A new method for reporting the sources of abnormal activities of lactate dehydrogenase in serum

We have developed and tested a new method to increase the diagnostic usefulness of measurements of lactate dehydrogenase (LDH; EC 1.1.1.27) isoenzymes. The method estimates the separate contributions from enzymatically distinct organ clusters (e.g., heart/kidney/erythrocyte, liver/muscle, lung) to the total activity of LDH in serum. To test this method, we monitored serum LDH isoenzymes over the entire hospital course of 73 patients admitted to the intensive-care unit with chest pain, myocardial infarction, or serious hemodynamic disturbances. The organ-specific estimates provided useful information beyond measurements of the original isoenzymes. The sensitivity and specificity of this new method in detecting acute myocardial infarction, as well as concomitant disorders involving the liver or lung, are significantly greater than those of other diagnostic indices or pathologists' judgments. Serial plots of the organ-specific estimates may provide additional insight into evolving pathophysiological processes.