Evaluation of Quality Control in Clinical Chemistry Using Sigma Metrics

IntroductionSix sigma improves the quality of outputs by analyzing and abolishing the source of defectsand reducing variability in the manufacturing industry. It can be used as a self -assessmenttool for laboratories when making their quality control frequency and strategy. Clinicallaboratories tests with low sigma values (< 3σ) indicate that the analytical quality of the labneeds to be improved.AimThe aim of the study was to evaluate clinical chemistry laboratory performance using sixsigma metrics to improve quality.Materials and methodsFive parameters from renal and liver function tests were studied over a period of 6 months(Dec 2016-May2017). Data from IQC and EQA participation was used. The analytes wereplasma creatinine, aspartate transaminase(AST), alanine transaminase(ALT), total serumprotein, total and direct bilirubin.Sigma metrics was calculated using total allowable error as per CLIA recommendations. Biaswas calculated from HUQAS EQA participation while coefficient of variation was calculatedfrom IQC data collected during the above mentioned months.Results.Clinical chemistry had sigma metrics below 3, the highest sigma value was 2.01 while thelowest sigma value was 0.85.ConclusionClinical chemistry analytes had sigma levels less than 3, method performance improvementwith stringent internal quality control and correct setting of control limits need to be applied.Application of sigma metrics in addition to daily internal quality control can identifyanalytical deficits and improvement in clinical laboratories