Ren Q, Lv X, Yang L, et al. - Population-based epidemiological survey was performed to explore A1c performance for diabetes screening in high-altitude polycythemia compared to population with high proportion living in oxygen-deficient environment. They included 1,401 Tibetan individuals (mean age was 44.3 ± 15.0 years) without known diabetes. They included volunteers through educational advertisements about diabetes. They conducted oral glucose tolerance test, hemoglobin A1c (HbA1c), and complete blood cell count. They further investigated HbA1c applying high-performance liquid chromatography, and using the hexokinase method for the evaluation serum glucose level. They applied World Health Organization criteria to characterize diabetes and pre-diabetes. By using receiver operating characteristic analysis, they examined HbA1c test performance. In Tibet, 46 mmol/mol (6.4%) optimal HbA1c cut-off was noted for detection of diabetes. The data indicated RBC count was an independent risk factor for increased HbA1c, and HAPC may influence the predictive ability of HbA1c.