Comparison of procedures for the measurement of the anodal isoenzymes of lactate dehydrogenase in serum.

Lactate dehydrogenase (LD) isoenzyme-1 levels (LD1) determined after immunoprecipitation of M-subunits, LD1 activity by electrophoresis, and the activities of alpha-hydroxybutyrate dehydrogenase (HBD), urea-stable LD, and heat-stable LD, by Association of Clinical Biochemists Proposed Methods, were examined for their ability to differentiate between serum samples from patients with cardiac or liver disease. Compared with total LD, all methods gave higher serum activity in patients with cardiac disease than in those with liver disease. Differentiation between patient groups was greatest for LD1 by immunoprecipitation, followed by heat-stable LD and LD1 by electrophoresis. HBD and urea-stable LD both gave less discrimination, with negligible difference between these two procedures. LD1 activity by immunoprecipitation correlated well with LD1 activity determined by isoenzyme electrophoresis with densitometric scanning. The advantages and disadvantages of the various procedures are considered.