The use of NADH as a standard in a modified PMS-INT colorimetric assay of lactate dehydrogenase

A new and more reliable way of quantitating lactate dehydrogenase activity, using NADH as a standard in a colorimetric assay, is proposed. Adopting the scheme, we obtained a CV of 2.6% and precision (95% limits) of +/-5.4% for enzyme activities ranging from 110 to 600 U/l. Comparative study against the modified kinetic method of Amador et al. showed excellent correlation, r = 0.99, p less than 0.001. A normal range of 75 to 203 U/l was determined for the proposed scheme.