Influence of glycosylated hemoglobin on sight-threatening diabetic retinopathy: a population-based study.

Aim: To evaluate the role of glycosylated hemoglobin (HbA1c) on the occurrence of sight-threatening diabetic retinopathy (STDR) in urban Chennai, Tamil Nadu, India.

Methods: A total of 5999 individuals were enumerated from the Chennai metropolis. Of these, 1414 subjects with diabetes were included for data analysis in the study. STDR or non-STDR groups were classified based on the fundus photographs. HbA1c was measured (Bio-Rad DiaSTAT™ HbA1c Reagent Kit) by the liquid chromatography technique.

Results: A statistically significant difference (p < 0.05) was noted in the duration of diabetes, gender, body mass index, HbA1c, micro- and macro-albuminuria between both non-STDR and STDR groups as compared to the no-diabetic retinopathy (DR) group. On multivariate analysis, HbA1c (non-STDR: odd's ratio OR = 1.23; 95% confidence interval CI = 1.15-1.32; p < 0.0001; STDR: OR = 1.31 95% CI = 1.14-1.52; p < 0.0001) was found to be significantly associated with non-STDR and STDR when compared with the no-DR group. The Receiver Operating Characteristic analysis showed that the cut-off value of 8.0 had 75.6% sensitivity and 58.2% specificity with 64.9% maximum area under the curve.

Conclusion: HbA1c value >8.0% was significantly related with STDR. In a screening programme, the cut-off value of HbA1c >8.0% provided a maximum yield of STDR.