Lactate determination in exercise testing using an electrochemical analyser: with or without blood lysis?

The practical use of lactate electrochemical analysers in exercise testing has not been adequately examined. Initial studies have reported differences in lactate concentration between that measured spectrophotometrically and that measured electrochemically. The study described here was undertaken to compare, using the statistical technique of Bland and Altman (1986), two w idely available methods of measuring lactate using lysed and non-lysed bloo d samples and the lactate thresholds derived from the measured lactate valu es using a log-log transform technique, Thirteen normal, healthy young adul ts (11 male) undertook progressive exercise tests to exhaustion. Arterialis ed venous blood samples were taken each minute and the lactate concentratio n therein was measured both spectrophotometrically and electrochemically an d either with or without lysis of the blood samples. The lactate concentrat ions measured in lysed blood using both methods (182 pairs) were in close a greement. The electrochemical values obtained using non-lysed blood were sy stematically lower than spectrophotometric values (206 pairs), the differen ce becoming progressively greater at higher lactate concentrations. Results for the lactate threshold comparisons are given as mean difference (limits of agreement with 95% probability). Lactate thresholds (12 pairs) derived from lysed blood lactate concentrations measured spectrophotometrically and electrochemically were not significantly different -30 (240) mi O-2 . min( -1). Lactate thresholds (11 pairs) derived from lysed spectrophotometric an d non-lysed electrochemical measurements were also not significantly differ ent + 20 (250) ml O2 . min(-1). Thus, despite the difference in the measure d lactate concentrations, the derived lactate thresholds are in agreement a nd, therefore, electrochemical analysers can be used for lactate threshold determination using the log-log transform technique without sample lysis.