[Evaluation of lactate measurement in blood and plasma with biosensor technology: a comparison of methods]

The introduction of biosensor technology for near bedside measurement of plasma lactate concentrations has been a promising step for critical care profiling. However, methodological drawbacks and relevant inaccuracy have been reported. With the advent of a new biosensor (Chiron Diagnostics) and a revised NOVA Biomedical device, accuracy was expected to be improved. The goal of the present investigation was to evaluate the accuracy of both methods.

Two devices (System 860, Chiron Diagnostics; StatProfile 9, NOVA Biomedical) were simultaneously analysed using 9 biosensors in both fresh frozen plasma and citrated whole blood. The results were compared with an established photometric method (Lactat PAP, Analyticon). Measurements were performed as duplicates (n = 1120) before and after the addition of 1 molar sodium lactate solution (2-24 mmol/L). For the estimation of between-day precision commercially available aqueous and serum-based quality controls were analysed daily over a period of 60 days.

Reproducibility in blood was 2.6 +/- 2.8% (Chiron), 4.1 +/- 4.0% (NOVA) and 1.5 +/- 2.1% (Analyticon), in plasma respectively 2.1 +/- 2.4%, 2.1 +/- 2.9% and 1.0 +/- 1.1%. Mean inaccuracy in plasma presented to be -0.2 +/- 16.4% (plasma) and +7.2 +/- 13.1% (blood) for Chiron, +9.4 +/- 18.4% and +18.7 +/- 16.7% for NOVA, and -37.8 +/- 18.2% and -27.5 +/- 17.6% for Analyticon. Calculated between-day-precision (variation coefficients mean values) was 11.5 +/- 4.9% (Chiron) and 14.0 +/- 5.9% (NOVA).

Although accuracy of lactate concentrations obtained with biosensor technology has improved (mean 0-18%), the variability of the results still poses a problem (mean 13-18%). Therefore, from the methodological point of view, interpretation of a single lactate value requires caution when applying to the critically ill, particularly with view to threshold values, and should be considered vis-à-vis other options.