A combination of HbA1c, fasting glucose and BMI is effective in screening for individuals at risk of future type 2 diabetes: OGTT is not needed.

OBJECTIVE: To identify a screening model that predicts high risk of future type 2 diabetes and is useful in clinical practice. DESIGN AND METHODS: Incident case-referent study nested within a population-based health survey. We compared screening models with three risk criteria and calculated sensitivity, specificity, positive (PPV) and negative (NPV) predictive values and attributable proportion. We used fasting plasma glucose (FPG) alone or with an oral glucose tolerance test (OGTT), glycosylated haemoglobin A (HbA1c) (normal range 3.6-5.3%), body mass index (BMI), triglycerides and family history of diabetes (FHD).
SETTING: Participants in a health survey at all primary care centres (n=33,336) and subjects with diagnosed type 2 diabetes in primary and hospital care (n=6088) in Umeå during 1989-2001.
SUBJECTS: Each of the 164 subjects who developed clinically diagnosed type 2 diabetes (median time to diagnosis of 5.4 years) and 304 sex- and age-matched referents without diabetes diagnosis.
RESULTS: Screening models with at least one criterion present had sensitivities of 0.90-0.96, specificities of 0.43-0.57 and PPVs of 8-9%. Combinations of the criteria, FPG>or=6.1 mmol L-1 (capillary plasma), HbA1c>or=4.7% and BMI>or=27 in men and BMI>or=30 in women, had sensitivities, specificities and PPVs of 0.66%, 0.93% and 32%, and 0.52%, 0.97% and 46% respectively. Using FHD as one of three risk criteria showed comparable results. Addition of triglycerides or OGTT did not improve the prediction.
CONCLUSIONS: The combination of HbA1c, FPG and BMI are effective in screening for individuals at risk of future clinical diagnosis of type 2 diabetes. OGTT or FHD is not necessary.