Examination of four different instruments for measuring blood lactate concentration.

Information on the performance of different instruments used to measure blood lactate concentration is incomplete. We therefore examined instruments from Yellow Springs Instruments (YSI 23L and YSI 1500) and three cheaper and simpler instruments: Dr. Lange's LP8+, Lactate Pro from Arkray in the KDK corporation and Accusport from Boehringer Mannheim. First, a number of blood samples were analysed by standard enzymatic photofluorometry (our reference method) and, in addition, by one or more of the instruments mentioned above. Second, measurements using two or more identical instruments were compared. Third, since Lactate Pro and Accusport are small (approximately 100 g, pocket-size), battery-driven, instruments that could be used for outdoor testing, the performance of these instruments was examined at simulated altitudes (O2 pressure of <10 kPa) and at temperatures below -20 degrees C, while screening the instruments as much as possible from the cold. Most of the different instruments showed systematically too high or too low values (10-25% deviation). The observed differences between instruments may affect the "blood lactate threshold" by 2-5%. We found different readings between "equal" YSI 1500 instruments, while we could see no difference when comparing the other instruments of the same type. Lactate Pro gave reliable results at both -21+/-1 degrees C and at simulated altitude. Accusport gave reliable results in the cold, but 1.85+/-0.08 mmol L(-1) (mean+/-SD) too high readings at the simulated altitude. Of the three simpler instruments examined, the Lactate Pro was at least as good as the YSI instruments and superior to the other two.