A method for the estimation of peak serum LDH activity based on a single post-peak level after acute myocardial infarction.

A new method was developed to estimate the peak serum lactic dehydrogenase (LDH) value in patients with acute myocardial infarction from a single determination of serum LDH activity in the post-peak period (3rd to 5th day after the onset of infarction) using nomogram method based on the monoexponential decay of serum LDH with a decay constant of 0.012 hours-1. To develop this nomogram, the serial changes in serum LDH activities were studied in 30 patients with acute myocardial infarction admitted to the coronary care unit within the pre-peak period. The mean errors in estimation from data of the 3rd, 4th, or 5th day after the onset were acceptably small, 10.5 +/- 1.9%, 14.5 +/- 2.8%, and 15.9 +/- 3.3%, respectively. Furthermore, a correction formula was obtained to improve the accuracy of estimation, since the peak values were underestimated in patients with actual peak values less than 300 units and overestimated in the case of more than 500 units. Estimation in 9 patients of an external sample group confirmed that this nomogram is useful clinically with mean errors of less than 25%.