title: Follow-up duration influences the relative importance of OGTT and optimal timing of glucose measurements for predicting future type 2 diabetes.
abstract: OBJECTIVE
  To examine the impact of follow-up duration on the incremental prognostic yield of a baseline oral glucose tolerance test (OGTT) for predicting type 2 diabetes and to assess the discrimination ability of blood glucose (BG) obtained at different time points during OGTT.
  
  
  METHODS
  A prospective, population-based cohort study (Malmö Preventive Project) with inclusion of subjects from 1974 to 1992.
  
  
  METHODS
  A total of 5256 men without diabetes, who had BG measured at 0, 20, 40, 60, 90, and 120 min during OGTT (30 g/m2 glucose), were followed for 30 years. Incident type 2 diabetes was recorded using registries. The performance of OGTT added to a clinical prediction model (age, body mass index (BMI), diastolic blood pressure, fasting BG, triglycerides, and family history of diabetes) was assessed using Harrell's concordance index (C-index) and integrated discrimination improvement (IDI).
  
  
  RESULTS
  Median age was 48 years, mean BMI 24.9 kg/m2, and mean fasting BG 4.7 mmol/L. Models with added post-load BG performed better than the clinical model (C-index: P = 0.08 for BG at 120 min at 5 years, otherwise P ≤ 0.045; IDI: P ≥ 0.06 for BG at 60 and 90 min at 5 years, otherwise P ≤ 0.01). With a longer follow-up duration, C-index decreased, and the C-index increase associated with OGTT was attenuated. Models including BG at 60 or 90 min performed significantly better than the model with BG at 120 min, evident beyond follow-up of 10 and 5 years, respectively.
  
  
  CONCLUSIONS
  OGTT provided incremental prognostic yield for type 2 diabetes prediction. BG measured at 60 or 90 min provided better discrimination than BG at 120 min.
authors.affiliation: Cardiovascular and Metabolic Preventive ClinicDepartment of Endocrinology, Centre for Individualized Medicine in Arterial Diseases (CIMA), Odense University Hospital, Odense, Denmark.
authors.forename: Mette Lundgren
authors.initials: ML
authors.lastname: Nielsen
authors.affiliation: Cardiovascular and Metabolic Preventive ClinicDepartment of Endocrinology, Centre for Individualized Medicine in Arterial Diseases (CIMA), Odense University Hospital, Odense, Denmark.
authors.forename: Manan
authors.initials: M
authors.lastname: Pareek
authors.affiliation: Department of CardiologySkåne University Hospital, Malmö, Sweden.
authors.forename: Margrét
authors.initials: M
authors.lastname: Leósdóttir
authors.affiliation: Department of EndocrinologyOdense University Hospital, Odense, Denmark Section of Molecular Diabetes & MetabolismInstitute of Molecular Medicine & Institute of Clinical Research, University of Southern Denmark, Odense, Denmark.
authors.forename: Kurt
authors.initials: K
authors.lastname: Højlund
authors.affiliation: Department of Clinical SciencesVascular Diseases, Lund University, Malmö, Sweden.
authors.forename: Karl-Fredrik
authors.initials: KF
authors.lastname: Eriksson
authors.affiliation: Department of Clinical SciencesLund University, Skåne University Hospital, Malmö, Sweden.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Nilsson
authors.affiliation: Cardiovascular and Metabolic Preventive ClinicDepartment of Endocrinology, Centre for Individualized Medicine in Arterial Diseases (CIMA), Odense University Hospital, Odense, Denmark Hypertension in Africa Research Team (HART)North-West University, Potchefstroom, South Africa.
authors.forename: Michael Hecht
authors.initials: MH
authors.lastname: Olsen
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis*; D005951:Glucose Tolerance Test; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis
chemical_list: D001786:Blood Glucose