Quality Control Planning in Clinical HematologyLaboratory by Using Sigma Metric and OPSpecs Chart

Sumonta Supol


The use of optimized QC procedure has proven its values for controlling analytical quality in clinical laboratory. The aim of this study was to apply Six sigma concept for more efficient quality control planning in Clinical Hematology Laboratory, Medical Technology Department of Nakhon Nayok Hospital. Sigma metric of hematological testings was determined and the analytical performance was evaluated. Control materials for four parameters including RBC count (RBC), WBC count (WBC), platelet count (PLT), and hemoglobin (HBG) at three levels (low, normal, high) were determined on autoanalyzer, Coulter Hmx. Control materials (two levels; normal and abnormal) of prothrombin time (PT) and partial thromboplastin time (PTT) were determined by autoanalyzer, Sysmex CA 600. When considered from Sigma values, analytical performance of normal and high level controls for RBC, PLT and HBG were excellent (Sigma > 6) while that of WBC was also very good (Sigma > 5). However, performance of low level control for WBC had Sigma < 4 thus its quality control procedure must be more stringent than the others. Performance of PT and PTT were also evaluated from their Sigma values, and the performance of PT at normal and abnormal levels was satisfactory (Sigma > 4) while PTT had excellent performance at normal level and very good at abnormal level. The difference in analytical performance of each parameter indicates varying degrees of attention in quality control procedure. Sigma values and OPSpecs chart were taken into consideration to select the control rule, number of control measurement and analytical run. In conclusion, the use of optimized QC procedures from QC planning tools can lead to more efficient QC performance.

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