Assessment of the lactate biosensor methodology.

The rapid determination of lactate level is useful for clinical emergencies, as in the case of shock conditions or during surgical operations, as well as in numerous cases of respiratory failure, in cardiac or paediatric pathology and during exercise tests. Moreover, it is of prognostic significance in critically ill patients. Photometric methods are slow and, even when performed in good conditions, will give results only 30 min after blood collection, during which time the clinical condition of the patient may change. In this study, we have assessed the lactate biosensor, a method that yields lactate measurements in less than 1 min with only 100 microL of biological fluid. In order to test the validity of this method, we performed comparisons between the Sigma classical enzymatic reference method and two commercially available biosensors: the Ciba-Corning biosensor 865 and the Yellow Springs lactate biosensor. Lactate measurements were performed in heparinized arterial blood samples without antiglycolitic agent (n=71). In order to cover a wide range of lactate levels, samples came from patients admitted to the intensive care unit for severe conditions and patients addressed for bicycle exercise testing. Each whole blood sample was processed in duplicate by both biosensors. For plasma measurement, subsamples of whole blood were centrifuged and the resulting plasma were processed by the biosensors and the Sigma method. Two parameters that can potentially influence lactate measurement were also investigated: haematocrit and total protein levels. The data showed that measurements performed on plasma are satisfactory for both biosensors. For whole blood, the Ciba-Corning device gives accurate results but the Yellow Springs apparatus seriously underestimates lactate levels. This underestimation is strongly influenced by the haematocrit level, so that a correction factor can be calculated (based on the haemoglobin level), which allows accurate "corrected" results to be obtained for whole blood with the Yellow Springs analyser.