ANALYTICAL EVALUATION AND COMPARISON OF DUPONT ACA(R) LACTATE DEHYDROGENASE-1 (LD1) ISOENZYME ASSAY DIAGNOSTIC EFFICIENCY FOR ACUTE MYOCARDIAL-INFARCTION DETECTION WITH OTHER LD1 METHODS AND ACA(R) CK-MB - A 2-SITE STUDY

The purpose of this study was to examine the analtyical characteristic s of a rapid new assay for lactate dehydrogenase 1 (LD1) isoenzyme on the Dupont aca(R) analyzer and the diagnostic efficiency of LD1 for de tection of acute myocardial infarction (AMI) when used alone and with creatine kinase MB (CKMB). Total aca LD1 assay precision, with percent coefficients of variation (%CVs) of less than 3.2% from 56 U/L to 469 U/L LD1, across fifty assay days was excellent. Linearity was confirm ed from 0 to 332 U/L and no detectable calibration drift was noted fro m 5 to 489 U/L over a ninety-day period. The aca LD1 results compared well with Roche Isomune-LD1, Abbott Spectrum A-Gent, Helena electropho resis, and Beckman electrophoresis LD1 methods, giving r's from 0.987 to 0.994, slopes from 0.94 to 1.65, and y-intercepts from -2.95 to 6.9 4 U/L. Examination of 450 ambulatory subjects, about equally distribut ed by sex, yielded a 43 +/- 14 U/L aca LD1 patient reference interval. Serum samples from 159 consecutive patients at the University of Tenn essee Memorial Hospital and 96 patients at Allentown Hospital, submitt ed for AMI detection assistance, were assayed in a single-blind study for LD1 and ion-exchange CKMB by Dupont aca methods, which provide aut omated results in ten minutes whenever needed. The aca LD1 assay yield ed a clinical sensitivity of 89% and specificity of 95% for AMI with a decision threshold of 120 U/L. The diagnostic efficiency of the aca L D1 assay was 94% at 120 U/L, which equaled or exceeded that of the thr ee comparative LD1 methods. The predictive value of positive (PV+) and negative (PV-) results on the first sample collected were 80% and 85% for aca LD1, 65% and 90% for aca ion-exchange CKMB, and 83% and 90% w hen both tests were combined. Significantly, the PV+ and PV- results w hen two or more samples were assayed was improved to 88% and 95% for a ca LD1, relatively constant at 65% and 97% for aca ion-exchange CKMB, and dramatically improved to 95% and 100% when both CKMB and LD1 tests were combined. The results from these two medical centers show that t he aca LD1 assay provides useful clinical information for AMI diagnosi s when employed alone or in combination with aca CKMB. These results a lso suggest that LD1 should be included in biochemical evaluations for AMI to attain optimal predictive values of results.