RESUMO
Insulin autoantibodies (IAA) of first-degree relatives of type diabetic patient and recent-onset type I diabetics were measured by radioimmunoassay. A cut-off of 60 nU/ml was established on the basis of the values of normal control individuals. The intra-assay coefficient of variation was 9.2% for a moderately positive serum (1908 ñ 176 nU/ml (mean ñ SD), N=7; range, 1708 to 2158 nU/ml). The interassay coefficient of variation was 23.8% for a negative (normal control) serum (28.1 ñ 6.7 nU/ml, N=6; range, 22 to 39 nU/ml) and 14.5% in a highly positive serum (6185 ñ 899 nU/ml, N=7; range, 5053 to 7009 nU/ml). Insulin autoantibody levels (mean ñ SEM) were 19.3 ñ 2.8 nU/ml (range, =-19 to 40 nU/ml) in 25 controls, 24.8 ñ 3.4 nU/ml (range, -17 to 59 nU/ml) in 41 type II diabetic patients, 18.5 ñ 2.4 nU/ml (range, -58 to 268 nU/ml) in 171 first-degree relatives of type I diabetic patients and 208.9 ñ 87.0 nU/ml (range, 10 to 1101 nU/ml) in 16 recent-onset type I diabetic patients. IAA levels were significantly higher in the last group compared with the other groups (P<0.01). None of the controls or type II diabetics exceeded the upper limit of normalyity. In contrast, 9 of 171 (5.3%) first-degree relatives and 9 of 16 (56.0%) recent-onset type I diabetic patients had IAA levels above the 60 nU/ml cut-off point. These data indicate that this method is effective for the detection of individuals who are at high risk to develop type I diabetes