Comparison of anti-human insulin antibodies detection by commercial enzyme-linked immunosorbent assay kit, displacement enzyme-linked immunosorbent assay and radioimmunoassay, in Thai diabetic patients.

Antibodies specific to human insulin, in sera of Thai diabetic patients and normal healthy individuals, were detected by a commercial enzyme-linked immunosorbent assay (ELISA) kit, displacement ELISA and radioimmunoassay (RIA). Among 36 insulin-treated patients, the antibodies were detected in 22, 23 and 20 individuals, by RIA, commercial ELISA kit and displacement ELISA, respectively. Among those who had never previously received insulin therapy, RIA showed positive results in 5/11 patients with insulin-dependent diabetes mellitus (IDDM) and 1/2 patients with fibrocalculous pancreatic diabetes (FCPD); but were negative in all 26 patients with non-insulin-dependent diabetes mellitus (NIDDM) and 30 normal healthy individuals. The commercial ELISA kit could detect such insulin autoantibodies (IAA) in 4/11 IDDM, 3/26 NIDDM, 2/2 FCPD patients and 4/30 normal controls; while the displacement ELISA showed positive IAA detection in 5/11 IDDM, 2/26 NIDDM, 2/2 FCPD and 2/30 normal controls. By using RIA as the 'gold standard', the commercial ELISA kit had 92.86% sensitivity, 87.01% specificity, 88.57% accuracy, 72.22% positive predictive value and 97.10% negative predictive value; while these indices for the displacement ELISA were 85.71%, 90.01%, 89.52%, 77.42% and 94.59%, respectively.