Lactate dehydrogenase isoenzyme 1 as determined by inhibition with 1,6-hexanediol and by two other methods in patients with myocardial infarction or cardiac-bypass surgery.

In this assay for lactate dehydrogenase (EC 1.1.1.27) isoenzyme 1 (LD-1), 1,6-hexanediol is added to serum after total LD has been measured. After incubation for 5 min the total LD remaining is determined. Samples from patients who had a myocardial infarction or who had undergone bypass surgery were assayed simultaneously by the 1,6-hexanediol method, the Roche "Isomune LD," and by electrophoresis on agarose gel. For 101 analyses of sera from bypass patients, correlations were high for results by the inhibitor method and electrophoresis (r = 0.96), by Roche Isomune and the inhibitor method (r = 0.96), and by the Roche method and electrophoresis (r = 0.97). In general, values for total LD were quite comparable by the three methods, but results by the inhibitor method seemed slightly higher and showed greater variability (CV) than those by the electrophoretic method. The assay is simple--requiring one reagent addition and a short incubation--and inexpensive: LD-1 can currently be determined for less than 1 over the cost of determining total LD.