title: HbA1c in the diagnosis of diabetes and abnormal glucose tolerance in patients with Graves' hyperthyroidism.
abstract: OBJECTIVE
  To assess the suitability of HbA1c as a criterion for the diagnosis of diabetes in patients with Graves' disease.
  
  
  METHODS
  This study enrolled 310 patients with untreated newly diagnosed Graves' disease, 208 patients with euthyroid goiter and 329 age-matched (control) subjects without thyroid disease from Fuzhou, China. The performance of HbA1c against the OGTT for diagnosing diabetes was determined. The Framingham risk score was used to assess general cardiovascular disease (CVD) risk.
  
  
  RESULTS
  The percentage of patients with abnormal glucose metabolism as classified by HbA1c levels was lower than by OGTT criteria in patients with Graves' disease-33.2% vs. 41.3% for pre-diabetes and 4.5% vs. 11.3% for diabetes, respectively. The sensitivity of HbA1c for diagnosing diabetes in patients with Graves' disease was lower than in patients with euthyroid goiter and subjects without thyroid disease (34.9%, 63.2% and 60.6% respectively), while the specificity was similar (99.3%, 98.6%, 97.4%). Approximately 7.4% of patients with Graves' disease diagnosed with diabetes according to OGTT criteria were misdiagnosed as not having the disease by HbA1c, much higher than that for the other two groups. Patients with Graves' disease with diabetes not diagnosed with the disease by HbA1c showed a high risk for CVD.
  
  
  CONCLUSIONS
  The low sensitivity of the HbA1c criterion underestimated the percentage of diabetes in patients with Graves' disease. Patients with diabetes who were misdiagnosed as not having the disease by HbA1c were at high risk for CVD.
authors.affiliation: Endocrinology Department, The First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, Fujian, China. Electronic address: liyongy@yahoo.com.
authors.forename: Liyong
authors.initials: L
authors.lastname: Yang
authors.affiliation: Endocrinology Department, The First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, Fujian, China.
authors.forename: Ximei
authors.initials: X
authors.lastname: Shen
authors.affiliation: Endocrinology Department, The First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, Fujian, China.
authors.forename: Sunjie
authors.initials: S
authors.lastname: Yan
authors.affiliation: Endocrinology Department, The First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, Fujian, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Endocrinology Department, The First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, Fujian, China.
authors.forename: Juanjuan
authors.initials: J
authors.lastname: Lu
authors.affiliation: Endocrinology Department, The First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, Fujian, China.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Wei
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis; D001786:Blood Glucose / Q000378:metabolism*; D016022:Case-Control Studies; D002681:China; D003920:Diabetes Mellitus / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D018149:Glucose Intolerance / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D006442:Glycated Hemoglobin / Q000032:analysis*; D006111:Graves Disease / Q000150:complications* / Q000503:physiopathology; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D011379:Prognosis; D055815:Young Adult
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human