Optimisation of the frequently sampled intravenous glucose tolerance test to reduce urinary glucose spilling in horses.
Authors: Tóth F, Frank N, Elliott S B, Perdue K, Geor R J, Boston R C
Journal: Equine veterinary journal
Summary
# Editorial Summary The frequently sampled intravenous glucose tolerance test (FSIGTT) has become the gold standard for assessing insulin sensitivity and glucose handling in horses, yet the standard protocol causes significant urinary glucose spillage that may confound interpretation of results. Tóth and colleagues investigated whether adjusting dextrose and insulin dosages could minimise this problem in six mares, testing six different dextrose doses (ranging from 75–600 mg/kg bodyweight) and six insulin doses, whilst measuring both glucose and insulin dynamics using minimal model analysis and quantifying urinary glucose loss across protocols. The established FSIGTT protocol using 300 mg/kg dextrose produced substantial glucose spillage; however, reducing the dextrose dose to 100 mg/kg markedly decreased urinary losses without compromising the mathematical modelling of insulin sensitivity or glucose effectiveness. The researchers therefore recommend adopting a revised protocol using 100 mg/kg dextrose followed by 20 IU/kg insulin administered 20 minutes later, which maintains diagnostic validity whilst eliminating a significant source of measurement error. For practitioners involved in metabolic assessment of horses—particularly those screening for insulin dysregulation or equine metabolic syndrome—this optimised protocol offers greater reliability and confidence in the interpretation of insulin sensitivity values when evaluating clinical cases or research populations.
Read the full abstract on PubMed
Practical Takeaways
- •If your practice uses FSIGTT testing for metabolic evaluation, the lower dextrose dose (100 mg/kg bwt) provides more reliable results with reduced urinary glucose loss that can confound interpretation
- •The new optimized protocol is more practical for clinical use as it reduces complications from excessive glucose spillage while giving the same diagnostic information
- •UGS is a real phenomenon in standard FSIGTT that can affect results—ensure your laboratory or diagnostic facility uses the optimized protocol for accurate glucose and insulin dynamics assessment
Key Findings
- •Urinary glucose spilling occurs during all FSIGTT procedures in horses, highest with the established protocol using 300 mg/kg bwt dextrose
- •Dextrose dosage of 300 mg/kg bwt in the established FSIGTT is excessive, with AUCg plateau achieved at ≥200 mg/kg bwt
- •Reducing dextrose dosage to 100 mg/kg bwt minimizes urinary glucose spilling while maintaining adequate data for minimal model analysis
- •New optimized FSIGTT protocol (100 mg/kg bwt dextrose + 20 mU/kg bwt insulin at 20 min) reduces UGS compared to established protocol without affecting minimal model results