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Clinica chimica acta; international journal of clinical chemistry

Development of an enzymatic assay to measure lactate in perchloric acid-precipitated whole blood.


PMID 25727513

Abstract

The lactate to pyruvate (L:P) ratio is used to identify the cause of a lactic acidosis. Because tests for whole blood lactate and pyruvate require different sample types, the accuracy of the L:P ratio may be compromised by preanalytical errors. The measurement of lactate in the sample required for pyruvate is desirable. Whole blood was added to 8% perchloric acid to obtain a protein-free supernatant. Lactate was measured by its oxidation to pyruvate and hydrogen peroxide by lactate oxidase. Assay accuracy, imprecision, analytical sensitivity, linearity, analyte stability, and a reference interval were determined. Deming regression of lactate results from paired plasma and supernatant produced a slope of 0.95 and y-intercept of -0.37 mmol/l (R(2)=0.95). Recovery of lactate added to supernatant ranged from 103.4 to 112.7%. Within-laboratory CVs were 6.1% and 1.1% at 1.58 and 10.89 mmol/l, respectively and between-day CVs were 2.3% and 0.9%, respectively. The limit-of-detection was 0.18 mmol/l and the assay was linear to 13.15 mmol/l. Lactate in the supernatant was stable for a minimum of 8h, 21 days, or 6 months at room temperature, 4-8°C, and -20°C, respectively. The lactate reference interval was 0.31-2.00 mmol/l from 116 healthy adults. Lactate can be quantified in the same protein-free supernatant used for the measurement of pyruvate allowing the calculation of the L:P ratio from a single specimen.