title: Relationship between glycated hemoglobin and glucose concentrations in the adult Galician population: selection of optimal glycated hemoglobin cut-off points as a diagnostic tool of diabetes mellitus.
abstract: OBJECTIVE
  To analyze the relationship between glucose and glycated hemoglobin (HbA(1c)) in the adult Galician population, evaluate the use of HbA(1c) for the screening and diagnosis of diabetes, and calculate the diagnostic threshold required for this purpose.
  
  
  METHODS
  We analyzed data on 2848 subjects (aged 18-85 years) drawn from a study undertaken in 2004 to assess the prevalence of diabetes in Galicia. For study purposes, diabetes was defined using the criteria recommended in 2002. Participants were classified into four glucose-based groups. The relationship between glucose and HbA(1c) was described using linear regression models, generalized additive models and Spearman's correlation. Diagnostic capacity was assessed, and optimal HbA(1c) cut-off points were calculated as a diabetes marker using the receiver operating characteristic curve.
  
  
  RESULTS
  Prevalence of pre-diabetes, unknown diabetes and known diabetes was 20.86, 3.37 and 4.39%, respectively. The correlations between HbA(1c) and fasting glucose were higher than those obtained for HbA(1c) and glycemia at 2h of the oral glucose overload (0.344 and 0.270, respectively). Taking glucose levels as the gold standard, a greater discriminatory capacity was obtained for HbA(1c) (area under de cruve: 0.839, 95% confidence intervals: 0.788-0.890). Based on the study criteria, the optimal minimum and maximum HbA(1c) values were 5.9% and 6.7%, respectively.
  
  
  CONCLUSIONS
  HbA(1c) did not prove superior to glycemia for diagnosis of diabetes in the adult Galician population, and cannot therefore be used to replace the oral glucose tolerance test for screening and diagnosis purposes. Indeed, determination of glucose is essential to verify the diagnosis in the majority of cases.
authors.affiliation: Endocrine Section, Hospital Lucus Augusti, Lugo, Spain. manuel.antonio.botana.lopez@sergas.es
authors.forename: Manuel Antonio
authors.initials: MA
authors.lastname: Botana López
authors.forename: Mónica
authors.initials: M
authors.lastname: López Ratón
authors.forename: María Ausencia
authors.initials: MA
authors.lastname: Tomé
authors.forename: Alexis
authors.initials: A
authors.lastname: Fernández Mariño
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Mato Mato
authors.forename: Antonia
authors.initials: A
authors.lastname: Rego Iraeta
authors.forename: Román
authors.initials: R
authors.lastname: Pérez Fernández
authors.forename: Carmen
authors.initials: C
authors.lastname: Cadarso Suárez
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001786:Blood Glucose / Q000032:analysis*; D003920:Diabetes Mellitus / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D013030:Spain / Q000453:epidemiology; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin