[Undiagnosed diabetes and impaired glucose metabolism on high risk Spanish population. The IGT study]

To estimate the prevalence of undiagnosed diabetes and impaired glucose metabolism on high risk Spanish population, contrasting phenotypic features according to both sets of criteria, World Health Organization (WHO) and American Diabetes Association (ADA).

Cross-sectional, multicentre (10 health-care centres, 230,000 inhabitants), selective risk-factor study. WHO diagnoses (normal, impaired glucose tolerance [IGT] and diabetes) were based on the 2 h plasma glucose (2hPG) following a 75 g oral glucose tolerance test (OGTT) and ADA diagnoses according the fasting plasma glucose (FPG) (normal, impaired FPG and diabetes). Prevalence, diagnostic overlap index and 22 clinical and biological parameters were compared.

The study included 580 subjects (330 women), mean age 58.1 years and body mass index 31.2 kg/m2, 292 (50.3%) with only one risk factor and 288 (49.7%) with two or more risk factors. WHO diagnoses were: 291 (50.2%) normal glucose tolerance (95% CI: 46.2-54.2%), 157 (27.1%) IGT (23.5-30.7%) and 132 (22.7%) diabetes (19.3-26.1%). ADA diagnoses were: 355 (61.2%) normal FPG (57.2-65.2%), 146 (25.2%) IFG (21.7-28.7%) and 79 (13.6%) diabetes (10.9-16.3%). The prevalence of diabetes decreased 9.1% (from -11.4 to -6.8%). The diagnostic overlap was 33.5% for diabetes and 19.3% for impaired glucose homeostasis (IGT-FPG). Omitting the OGTT half the diabetic subjects with 2hPG > or = 200 mg/dl (11.1 mM) but FPG < 126 mg/dl (7 mM) would remain undiagnosed. By changing screening criteria (FPG instead of 2hPG) the risk related to traditional factors such as age or a first-degree relative with diabetes would reduce.

Applying ADA criteria, the high prevalence of undiagnosed glucose abnormalities would decrease. These results suggest that it is strongly advisable the continued use of the 2hPG for diabetes screening on high risk Spanish population.