Colorimetric measurement of D(-)lactate in plasma.

We describe a method for the direct assay of D(-)lactate in plasma using D(-)lactate dehydrogenase and a color reagent to produce a formazan color measured at 510 nm. This method agrees well with a modified lactate UV end-point method r = 0.998 and the regression equation y = 0.974x + 0.13. The precision for low and high concentrations of D(-)lactate is 4.8% and 3.6% within-batch and 8.9% and 1.7% between-batch. Recoveries average 105% and 98% for D(-)lactate at concentrations of 1 and 5 mmol/L, respectively. The proposed method is inexpensive and suitable for routine and emergency use, and shares reagents used for the assay of L(+)lactate and 3-hydroxybutyrate.