title: Limitations of hemoglobin A1c for the diagnosis of posttransplant diabetes mellitus.
abstract: BACKGROUND
  Posttransplant diabetes mellitus (PTDM) is usually detected 2 to 3 months after transplantation by fasting plasma glucose (fPG) ≥ 7.0 mmol/L (≥ 126 mg/dL) and/or 2 hr post-challenge plasma glucose ≥ 11.1 mmol/L (≥ 200 mg/dL) during an oral glucose tolerance test (OGTT). Recently, glycosylated hemoglobin (HbA1c) of 6.5% or higher (≥ 47.5 mmol/mol) has been proposed as an alternative diagnostic criterion (the HbA1c criterion). We aimed to assess the sensitivity of applying the HbA1c criterion alone or in combination with a single measurement of fPG of 7.0 mmol/L or higher (≥ 126 mg/dL) at 10 weeks after transplantation as screening tests for the diagnosis of PTDM.
  
  
  METHODS
  From 1999 to 2011, measurements of fPG, HbA1c, and OGTT were performed in 1,619 nondiabetic renal transplant recipients.
  
  
  RESULTS
  The HbA1c criterion detected 38.0% of patients with PTDM diagnosed with the standard diagnostic criteria. The specificity was 86.3%. When the HbA1c threshold value was lowered to 6.2% (44.3 mmol/mol), sensitivity increased to 57.8% with a corresponding reduced specificity of 80.4%. A combination of the HbA1c criterion and fPG of 7.0 mmol/L or higher (126 mg/dL) at 10 weeks after transplantation improved diagnostic precision with a sensitivity of 77.7% and a specificity of 96.1%.
  
  
  CONCLUSIONS
  The proposed diagnostic HbA1c criterion failed to detect most cases of PTDM, and one of four cases of PTDM was detected by OGTT alone. This indicates that the HbA1c threshold value likely needs to be lowered for renal transplant recipients and supports continued use of OGTT as a diagnostic tool for detection of PTDM.
authors.affiliation: 1 Department of Transplant Medicine, Section of Nephrology, Oslo University Hospital, Rikshospitalet, Norway. 2 Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Norway. 3 Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Norway. 4 Metabolic and Renal Research Group, UiT, The Arctic University of Norway, Tromsø, Norway.
authors.forename: Ivar Anders
authors.initials: IA
authors.lastname: Eide
authors.forename: Thea Anine Strøm
authors.initials: TA
authors.lastname: Halden
authors.forename: Anders
authors.initials: A
authors.lastname: Hartmann
authors.forename: Anders
authors.initials: A
authors.lastname: Åsberg
authors.forename: Dag Olav
authors.initials: DO
authors.lastname: Dahle
authors.forename: Anna V
authors.initials: AV
authors.lastname: Reisæter
authors.forename: Trond
authors.initials: T
authors.lastname: Jenssen
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000737:chemistry; D048909:Diabetes Complications / Q000097:blood; D003920:Diabetes Mellitus / Q000097:blood / Q000175:diagnosis*; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; D007166:Immunosuppressive Agents