Serum lactate dehydrogenase-3 isoenzyme in chronic granulocytic leukemia.

Abstract

Abnormal levels of serum lactate dehydrogenase-3 (LD-3) activity were observed in 92% of patients (35 of 38) with active chronic granulocytic leukemia (CGL), in 40% of patients (4 of 10) in partial remission, and in 13% of patients (1 of 8) in complete remission. In evaluating the electrophoretic LD isoenzyme patterns of these patients, three criteria were used. In criterion-1 elevations, the LD-3/total LD ratio, expressed as a fraction of serum total LD, and LD-3 value, expressed in absolute units, were greater than the upper limit of the reference range. In criterion-2 elevations, only the LD-3/total LD ratio was greater than the upper limit of the reference range. In criterion-3 elevations, only the absolute LD-3 activity exceeded the upper limit of the reference range, and these specimens showed isomorphic elevation of all five LD isoenzymes. Use of the last of these criteria increased the clinical sensitivity of serum LD-3 elevations in active CGL from 82% to 92%. The mean serum LD-3 absolute value and serum total LD activity usually showed statistically significant differences (P less than 0.05) among patients with active CGL, those in partial remission, and those in complete remission, but did not distinguish between subgroups of individuals with active CGL. Elevation of the serum LD-5/total LD ratio in 16 of 58 patients was due to hepatic injury or methodologic imprecision, showing analytically insignificant, borderline abnormalities in all cases of active CGL. In 10 of 62 patients in complete remission or partial remission, however, such elevation was unexplained. Our results indicate that the evaluation of serum LD-3 values in both absolute and relative terms slightly increases the clinical sensitivity of LD-3, and, therefore, suggest that LD-3 might be a useful marker for CGL.