An automated colorimetric (tetrazolium salt) assay for serum lactate dehydrogenase.

The adaptation of a tetrazolium salt assay for serum lactate dehydrogenase to full automation is described. The tetrazolium salt, INT, (2-p-iodophenyl-3-p-nitrophenyl5-phenyl tetrazolium chloride) serves as the chromogenic indicator of the enzyme activity. Phenazine methosulfate serves as an intermediate electron carrier. Estimation requires only 5 mm. of incubation, and assays may be run at the rate of 60/hr. Comparison against the manual version of the assay with respect to normal and abnormal serum activity levels is excellent.