Questions
2 questions per theory paper
Difficulty
Medium
Importance
Core topic for BMLT/MBBS practical vivas
Overview
Quality Control (QC) in a biochemistry laboratory is a systematic process designed to ensure the accuracy, precision, and reliability of analytical test results. It is a fundamental component of laboratory management that minimizes diagnostic errors and patient risk, making it a recurring focus in medical and paramedical university examinations.
Internal Quality Control (IQC)
IQC is an ongoing, real-time procedure performed daily within the laboratory to monitor the performance of analytical methods. It involves running control samples of known concentrations alongside patient specimens to verify that the results are within acceptable limits.
- Uses commercially available control sera
- Monitors precision (reproducibility) of assays
- Levey-Jennings charts are standard tools for plotting data
- Westgard rules are applied to identify systematic or random errors
External Quality Assurance (EQA)
EQA, or Proficiency Testing, involves an external agency sending blinded samples to the laboratory to compare its performance against other laboratories. It is crucial for identifying long-term bias and maintaining standardized clinical performance across regional or national health networks.
- Evaluated via Z-score or standard deviation index
- Conducted periodically (monthly or quarterly)
- Objective assessment of laboratory accuracy
- Blind testing prevents operator bias
Instrument Calibration Basics
Calibration is the process of defining the relationship between the analytical response of an instrument and the actual concentration of the analyte. Regular calibration ensures the measurement system remains traceable to international standards or reference materials.
- Involves using calibrators with assigned values
- Required after major maintenance or reagent lot changes
- Ensures accuracy (trueness) of measurements
- Establishes the linear range of the analytical method
Formula Sheet
Coefficient of Variation (CV) = (Standard Deviation / Mean) * 100
Z-score = (Laboratory Result - Peer Mean) / Peer Standard Deviation
Exam Tip
Always link the importance of QC to patient safety and clinical decision-making; examiners prioritize the ability to detect systematic versus random errors.
Common Mistakes
- Confusing the purpose of IQC (precision) with EQA (accuracy and inter-lab comparison).
- Failing to distinguish between a control (known range) and a calibrator (known target value).
- Incorrectly interpreting Westgard rules when plotting Levey-Jennings charts.
More Revision Notes
Ready to test yourself?
Play topic-wise Quality Control in Biochemistry Lab questions in Aspirant Arcade — gamified MCQ practice.
Download Free