Clinical significance of creatine kinase isoform assay by a new reagent based on immunoinhibition method

: Clinical significance of creatine kinase (CK) isoform assay by a new diagnostic reagent based on immunoinhibition method was evaluated. In the method, a monoclonal antibody (CKM-G 01), which inhibits MM3 but not MM1 isoform, was used. Serial serum samples from 143 acute myocardial infarction (AMI) patients were examined in hospitals. Isoform ratio (I.R.: defined as follows; inhibited CK activity/uninhibited CK activity) increased most rapidly (whose peak appeared 8.5 h after onset of AMI), compared with total CK (18.3 h) and CK-MB (16.1 h). In 61 patient samples collected within 4 h from onset, I.R. in 25 samples (41%) exceeded reference interval, whereas total CK in only 17 samples (28%) did it. Reference interval of the I.R. was 0.42 +/- 0.33 (mean +/- SD) in 1,246 normal subjects. These results show that the assay of CK isoforms by the reagents based on immunoinhibition method is useful for earlier detection of AMI.