Aims/hypothesis: In November 2003 the American Diabetes Association expert committee on the diagnosis and classification of diabetes mellitus suggested a revision of the diagnostic criteria for IFG, lowering the diagnostic threshold from 6.1 to 5.6 mmol/l. The aim of the present study was to evaluate the consequences of this change with respect to: (i) the prevalence of IFG in five different countries; (ii) the concordance between IFG and IGT (classification of individuals); and (iii) the cardiovascular risk profile of these groups. Finally we discuss the likelihood that intervention for cardiovascular risk and prevention strategies developed for individuals with IGT are applicable to subjects with IFG.
Methods: The first part of the study is based on the population-based Danish Inter99 study, where 6265 individuals, aged 30 to 60 years and without previously diagnosed diabetes, underwent an oral glucose tolerance test. The second part is based on the DETECT-2 project, in which studies from China, India, France and USA were used to analyse the impact of the proposed revision of the diagnostic criteria in different ethnic groups.
Results: The proposed change in diagnostic criteria would increase the prevalence of IFG in Denmark from 11.8 to 37.6%. The proposed IFG category would identify 60.0% of all subjects with IGT compared to 29.2% with the old criteria, but among individuals with the new IFG category only 18.5% would also have IGT. Individuals with isolated IFG had lower insulin levels and a lower cardiovascular risk profile with the proposed criteria compared with the current WHO criteria. Data from the DETECT-2 study confirmed the marked increase in the prevalence of IFG, and the estimated number of individuals in the age range 40 to 64 years with IFG in urban India, urban China and the USA would increase by 78%, 135% and 193% respectively.
Conclusions/interpretation: The proposed revised diagnostic criteria will lead to a dramatic increase in the prevalence of IFG, but the concordance rate between IFG and IGT remains low. This new IFG group will have a more favourable cardiovascular risk profile than the current IFG group as defined by the WHO. This seriously questions whether the existing intervention strategies are applicable to the new category of individuals with IFG.