Predictive value of age-related acute insulin response to glucose in subjects at risk for type 1 diabetes: results of a 6-year follow-up study from west-France.

The acute insulin response to i.v. glucose (AIRG) was evaluated in 344 first-degree relatives of patients with Type 1 diabetes. In 318 relatives aged 3 to 48 years without islet cell antibody and insulin autoantibody, correlations (p < 0.0006) were found between age and fasting insulinaemia, fasting glycaemia, or AIRG, with a peak during puberty. Assuming that these relatives without islet cells and insulin auto-antibodies have a low risk of developing Type 1 diabetes, we provided a "standard age-related chart" for AIRG with a "low" AIRG defined as a value below the 1st percentile for each pubertal stage. Using these cut-off points, predictive characteristics of a low AIRG for progression towards diabetes within 6 years were analysed. Four relatives developed diabetes and one displayed impaired oral glucose tolerance. Four out of these 5 subjects had islet cell and insulin auto-antibodies, but the other one was negative for these markers. Three of these 5 subjects had low AIRG at entry (30, 24 and 1 months before diabetes, respectively). The two others displayed a steady progressive decline (p < 0.02) of age-related during the follow-up before impaired oral glucose tolerance and diabetes appeared (rate of decline: 15 microU/ml/year). Thus, independently of the presence of islet cell antibodies, the predictive value of a low age-related AIRG during the follow-up is greater than the single low AIRG at entry.(ABSTRACT TRUNCATED AT 250 WORDS)