STANDARDIZATION AND VALIDATION OF β-HYDROXYBUTYRATE QUANTIFICATION IN FELINE SERUM WITH THE BT3500 ANALYZER

Introduction: Feline diabetes mellitus is a frequent endocrinopathy. The introduction of selective sodiumglucose cotransporter type 2 (SGLT2) inhibitors has improved glycemic control but increased concern for euglycemic diabetic ketoacidosis. β-Hydroxybutyrate (β-OHB) is the predominant circulating ketone body and a sensitive indicator of ketosis. Quantitative measurement in serum provides superior accuracy compared to urine dipstick testing1-2. Objectives: This study aimed to validate the Randox enzymatic β-OHB assay for feline serum using the BT3500 chemistry analyzer, assessing precision, accuracy, linearity, detection limit, and sample stability according to ASVCP guidelines3. Methods: Surplus feline serum samples (n = 35) with varying endogenous β-OHB concentrations were pooled and analyzed. Intra- and inter-assay precision, spike-recovery accuracy, serial dilution linearity, and analytical limits (LoB, LoD, LoQ) were evaluated. Stability was assessed at 4 °C and –20 °C over time. Data were analyzed using descriptive statistics and least-squares regression. Results: Intra-assay CVs ranged from 1.7% to 14.5%, and inter-assay CVs from 3.5% to 10.6%. Recoveries were 110–122 % (mean 114 % ± 4 %). Linearity was excellent (R² > 0.998). Analytical limits were LoB = 0.044 mmol/L, LoD = 0.091 mmol/L, LoQ = 0.150 mmol/L. β-OHB remained stable for 6 days at 4 °C and at −20 °C up to 180 days, while decreases exceeding the acceptance limit were observed at 360 days. Conclusion: The Randox β-OHB assay on the BT3500 analyzer demonstrated excellent analytical performance on feline serum. The method is reliable for detecting ketosis and monitoring diabetic cats, including those under SGLT2-inhibitor therapy. References: 1Weingart C. et al. (2012). J Vet Diagn Invest 24(2): 295–300. 2Zeugswetter F. et al. (2010). J Feline Med Surg 12(4): 300–305. 3Flatland B. et al. (2010). Vet Clin Pathol 39(3): 264–277.