title: Incidence of type 2 diabetes by HbA1c and OGTT: the Isfahan Diabetes Prevention Study.
abstract: The aim of this study was to estimate the incidence of type 2 diabetes using newly proposed hemoglobin A(1C) (HbA(1c)) and current oral glucose tolerance test (OGTT) definition in an Iranian non-diabetic population. A total of 923 non-diabetic first-degree relatives (FDRs) of patients with type 2 diabetes 30-70 years old in 2003-2005 were followed through 2009 for the occurrence of type 2 diabetes. At baseline and through follow-ups, participants underwent a standard 75 g 2-h OGTT and HbA(1c) measurements. Prediction of progression to type 2 diabetes by OGTT-defined or HbA(1c)-defined diabetes was assessed with area under the receiver operating characteristic (ROC) curves based upon measurement of fasting plasma glucose, 2-h post-load glucose values, and HbA(1c). The prevalence of type 2 diabetes was 9.2% (95% CI: 8.2, 10.2) by OGTT-defined diabetes and 7.9% (95% CI: 6.9, 9.0) by HbA(1c) ≥ 6.5. The incidence of type 2 diabetes was 2.0% (95% CI: 1.6, 2.4) (1.8% men and 2.1% women) per year by the current OGTT definition, whereas the incidence rates were 1.7% (95% CI: 1.3, 2.0) (1.6% men and 1.7% women) per year by HbA(1c) ≥ 6.5%. Of those diagnosed with type 2 diabetes by OGTT, 69.6% had HbA(1c) <6.5% and therefore would not have been classified as having type 2 diabetes. The incidence and prevalence of diabetes using newly proposed HbA(1c) threshold in this FDRs of patients with type 2 diabetes were slightly lower than using current OGTT definition.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran. janghorbani@yahoo.com
authors.forename: Mohsen
authors.initials: M
authors.lastname: Janghorbani
authors.forename: Masoud
authors.initials: M
authors.lastname: Amini
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D015994:Incidence; D007492:Iran / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin