title: Glycated haemoglobin (HbA1c) and fasting plasma glucose relationships in sea-level and high-altitude settings.
abstract: Higher haemoglobin levels and differences in glucose metabolism have been reported among high-altitude residents, which may influence the diagnostic performance of HbA1c. This study explores the relationship between HbA1cand fasting plasma glucose (FPG) in populations living at sea level and at an altitude of > 3000 m.
  
  
  
  Data from 3613 Peruvian adults without a known diagnosis of diabetes from sea-level and high-altitude settings were evaluated. Linear, quadratic and cubic regression models were performed adjusting for potential confounders. Receiver operating characteristic (ROC) curves were constructed and concordance between HbA1cand FPG was assessed using a Kappa index.
  
  
  
  At sea level and high altitude, means were 13.5 and 16.7 g/dl (P > 0.05) for haemoglobin level; 41 and 40 mmol/mol (5.9% and 5.8%; P < 0.01) for HbA1c; and 5.8 and 5.1 mmol/l (105 and 91.3 mg/dl; P < 0.001) for FPG, respectively. The adjusted relationship between HbA1cand FPG was quadratic at sea level and linear at high altitude. Adjusted models showed that, to predict an HbA1cvalue of 48 mmol/mol (6.5%), the corresponding mean FPG values at sea level and high altitude were 6.6 and 14.8 mmol/l (120 and 266 mg/dl), respectively. An HbA1ccut-off of 48 mmol/mol (6.5%) had a sensitivity for high FPG of 87.3% (95% confidence interval (95% CI) 76.5 to 94.4) at sea level and 40.9% (95% CI 20.7 to 63.6) at high altitude.
  
  
  
  The relationship between HbA1cand FPG is less clear at high altitude than at sea level. Caution is warranted when using HbA1cto diagnose diabetes mellitus in this setting.
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: J C
authors.initials: JC
authors.lastname: Bazo-Alvarez
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: R
authors.initials: R
authors.lastname: Quispe
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|University College London Medical School, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: T D
authors.initials: TD
authors.lastname: Pillay
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: A
authors.initials: A
authors.lastname: Bernabé-Ortiz
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: L
authors.initials: L
authors.lastname: Smeeth
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Division of Pulmonary and Critical Care, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: W
authors.initials: W
authors.lastname: Checkley
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Área de Investigación y Desarrollo, A.B. PRISMA, Lima, Peru.|Department of International Health, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: R H
authors.initials: RH
authors.lastname: Gilman
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Department of Medicine, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: G
authors.initials: G
authors.lastname: Málaga
authors.affiliation: CRONICAS Centre of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Department of Medicine, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: J J
authors.identifier: 0000-0002-4738-5468
authors.initials: JJ
authors.lastname: Miranda
mesh_terms: D000328:Adult; D000368:Aged; D000531:Altitude; D001786:Blood Glucose / Q000032:analysis*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000175:diagnosis*; D005215:Fasting / Q000097:blood*; D005260:Female; D005843:Geography; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010568:Peru
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin