Hematology Laboratory Operations, Quality, and Instrumentation
Laboratory operations, quality, and instrumentation
Quality in hematology spans preanalytical, analytical, and postanalytical phases. Preanalytical errors include wrong anticoagulant, underfilling citrate tubes, EDTA-induced platelet clumping, hemolysis, lipemia, and delayed processing. Correct specimen handling-fill lines, mixing, stability, and rejection criteria-prevents most errors. Analytical quality uses calibration, reagent validation, and statistical QC. Levey-Jennings charts and Westgard rules detect random and systematic error: 1:2s warning, 1:3s, 2:2s, R:4s, 4:1s, and 10:x rejection rules. Proficiency testing, linearity, reference interval verification, delta checks, and critical value reporting are required by accreditation programs. Automated analyzers use impedance, light scatter, flow cytometry, and fluorescence; WBC counts must be corrected for nucleated red cells, and platelet counts for clumping or large platelets. Coagulation analyzers use mechanical, turbidimetric, or chromogenic methods. Point-of-care testing requires the same QC rigor.
Traps: 1:2s is a warning, not rejection. R:4s indicates within-run random error; 2:2s across runs suggests systematic error. A normal result does not exclude a preanalytical problem. Carryover and dead volume affect counts. Hemolysis falsely raises potassium and LDH but not always hemoglobin.
Worked example: two QC levels differ by 4.5 SD in the same run-apply the R:4s rule and reject the run.