Biological variation of lactate and pyruvate in blood.

Measurement of lactate and pyruvate in whole blood is valuable in critical-care medicine and exercise physiology. However, information on the biological variability of lactate and pyruvate is lacking, a fact that may seem surprising when one considers the many reports on lactate and pyruvate as indicators of the state of tissue oxidation. To investigate the analytical and biological variation of these analytes, we took five blood specimens from each of eight apparently healthy laboratory workers (three men and five women, ages 25 to 47 years) once a day for 5 consecutive days. Preanalytical sources of variance were minimized. Protein-free specimens (trichloroacetic acid was used as protein precipitant) were stored at -20 #{176}C until asialyzed. When all the specimens were available, they were thawed, mixed, and centrifuged for analysis in a single run in duplicate, in random order. Lactate and pyruvate were measured enzymatically as previously described (1, 2). Biological within-subject variance was estimated from the total within-subject variance minus withinrun analytical variance. The latter was estimated from replicate analyses of specimens from the subjects themselves. Biological between-subject variance was estimated from the total variance of the set of duplicate data from the assay performed on each subject minus analytical and within-subject components (3). All the components of variation were then transformed to the relevant coefficients of variation by using the overall mean. The means and components of variation [analytical variation (CVA), intraindividual variation (CV1), and interindividual biological variation (CV&] were as follows: