title: Is HbA1c a good screening test for diabetes mellitus?
abstract: OBJECTIVE
  HbA(1c) has been recently recommended as the primary diagnostic test for diabetes. This study evaluated the positive predictive value (PPV) and negative predictive value (NPV) of HbA(1c) against the oral glucose tolerance test (OGTT) in three locations.
  
  
  METHODS
  Three years of data with concurrent OGTT and HbA(1c) tests were extracted from Laboratory Information Systems (LIS) and receiver operator (ROC) curves and positive and negative predictive values calculated comparing the OGTT with the HbA(1c) values using a 10% prevalence of diabetes.
  
  
  RESULTS
  The recommended threshold HbA(1c) value of 6.5% did not give the optimal combination of NPV (0.93 to 0.92) and PPV (0.40 to 0.61) compared to a threshold HbA(1c) value of 7.0% (NPV 0.91 to 0.92, PPV 0.61 to 0.73).
  
  
  CONCLUSIONS
  The optimal HbA(1c) value for the diagnosis of diabetes is 7.0% but even at this HbA(1c) the PPV is suboptimal and may cause up to 12% of patients without diabetes, as defined by a normal OGTT, to be classified having diabetes mellitus.
authors.affiliation: DynaLIFEDx, Edmonton, Alberta, Canada. Trefor.higgins@dynalifedx.com
authors.forename: Trefor N
authors.initials: TN
authors.lastname: Higgins
authors.forename: David
authors.initials: D
authors.lastname: Tran
authors.forename: George S
authors.initials: GS
authors.lastname: Cembrowski
authors.forename: Carol
authors.initials: C
authors.lastname: Shalapay
authors.forename: Pamela
authors.initials: P
authors.lastname: Steele
authors.forename: Carmen
authors.initials: C
authors.lastname: Wiley
mesh_terms: D000328:Adult; D000368:Aged; D003920:Diabetes Mellitus / Q000097:blood / Q000175:diagnosis*; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve
chemical_list: D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human