Application of sigma metrics for the assessment of quality control in clinical chemistry laboratory in Ghana: A pilot study

Abstract

Background:Sigma metrics provide a uniquely defined scale with which we can assess the performance of a laboratory. The objective of this study was to assess the internal quality control (QC) in the clinical chemistry laboratory of the University of Cape Cost Hospital (UCC) using the six sigma metrics application.Materials and Methods:We used commercial control serum [normal (L1) and pathological (L2)] for validation of quality control. Metabolites (glucose, urea, and creatinine), lipids [triglycerides (TG), total cholesterol, high-density lipoprotein cholesterol (HDL-C)], enzymes [alkaline phosphatase (ALP), alanine aminotransferase (AST)], electrolytes (sodium, potassium, chloride) and total protein were assessed. Between-day imprecision (CVs), inaccuracy (Bias) and sigma values were calculated for each control level.Results:Apart from sodium (2.40%, 3.83%), chloride (2.52% and 2.51%) for both L1 and L2 respectively, and glucose (4.82%), cholesterol (4.86%) for L2, CVs for all other parameters (both L1 and L2) were >5%. Four parameters (HDL-C, urea, creatinine and potassium) achieved sigma levels >1 for both controls. Chloride and sodium achieved sigma levels >1 for L1 but <1 for L2. In contrast, cholesterol, total protein and AST achieved sigma levels <1 for L1 but >1 for L2. Glucose and ALP achieved a sigma level >1 for both control levels whereas TG achieved a sigma level >2 for both control levels.Conclusion:Unsatisfactory sigma levels (<3) where achieved for all parameters using both control levels, this shows instability and low consistency of results. There is the need for detailed assessment of the analytical procedures and the strengthening of the laboratory control systems in order to achieve effective six sigma levels for the laboratory.

Application of Sigma Metrics Analysis for the Assessment and Modification of Quality Control Program in the Clinical Chemistry Laboratory of a Tertiary Care Hospital

“…Sigma metric analysis is used to measure the performance of a process [8]. In clinical laboratories, assessment of the performance can be done separately for preanlytical, post analytical and analytical phases or as overall laboratory process system.…”

Quality specifications of routine clinical chemistry methods based on sigma metrics in performance evaluation

“…In many Chinese clinical laboratories, the Westgard multiplication rules (1 3s , 2 2s , R 4s , 4 1s , 10 x ) have been widely used in clinical chemistry. In this method, there may be more false rejection, waste of quality control materials and prolonged test awaiting time (TAT), whereas the sigma metrics approach allows a laboratory to take a broader view of the data, joining estimates of bias and imprecision into a practical judgment on the clinical usefulness of the method's quality control criteria . Thus, it is useful and simple to access and choose optimal internal quality control criteria based on sigma metrics.…”

Analytical performance evaluation of a high‐volume hematology laboratory utilizing sigma metrics as standard of excellence

“…In laboratory settings, the former purpose is fulfilled by total allowable error (TEa) and bias whereas coefficient of variation (CV) can be utilized for the later. Several studies have addressed analytical performance of biochemical parameters on sigma scale . Literature review revealed a lack of studies assessing the analytical performance of hematological parameters on sigma scale.…”