Prediction of future insulin‐deficiency in glutamic acid decarboxylase autoantibody enzyme‐linked immunosorbent assay‐positive patients with slowly‐progressive type 1 diabetes

Abstract

AbstractAims/IntroductionThis study aimed to identify risk factors that contribute to the progression of slowly‐progressive type 1 diabetes by evaluating the positive predictive value (PPV) of factors associated with the progression to an insulin‐dependent state.Materials and MethodsWe selected 60 slowly‐progressive type 1 diabetes patients who tested positive for glutamic acid decarboxylase autoantibodies (GADA) at diagnosis from the Japanese Type 1 Diabetes Database Study. GADA levels in these patients were concurrently measured using both radioimmunoassay (RIA) and enzyme‐linked immunosorbent assay (ELISA) techniques.ResultsCompared with the non‐progressor group (fasting C‐peptide [F‐CPR] levels maintained ≥0.6 ng/mL), the progressor group showed a younger age at diagnosis, lower body mass index (BMI), lower F‐CPR levels and a higher prevalence of insulinoma‐associated antigen‐2 autoantibodies (IA‐2A). The PPV of RIA‐GADA increased from 56.3 to 70.0% in the high titer group (≥10 U/mL), and further increased to 76.9, 84.2, 81.0 and 75.0% when combined with specific thresholds for age at diagnosis <47 years, BMI <22.6 kg/m2, F‐CPR <1.41 ng/mL and IA‐2A positivity, respectively. In contrast, the PPV of ELISA‐GADA (71.8%) remained the same at 73.1% in the high titer group (≥180 U/mL), but increased to 81.8, 82.4 and 79.0% when evaluated in conjunction with age at diagnosis, BMI and F‐CPR level, respectively.ConclusionsOur findings show that, unlike RIA‐GADA, ELISA‐GADA shows no association between GADA titers and the risk of progression to an insulin‐dependent state. The PPV improves when age at diagnosis, BMI and F‐CPR levels are considered in combination.