ASSESSMENT OF THE LACTATE BIOSENSOR METHODOLOGY

The rapid determination of lactate level is useful for clinical emerge ncies, as in the case of shock conditions or during surgical operation s, as well as in numerous cases of respiratory failure, in cardiac or paediatric pathology and during exercise tests. Moreover, it is of pro gnostic significance in critically ill patients, Photometric methods a re slow and, even when performed in good conditions, will give results only 30 min after blood collection, during which time the clinical co ndition 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 mu L of biological fluid. In order to test th e validity of this method, we performed comparisons between the Sigma classical enzymatic reference method and two commercially available bi osensors: the Ciba-Corning biosensor 865 and the Yellow Springs lactat e biosensor. Lactate measurements were performed in heparinized arteri al blood samples without antiglycolitic agent (n=71). In order to cove r a wide range of lactate levels, samples came from patients admitted to the intensive care unit for severe conditions and patients addresse d 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 potent ially influence lactate measurement were also investigated: haematocri t and total protein levels. The data showed that measurements performe d on plasma are satisfactory for both biosensors. For whole blood, the Ciba-Corning device gives accurate results but the Yellow Springs app aratus seriously underestimates lactate levels. This underestimation i s strongly influenced by the haematocrit level, so that a correction f actor can be calculated (based on the haemoglobin level), which allows accurate ''corrected'' results to be obtained for whole blood with th e Yellow Springs analyser.