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

The researchers compared two methods of measuring lactate levels in horse plasma and concluded that the YSI method is more reliable while the TDx method showed greater variability and was less suited for this use.

Methods used in the study

• The scientists aimed to validate two lactate analysers (YSI 2300 Stat Plus and TDx Lactic Acid Assay) to assess their suitability for use with equine plasma.
• The measuring instruments were tested for linearity, parallelism, recovery and precision. These evaluations were performed by carrying out serial dilutions of standard lactate solutions and equine plasma and then analyzing the results with linear regression or paired t test methods.
• A set of 275 blood samples were assessed, collected from horses exercising at different intensity levels. The results were compared using a statistical method known as Bland-Altman analysis.

Results of the study

• The YSI analyzer displayed good linearity for measurement of both lactate standards and equine plasma up to levels of 30 mmol/l, suggesting it is highly accurate. In contrast, while the TDx analyzer also showed good linearity up to 12 mmol/l, it demonstrated decreased accuracy for higher concentrations.
• In terms of parallelism (a method used to ascertain whether the relationship between two different measurements remains constant over a range of different concentrations), the YSI analyzer again performed well compared to the TDx which performed poorly.
• Recovery rates were also compared, and here too, the YSI tool had better performance (101.7 ± 3.4%) than the TDx system (110.6 ± 8.4%). This shows that the YSI recovery rate is within acceptable ranges while TDx’s rate is not.
• The two methods also differ significantly in their within-run and between-run coefficients of variation (CV), which measure method reliability. The YSI system displayed far less variation compared to the TDx
• In a comparison of 275 plasma samples, it was found that the TDx system overestimated lactate readings by a mean value of 1 mmol/l compared to the YSI, adding further to evidence of its inferior performance.

Conclusion

• Based on the extensive testing carried out, the researchers concluded that the YSI method was a reliable and well-performing method for measuring lactate in horse plasma in the range of 0-30 mmol/l.
• The TDx method demonstrated higher variability and generally poorer performance, making it less suitable for use with equine plasma.