Aims/hypothesis The aims of this study were to assess the clinical significance of introducing HbA1c into a risk score for diabetes and to develop a scoring system to predict the 5 year incidence of diabetes in Japanese individuals. Methods The study included 7,654 non-diabetic individuals aged 40-75 years. Incident diabetes was defined as fasting plasma glucose (FPG) ≤7.0 mmol/l, HbA1c ≤6.5% (48 mmol/mol) or self-reported clinician-diagnosed diabetes. We constructed a risk score using non-laboratory assessments (NLA) and evaluated improvements in risk prediction by adding elevated FPG, elevated HbA1c or both to NLA. Results The discriminative ability of the NLA score (age, sex, family history of diabetes, current smoking and BMI) was 0.708. The difference in discrimination between the NLA + FPG and NLA + HbA1c scores was non-significant (0.836 vs 0.837
p=0.898). A risk score including family history of diabetes, smoking, obesity and both FPG and HbA1c had the highest discrimination (0.887, 95% CI 0.871, 0.903). At an optimal cut-off point, sensitivity and specificity were high at 83.7% and 79.0%, respectively. After initial screening using NLA scores, subsequent information on either FPG or HbA1c resulted in a net reclassification improvement of 42.7% or 52.3%, respectively (p&lt
0.0001). When both were available, net reclassification improvement and integrated discrimination improvement were further improved at 56.7% (95% CI 47.3%, 66.1%) and 10.9% (9.7%, 12.1%), respectively. Conclusions/interpretation Information on HbA1c or FPG levels after initial screening by NLA can precisely refine diabetes risk reclassification. © Springer-Verlag 2012.