Objective—To determine reference values and test
variability for glucose tolerance tests (GTT), insulin tolerance
tests (ITT), and insulin sensitivity tests (IST) in
Animals—32 clinically normal cats.
Procedure—GTT, ITT, and IST were performed on
consecutive days. Tolerance intervals (ie, reference
values) were calculated as means ± 2.397 SD for plasma
glucose and insulin concentrations, half-life of glucose
(T1/2glucose), rate constants for glucose disappearance
(Kglucose and Kitt), and insulin sensitivity
index (SI). Tests were repeated after 6 weeks in 8 cats
to determine test variability.
Results—Reference values for T1/2glucose, Kglucose, and
fasting plasma glucose and insulin concentrations
during GTT were 45 to 74 minutes, 0.93 to 1.54
%/min, 37 to 104 mg/dl, and 2.8 to 20.6 µU/ml,
respectively. Mean values did not differ between the
2 tests. Coefficients of variation for T1/2glucose, Kglucose,
and fasting plasma glucose and insulin concentrations
were 20, 20, 11, and 23%, respectively. Reference
values for Kitt were 1.14 to 7.3%/min, and for SI were
0.57 to 10.99 × 10-4 min/µU/ml. Mean values did not
differ between the 2 tests performed 6 weeks apart.
Coefficients of variation for Kitt and SI were 60 and
Conclusion and Clinical Relevance—GTT, ITT, and
IST can be performed in cats, using standard protocols.
Knowledge of reference values and test variability
will enable researchers to better interpret test
results for assessment of glucose tolerance, pancreatic
β-cell function, and insulin sensitivity in cats. (Am
J Vet Res 2001;62:630–636)