Utility of Capability Index and Quality Goal Index Ratio as Determinants of Quality Adherence in a Clinical Biochemistry Laboratory

Abstract

Background and Objective: The measurement of the coefficient of variation (CV%) and bias has been used to check the precision and accuracy of laboratory-generated data. Indices like the capability index (Cp and Cpk) and the quality goal index ratio (QGI) take into account both CV and bias in order to categorize the results of various parameters, allowing for necessary actions to improve the outcomes of poorly performing parameters. Materials and Methods: This is a retrospective study, and data required for the study were extracted between January 2024 and June 2024 from a tertiary care government hospital in Delhi. The Cp, Cpk, and QGI were calculated, and six-month averages of these indices were taken to categorize the parameters. Results: For level 1 of internal quality control (IQC), the Cp indicated that sodium, chloride, urea, and low-density lipoprotein (LDL) performed marginally well, while potassium performed poorly. Meanwhile, the Cpk showed poor performance for sodium, potassium, chloride, urea, LDL, amylase, and lactate dehydrogenase (LDH). Sodium, potassium, chloride, urea, and creatinine had a QGI of <0.8, indicating that the bias was due to imprecision, while LDL had a QGI of >1.2, indicating that the bias was due to inaccuracy. For level 2 of IQC, Cp showed that sodium, chloride, LDH, and LDL were in the marginal range, and potassium performed poorly, while Cpk indicated poor performance for sodium, potassium, chloride, urea, protein, LDL, and LDH. Sodium, potassium, chloride, urea, and protein had a QGI of <0.8, indicating that the bias was due to imprecision, while the QGI of LDL was between 0.8 and 1.2, indicating that the bias was due to both inaccuracy and imprecision. Conclusion: This study shows that Cp, Cpk, and QGI can be used to assess the analytical performance of a clinical chemistry laboratory and to implement measures for improving quality assurance.