Research Communications of the 27(th) ECVIM-CA Congress: Intercontinental, Saint Julian's, Malta, 14th to 16th September 2017

Serial blood samples of diabetic cats were prospectively recruited from first opinion UK veterinary practices within 180 days of initiating insulin treatment. Serum IGF-1 and basal serum endogenous insulin were evaluated using a validated and commercially offered RIA and ELISA, respectively; the latter in untreated diabetic cats only. Mann Whitney test was used to compare groups and Spearman rank correlation coefficient to assess correlation between endogenous insulin and IGF-1; P < 0.05 was considered significant. Serial blood samples of 219 cats were recruited (two samples: 103 cats; three: 55; four: 44; ≥ five: 17). Sixty-two (28.3 %) cats had at least one IGF-1 measurement >1000 ng/mL (median 1576 ng/mL, range 1001->2000); a median of 0.6 units/kg/injection insulin (range 0-2.4) was administered. Of the cats with IGF-1 >1000 ng/mL, 20 (9.1 %) initially showed IGF-1 <1000 ng/mL; therefore, the attending clinician could have discarded the possibility of HS in these patients. Median subsequent IGF-1 increase was 594 ng/mL (range 71-1495), having initially received a median of 73 days of insulin treatment (range 25-154). Basal endogenous insulin in untreated diabetic cats with IGF-1 <1000 ng/mL (n = 106; median 29.0 ng/L, range 9.2-791) was significantly lower than in those with IGF-1 >1000 ng/mL (n = 15; median 64.2 ng/L, range 9.2-490; P = 0.024). A moderate positive correlation (r s = 0.42, P < 0.0001) was detected between endogenous insulin and IGF-1 in untreated cats. In this study, approximately 1 in 10 newly diagnosed diabetic cats with an IGF-1 suggestive of underlying HS, based on the currently advocated cut-off, will initially show a negative value using this cut-off. Lower endogenous insulin, which moderately correlates with IGF-1, and/or suboptimal current cut-off value advice, could be contributing factors.