Characteristics of an albumin cobalt binding test for assessment of acute coronary syndrome patients: A multicenter study

Background: The ability of the N-terminal region of human albumin to bind c obalt is diminished by myocardial ischemia. The characteristics of an assay based on albumin cobalt binding were assessed in suspected acute coronary syndrome patients and in a control reference population. The ability of the Albumin Cobalt Binding (ACB(TM)) Test measurement at presentation to predi ct troponin-positive or -negative results 6-24 h later was also examined. Methods: We enrolled 256 acute coronary syndrome patients at four medical c enters. Blood specimens were collected at presentation and then 6-24 h late r. The dichotomous decision limit and performance characteristics of the AC B Test for predicting troponin-positive or -negative status 6 h-24 h later were determined using ROC curve analysis. Results for 32 patients could not be used because the time of onset of ischemia appeared to have been >3 h b efore presentation or was uncertain. The reference interval was determined by parametric analysis to estimate the upper 95th percentile of a reference population (n = 109) of ostensibly healthy individuals. Results: Increased cTnI was found in 35 of 224 patients. The ROC curve area for the ACB Test was 0.78 [95% confidence interval (CI), 0.70-0.86]. At th e optimum decision point of 75 units/mL, the sensitivity and specificity of the ACB Test were 83% (95% CI, 66-93%) and 69% (95% CI, 62-76%). The negat ive predictive value was 96% (95% CI, 91-98%), and the positive predictive value was 33% (95% CI, 24-44%). The within-run CV of the ACB Test was 7.3%. Results for the reference population were normally distributed; the one-si ded parametric 95th percentile was 80.2 units/mL. Conclusions: This exploratory study suggests that the ACB Test has high neg ative predictive value and sensitivity in the presentation sample for predi cting troponin-negative or -positive results 6-24 h later. (C) 2001 America n Association for Clinical Chemistry.