Determination of Six Sigma Metric in Control of Enzymes Determination in Human Serum.

Background: Clinical Chemistry is the backbone of medical treatment, diagnostics, and prevention. The laborato-ries are trying to improve the quality and to reduce diagnostic errors and processing time and safeguard trace-ability of all laboratory procedures to ensure patient safety. Six sigma belongs to statistical quality control and provides a new methodology for measuring and improving process performance in laboratory.

Methods: Activities of AST, ALT, CK, LDH, Amy, and γ-GT were determined by standard kinetic methods on a Vitros 5600 biochemistry analyzer. Two daily quality controls (Verifier I and Verifier II) were run over 60 days. Total percent CV was calculated from routine daily QC. Between-instrument bias was also calculated from daily QC.

Results: The calculated sigma metrics for AST were 6.9 and 3.8; for ALT 9.3 and 5.6; for CK 6.6 and 5.3; LDH 5.2 and 5.2; for γ-GT 4.9 and 2.7; and for amylase 8.7 and 7.1. Analytical performance for AST, ALT, CK, LDH, and Amylase is world class. On the other hand, γ-GT analytical performance is poor.

Conclusions: Six Sigma benefits from earlier quality management approaches that creates new challenges for medical laboratories.