Lactate dehydrogenase isoenzyme levels in collagen disease.

Serum lactate dehydrogenase (LDH) isoenzymes were determined in 27 patients with collagen disease and 88 normal subjects. The mean value for LDH-3 isoenzyme was 20.4 +/- 3% in normal controls, 31.47 +/- 8.9% in patients with collagen disease who showed activity of the disease, and 20 +/- 3.74% in patients in complete remission. Six patients who had positive rheumatoid factor showed higher LDH-3 levels. There was also some correlation between the activity of the disease and serum LDH-3 level in patients with connective tissue disorders.