Validation and comparison of two methods of measuring lactate in equine plasma.
CONCLUSIONS



BACKGROUND
Some methods of lactate (LA) measurement have not been validated appropriately for use in horses.


OBJECTIVE
To validate 2 LA analysers (YSI 2300 Stat Plus and TDx Lactic Acid Assay) for use with equine plasma and to compare plasma [LA] determined by the 2 methods.


METHODS
Both instruments were evaluated for linearity, parallelism, recovery and precision using serial dilutions of standard LA solutions and equine plasma and then comparing results with linear regression or paired t tests. Plasma [LA] results were compared in 275 blood samples collected from horses exercising at various intensities using Bland-Altman analysis. Level of significance was P < 0.05.


RESULTS
YSI exhibited good linearity for both LA standards and equine plasma (P < 0.05) at 0-30 mmol/l. TDx had good linearity at 0-12 mmol/l (P < 0.05); with LA standard solutions >12 mmol/l and with equine plasma, linearity was decreased. YSI exhibited good parallelism between LA standards and equine plasma LA measurements throughout the 0-30 mmol/l range (P > 0.05). Parallelism was poor with TDx (P < 0.05). Mean ± s.d. % recovery was 101.7 ± 3.4% for YSI (acceptable) and 110.6 ± 8.4% for TDx (unacceptable). Within-run and mean between-run coefficients of variation (CV) for plasma samples tested from 3.3-29.5 mmol/l were 0.4-3.0% for YSI. CVs for samples tested from 2.8-8.0 mmol/l were 17.4-24.1% for TDx. In 275 plasma samples, [LA] ranged from 0.1-42.7 mmol/l and 0.3-50.6 mmol/l for the YSI and TDx methods, respectively. The difference in plasma [LA] determined by the 2 methods was -1.0 ± 3.2 mmol/l, documenting that the TDx overestimated the YSI results by a mean value of 1 mmol/l.


CONCLUSIONS
It was concluded that the YSI method was a reliable method for measuring equine plasma [LA] from 0-30 mmol/l. The TDx method was found not to be suitable for use with equine plasma due to greater variability in measurements (high CV).
Department of Medicine, Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. navichaya@kku.ac.th
P
P
Butudom
J H
JH
Foreman
K H
KH
Kline
E L
EL
Whittem
D000818:Animals; D001774:Blood Chemical Analysis / Q000295:instrumentation / Q000662:veterinary*; D006736:Horses / Q000097:blood*; D019344:Lactic Acid / Q000097:blood*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D019344:Lactic Acid