Peer Review #2 of "Validation of a handheld β-hydroxybutyrate acid meter to identify hyperketonaemia in ewes (v0.2)"

Abstract

Background. The end of pregnancy is the period with the highest risk of occurrences of ketosis and pregnancy toxaemia due to fat mobilization and increasing non-esterified fatty acids in the liver which are converted in ketone bodies, mainly β-hydroxybutyrate acid (BHB). This ketone body may also become elevated in the bloodstream. The present study validates the use of a handheld meter for determining the blood concentration of BHB and ascertaining the predictive value and accuracy of BHB measurements in diagnosing hyperketonaemia in ewes. Methods. Nineteen, non-pregnant, crossbred ewes were subjected to two hours of intravenous infusion of a saturated BHB solution. Over six hours of evaluation, 247 blood samples were obtained in 13 sampling moments. The BHB concentration was measured by an enzymatic colorimetric method in an automated biochemical analyser (gold-standard) and by a handheld meter using an electrochemical enzyme technique. Results. There was a high correlation between both methods (r = 0.98; P < 0.001). Considering the blood BHB concentrations range 0.8-1.6 mmol/L for moderate ketosis the handheld meter presented sensitivity and specificity of 0.98 and 0.81, respectively. For severe ketosis (BHB ≥ 1.6 mmol/L) sensitivity and specificity were 0.99 and 0.75, respectively. Thus, the handheld device can be useful for diagnoses of cases of mild or severe pregnancy toxaemia at field conditions.