Research Associate Tufts Cummings School of Veterinary Medicine North Grafton, Massachusetts, United States
Abstract:
Background: Low-dose (LD) and high-dose (HD) oral sugar tests have been compared in ponies, but further investigation is required in horses.
Hypothesis: That the HD-oral sugar test (OST) would induce significantly higher blood glucose (BG) and insulin concentrations than the LD-OST.
Animals: Twenty-four adult horses (median age 16 years) of unknown insulin status.
Methods: Horses were administered a LD-OST and a HD-OST (0.15 and 0.45 mL Karo syrup per kg body weight, respectively) 7 days apart. Test order was randomly assigned. Blood was collected at T0, T60, and T90 minutes, with BG measured using a handheld glucometer and insulin measured using radioimmunoassay at a commercial veterinary laboratory. Results were compared using Wilcoxon matched-pairs signed-rank testing and bias between methods was assessed using Bland-Altman plots.
Results: Median BG and insulin at T0 were not significantly different between methods (P > 0.05). Median BG and insulin were significantly higher for the HD-OST than the LD-OST at both T60 (P < 0.02) and T90 (P < 0.01). Mean bias for HD-OST glucose concentrations was 6.8% at T60 and 10.5% at T90, compared to the LD-OST. Mean bias for HD-OST insulin concentrations was 35.4% at T60 and 44.1% at T90 compared to the LD-OST. Using established cutoffs, ID was diagnosed in 1 horse using the LD-OST and 2 horses using the HD-OST.
Conclusion: HD-OST yielded significantly higher BG and insulin concentrations at both T60 and T90 than LD-OST. Test performance should now be investigated in horses with results that fall closer to cutoff values.
