Evaluation of a biosensor for the measurement of lactate in whole blood.

OBJECTIVES: Evaluation of the analytical performance of a biosensor for the measurement of lactate in whole blood samples and comparison of the results of patients samples with a routinely used spectrophotometric enzymatic method. DESIGN AND METHODS: Heparinized whole blood samples of patients and aqueous control samples were used to determine precision and carry-over. For comparison of the lactate biosensor and the enzymatic method human blood samples were split and measured. RESULTS: Satisfactory within-run (n = 7) and day-to-day (n = 15) precision was found, while carry-over was minimal (<0.2%). A statistically significant relation between the lactate levels in whole blood samples (n = 31) and the corresponding plasma samples was found: y = 0.98x - 0.05 and r = 1.00. No correlation was found between the hematocrit (range 0.23-0.51) and the difference in lactate concentration between plasma and whole blood. When comparing patient results (n = 722) obtained with the spectrophotometric method and the biosensor method, the biosensor measured 13% higher lactate levels. A correction on the basis of the hematocrit minimized this difference. CONCLUSION: The combination of analytical performance, easy handling, rapid analysis, and measurement in whole blood makes the biosensor suitable for lactate STAT-analyses. Care must be given to the interpretation of the results as well as to the preanalytical aspects.

Rapid and reliable measurement of highly elevated blood ammonia concentrations in children.

Newborns and children may suffer from extremely high ammonia levels in their blood. We evaluated a fast, reliable micromethod, based on the Blood Ammonia Checker II (BAC II) in combination with the dilution with fresh whole blood. Comparison of the proposed method with an enzymatic method revealed a statistically significant correlation. We conclude that the dilution of patient's blood with fresh whole blood extends the measuring range of ammonia on the BAC II analyzer from 286 mumol/l to about 700 mumol/l.