Six-sigma calculation for serum protein markers according to 2025 CLI ˙A total allowable error criteria

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Yıldırım Şık B., Öztaş B.

Febs 2025, İstanbul, Türkiye, 5 - 09 Temmuz 2025, ss.330, (Özet Bildiri)

Özet

Six-sigma methodology is one of the quality measurement methods used to evaluate laboratory performance. The sigmametric method evaluates internal (IQC) and external quality control (EQC) processes together. Serum proteins, used as biomarkers play critical roles in various biological processes. In this study, we aimed to evaluate the analytical performance of serum protein markers C3, C4, IgG, IgA, IgM by sigmametric method according to the 2025 CLIA Acceptance Limits. The study was conducted Kocaeli University Faculty of Medicine Hospital Central Laboratory, carried out on the Roche Cobas 8000c702 (Roche, Basel, Switzerland) biochemistry auto-analyzer for December 2024 and January 2025. IQC (Cobas PreciControl ClinChem Multi 1 and 2) data used for calculating coefficient of variation (%CV). EQC data obtained from the External Quality Assurance Services (EQAS) and used in %bias calculation. On the sigma scale, sigma values are≤3 low; 3–6 acceptable;≥6 good. According to December 2024 data, Six-sigma values was calculated as for level 1 and 2 IQC materials, respectively C3 (4.23-3.52); C4 (10.93-7.13); IgG (10.23-11.56); IgM (6.13-4.59); IgA (10.99-13.16). According to January 2025 data was calculated as, level 1 and 2, respectively C3 (5.89-7.16); C4 (3.91 5.9); Ig G (6.93-9.66); IgM (2.94-3.8); IgA (5.02-5.23). When the December and January data were examined, IgA showed the highest performance. IgM (Level 1) showed the lowest performance and sigmametric evaluation was below 3 sigma. According to our results, it is seen that the internal and external quality control results evaluation of IgM in both December and January are within the normal range however, the six-sigma performance was found to be low. Different analyses and  methods should be used to determine the variables that cause low sigma levels, and more detailed evaluations and arrangements should be made in order to increase the analytical performance of this test.