Technical note: Comparison of 4 electronic handheld meters for diagnosing hyperketonemia in dairy cows

The objective of this study was to evaluate 4 handheld ketone meters for use in on-farm β-hydroxybutyrate (BHB) monitoring of hyperketonemia in transition dairy cows. Blood samples taken from 250 Holstein cows between 262 d pregnant and 15 d in milk were evaluated on 4 different handheld ketone meters: Precision Xtra (Abbott Laboratories, Abbott Park, IL), TaiDoc (Pharmadoc, Lüdersdorf, Germany), Nova Max (Nova Biomedical, Billerica, MA), and Nova Vet (Nova Biomedical). Samples were screened using the Precision Xtra and tested on the remaining 3 m if the sample BHB concentration fell into predetermined ranges. A total of 89 samples were used for analysis. Performance of each meter was compared with the average of 2 plasma BHB concentrations both determined by a gold standard spectrophotometric Randox assay performed at 2 independent laboratories. Agreement between the 2 laboratories was very strong (Pearson correlation = 0.998). All meters had Pearson correlation coefficients greater than 0.95. The Precision Xtra and TaiDoc meters were 100.0% sensitive and 73.5% specific at a BHB concentration cut point of 1.2 mmol/L. The Nova Vet and Nova Max meters had sensitivities of 94.9 and 74.4% and specificities of 91.8 and 100.0%, respectively, at the same cut point. Agreement between the gold standard and the handheld meter was the best for the Nova Vet meter when evaluated using a Bland Altman graph with a mean BHB difference of 0.08 mmol/L. Trends in bias were noted with the Precision Xtra and Nova Max meters resulting in increasing average discrepancy between the gold standard and the meter for both at higher plasma BHB concentrations and mean BHB differences of −0.34 and 0.26 mmol/L, respectively. The coefficient of variation was <10% for the Precision Xtra, TaiDoc, and Nova Vet meters, and <15% for the Nova Max meter. We conclude that the TaiDoc and Nova Vet meters, similar to the already validated Precision Xtra meter, are acceptable for use in on-farm testing for monitoring and treatment of hyperketonemia.