Predictive value of HbA1c for incident diabetes among subjects with impaired glucose tolerance--analysis of the Indian Diabetes Prevention Programmes

Abstract

Aims: The objectives of the study were to assess the predictive value of baseline HbA(1c) for incident diabetes among the participants with impaired glucose tolerance in the Indian Diabetes Prevention Programmes 1 and 2.

Methods: Data at baseline and at 3-year follow-up were analysed in combined cohorts of the Indian Diabetes Prevention Programmes 1 and 2. Within the 3 years, 324 of the 845 participants developed diabetes (World Health Organization criteria). The predictive value of baseline HbA(1c) for incident diabetes was determined by logistic regression analysis.

Results: Baseline HbA(1c) values had heterogenous distribution. The distribution was similar in isolated impaired glucose tolerance or in impaired glucose tolerance in combination with impaired fasting glucose. A progressive increase in diabetes occurred with increasing HbA(1c). HbA(1c) showed the strongest association with incident diabetes in the multiple logistic regression analysis (odds ratio 3.548, P < 0.0001). The cut-off HbA(1c) of 43 mmol/mol (6.05%) had 67% sensitivity and 60% specificity to predict future diabetes. The diagnostic sensitivity of HbA(1c) of ≥ 48 mmol/mol (≥ 6.5%) was only 51%, with a specificity of 87%, when compared with the oral glucose tolerance glucose values.

Conclusions: Baseline HbA(1c) was highly predictive of future diabetes in Asian Indian subjects with impaired glucose tolerance and nearly 60% of the incidence occurred with values ≥ 42 mmol/mol (≥ 6.0). Diagnostic sensitivity of HbA(1c) ≥ 48 mmol/mol (≥ 6.5%) for new diabetes was only 51% using the oral glucose tolerance test as the standard for comparison.