Evaluation of the Analytical Performance of a High-Precision Immunoassay for the Creatine Kinase-MB Isoenzyme

Background Creatine kinase-MB isoenzyme (CK-MB) is an important biomarker for diagnosing myocardial injury. Although cardiac troponin is widely used as the primary biomarker for myocardial infarction, CK-MB measurement remains clinically relevant due to its shorter half-life and utility in detecting reinfarction and estimating infarct size. Here, we established and evaluated a fully automated chemiluminescent enzyme immunoassay (CLEIA; Lumipulse Presto CK-MB) for the LUMIPULSE L2400 analyzer. The primary objective was to assess its analytical performance, and the secondary objective was to explore its potential clinical utility as a cardiac biomarker in patients with diabetes. Methods Analytical performance was assessed according to Clinical and Laboratory Standards Institute (CLSI) guidelines, including evaluations of sensitivity, linearity, dilution recovery, precision (repeatability, between-run, between-day, and total), and interference/cross-reactivity. Method comparisons were conducted using a panel of 95 CK-MB-positive serum samples against existing CLEIAs, chemiluminescent immunoassays (CLIA), immunoturbidimetry assays, and a CK-MB activity assay. Pearson correlation and Passing-Bablok regression were used to assess agreement. Discrepant samples were subjected to isoenzyme analysis. An exploratory clinical study measured CK-MB concentrations, as well as multiple other cardiac biomarkers, using banked serum samples from 120 diabetic patients grouped according to cardiovascular disease history and 92 diabetic patients grouped according to hypoglycemic treatment risk. Results The assay demonstrated high analytical sensitivity (limit of detection: 0.039 ng/mL; limit of quantification: 0.047 ng/mL), excellent linearity over a range of 0.1-349.0 ng/mL, and robust precision (coefficient of variations (CVs) < 3.5%). Strong correlations were observed with existing CLEIA (r = 1.00, 95% CI: 0.995-0.999), CLIA (r = 0.99, 95% CI: 0.988-0.994), and immunoturbidimetry (r = 1.00, 95% CI: 0.992-0.997) assays for CK-MB quantification. All discordant results were resolved by isoenzyme analysis. CK-MB levels were significantly higher in diabetic patients with a history of myocardial infarction compared with those without cardiovascular disease (p < 0.001). Conclusions The CK-MB assay demonstrated excellent sensitivity, precision, and strong correlation with conventional procedures. Isoenzyme analysis provided insights into discrepancies observed with activity-based measurements. Exploratory analysis of diabetic patient samples revealed trends related to cardiovascular history. These findings support the potential utility of this assay in both clinical diagnostics and research settings and encourage further multicentric studies to confirm its clinical usefulness, including exploratory observations suggesting broader applicability in populations at elevated risk for cardiac disease.