Assessing inter-method agreement for six enzymatic activities via Pooled Human Sera

INTRODUCTION: The International Federation of Clinical Chemistry and Laboratory Medicine created a reference measurement system for enzymatic activities measurements. Aim of this study is the evaluation of the harmonization of six enzymatic activities across major vendors.METHODS: Fifteen human serum pools were measured in triplicate across major vendors (Roche, Abbott, Beckman, Siemens, Werfen and Ortho) in 10 clinical laboratories. The correlation and the bias among vendors for alkaline phosphatase (ALP), alanine and aspartate aminotransferase (ALT, AST), cholinesterase (CHE), creatin kinase (CK), lactate dehydrogenase (LDH) are analyzed.RESULTS: For ALP the Beckman systems provided clearly lower results: -15% from the overall mean (OM), all the others provided results from ~ -5% to ~ +10% from OM. For ALT and AST the pyridoxal phosphate activated methods provided higher results; including all methods the differences for ALT spanned from ±30% at lower concentrations to ±20% at higher concentrations; for AST the dispersion was slightly lower: +15% to -25% at lower and ±10% at higher concentrations. CHE showed the largest dispersion of results: from -30% to +40% from OM. For CK Ortho produced lower results (~ -15%) while the others gave results from ±10% to ±6% from OM. For LDH Werfen used the pyruvate-lactate optimization producing results almost double than the other systems that adopted the IFCC optimization, with dispersions from ±8% to ±5% from OM.DISCUSSION: The findings highlight the need for broader adoption of standardized methods, improved manufacturer practices, and enhanced external quality assessment to ensure reliable and comparable enzyme measurements in clinical settings.