Evaluation of a new automated system for the determination of ck‐mb isoforms

Abstract We evaluated a new analyzer (Cardio REP) specifically designed for cardiac CK‐MB isoenzyme and isoforms activity, with a performance time of 24 minutes. Ten AMI patients, with times elapsed between the onset of chest pain and admission to hospital ranging from 30 minutes to 4 hours, were monitored every 3–4 hours until the 16th hour of hospitalization. In each serum sample, in addition to total CK‐MB and CK‐MB isoforms measured by the Cardio REP analyzer, we also assayed total CK activity, CK‐MB activity by immunoinhibition method, CK‐MB mass concentration, CK‐MB isoforms by REP method, troponin T, and myoglobin. The precision study demonstrated acceptable within assay and between assay CVs% for total CK‐MB (8.1 and 10.4), MB 1 (9.1 and 14.2), and MB 2 (9.1 and 8.2) isoforms. The method was found to be linear up to 371 U/L for MB 2 isoform fraction and up to 516 U/L for total CK‐MB. Results for CK‐MB obtained with the Cardio REP correlated well with those for CK‐MB activity obtained with the immunoinhibition method (r = 0.869) and those of CK‐MB mass concentration (r = 0.923). The sensitivity of the Cardio REP CK isoforms method was found to be greater than that of the REP CK isoforms method. Time to first increased value of MB 2 /MB 1 ratio and MB 2 isoform was earlier in comparison to that for CK‐MB mass concentrations and similar to that for myoglobin, a marker that, however, lacks specificity. The diagnostic efficiency of CK‐MB isoforms and the availability of a real‐time, fully automated method for their measurement suggest the utilization of this biochemical marker in emergency for the early diagnosis of AMI.