title: Low positive predictive value of hemoglobin A1c for diagnosis of prediabetes in clinical practice.
abstract: BACKGROUND
  Positive predictive value (PPV) of hemoglobin A1c (HbA1c) for diagnosis of prediabetes in clinical practice has not been well studied.
  
  
  METHODS
  In a prospective study, patients diagnosed with prediabetes based on HbA1c (5.7%-6.4%) underwent a 75-g oral glucose tolerance test (OGTT) as the gold standard test to diagnose dysglycemia. Demographics, anthropometrics, comorbidity, concomitant prescription medications and biochemical data were collected.
  
  
  RESULTS
  We identified 66 patients with HbA1c-based prediabetes with a mean HbA1c of 6.00 ± 0.20%. However, based on the OGTT, 32 had normal glucose tolerance (NGT), 26 had prediabetes and 8 had diabetes yielding a PPV of HbA1c of 39.4%. In univariate analysis, the patients with the OGTT-based prediabetes administered more medications for associated medical problems compared with the NGT group (5.9 ± 2.2 versus 2.6 ± 1.8, P < 0.0001). After adjustment for baseline variables, the medication use remained significantly different between OGTT-based prediabetes and NGT groups (P = 0.041).
  
  
  CONCLUSIONS
  PPV of HbA1c for diagnosis of prediabetes in clinical setting is low. Patients with HbA1c of 5.7% to 6.4% should undergo OGTT to confirm diagnosis of dysglycemia.
authors.affiliation: Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine (ARG), University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Preventive Medicine (JW), University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: Aidar R
authors.initials: AR
authors.lastname: Gosmanov
authors.forename: Jim
authors.initials: J
authors.lastname: Wan
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D003430:Cross-Sectional Studies; D005260:Female; D005951:Glucose Tolerance Test / Q000592:standards; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood* / Q000175:diagnosis*; D011237:Predictive Value of Tests; D011446:Prospective Studies
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human