Fifth Generation Quality Control of Immunoassay Parameters by Six Sigma Value.

Objective: To determine the sigma value of immunoassay parameters which are within the 2Z score on external quality control (EQC).

Study Design: A cross-sectional study. Place and Duration of the Study: Department of Chemical Pathology and Endocrinology (AFIP),non-ability ity consecutive  from June to November 2022.

Methodology: Ten immunoassay parameters were selected on the basis of the internal quality control (IQC) and external quality control (EQC) programs. The Clinical Laboratory Improvement Amendments (CLIA) is used for Total Allowable Error (TEa). Sigma value was calculated from coefficient of variation (CV) and bias, which was determined by IQC and EQC, observed for 6 subsequent months. If the sigma values are ≥6, between 3 and 5, and <3, they are classified as good, acceptable or unacceptable, respectively.

Results: T4, prolactin, Vitamin B12 at >3 ó at IQC level 1. TSH, T3, T4, and Vitamin B12 showed that on level 2 IQC at >3 ó T3, Vitamin D at 4-5 ó level, Prolactin, FSH, and LH at 6 ó level in level 2 IQC. In the EQC program, the sigma level calculated for ten assays found that almost all parameters were at sigma >3 ó level except TSH which was at 5.8 ϭ level during June to August 2022. From September to November 2022, all parameters at >3 ó level except for TSH, growth hormone, FSH, LH, and Vitamin b12 which showed at 4.4 ó level.

Conclusion: Most of the immunoassay parameters show good performance in the EQC program and at both levels of IQC level with sigma value 4-5.

Key Words: Bias, Six sigma, Key performance indicators, External quality control.