Principles in Laboratory Quality Assurance and Errors
- Ensuring quality in laboratory processes is a collective responsibility, including clinicians, laboratory personnel, and those collecting blood samples.
- Key Principles include precision, accuracy, sensitivity, and specificity. Precision refers to the consistency of test results, while accuracy is the conformity of results to a recognised standard. Sensitivity is the ability to identify true positives, and specificity is the capacity to identify true negatives.
Causes of Sample Rejection and Factors Causing Sample Errors
- Pre-analytical errors occur before the sample reaches the laboratory, often resulting from improper collection, incorrect forms, and patient misidentification. Although these are the most frequent errors, they are generally easier to rectify.
- Analytical errors occur during laboratory analysis and can arise from equipment malfunction, operator error, or issues with reagents. Such errors can be minimised through regular maintenance, calibration, and thorough training of laboratory staff.
- Post-analytical errors occur after results have been issued and include data misinterpretation, data entry errors, and transmission errors. Ensuring accurate post-analytical processes is crucial for effective clinical decision-making.
- Patient-specific factors, including medical history, medications, and physiological conditions like pseudothrombocytopenia, lipaemia, icteric samples, and red cell agglutination can influence errors. Administrative factors, such as patient identification errors, incorrect forms, and mislabeling, also contribute. The collection process itself, including technique, tube selection, and proper handling, is another critical factor. Post-collection handling, including storage temperature and transport conditions, is vital.
- To reduce errors, avoid haemolysis by not drawing blood from intravenous (IV) cannulas, avoiding vigorous mixing, and using the correct needle size. Prevent clot formation by adequately mixing blood with anticoagulants and using vacutainer systems. Avoid contamination by not drawing blood from arms with IV infusions and discarding initial blood from central venous devices. Ensure correct labelling and avoid agitation during transport. Process samples promptly, ideally within 6 to 24 hours.
- Perform regular checks for equipment expiry and implement correct collection techniques to avoid haemolysis, clotting, and contamination. Ensure proper storage and timely processing of samples. This is especially critical for certain acute leukaemias and cold agglutinin disease.