Glycated haemoglobin (HbA1c) and fasting plasma glucose relationships in sea‐level and high‐altitude settings

Aim 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 HbA1c and fasting plasma glucose (FPG) in populations living at sea level and at an altitude of > 3000 m. Methods 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 HbA1c and FPG was assessed using a Kappa index. Results 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
What's new? Haemoglobin levels and differences in glucose metabolism at high altitude may influence the diagnostic performance of testing for diabetes using HbA1c.We found that the relationship between HbA1c and fasting plasma glucose (FPG) differed markedly between high‐altitude and sea‐level areas.The relationship between HbA1c and FPG was quadratic at sea level and linear at high altitude.Corresponding FPG values for an HbA1c ≥ 48 mmol/mol (≥ 6.5%) cut‐off point, used for the diagnosis of diabetes, were 6.6 and 14.8 mmol/l (120 and 266 mg/dl) at sea level and high altitude, respectively.The sensitivity of HbA1c to detect abnormal FPG was 87.3% at sea level and 40.9% at high altitude. This suggests a limitation in the performance of HbA1c to diagnose diabetes at altitude.