.g., incubation time/temp, washing, centrifugation) to ensure accurate results
• Result Interpretation: The process of evaluating the outcome of a test based on objective criteria defined in the SOP (e.g., grading agglutination)
• Proficiency Testing (PT) / External Quality Assessment (EQA): A program where laboratories test unknown samples provided by an external agency to assess their performance against peer laboratories
• Corrective Action: Steps taken to resolve an identified problem or error (e.g., QC failure, procedural deviation)
• Preventive Action: Steps taken to eliminate the cause of potential problems to prevent them from occurring
• Version Control: A system for managing changes to documents like SOPs, ensuring that only the current, approved version is in use