Extreme Variability of Anemia Prevalence in Peruvian Children Based on Different Altitude Correction Factors: A Cross-Sectional Study.

Baquerizo-Sedano, Luis, José Augusto Chaquila, Juan Pablo Aparco, Carlos Torres Salinas, Orison O Woolcott, and Pedro González-Muniesa. Extreme variability of anemia prevalence in peruvian children based on different altitude correction factors: A cross-sectional study. High Alt Med Biol. 00:00-00, 2025. Objetives: Higher erythrocytosis is the main hematological adaptation to altitude. Consequently, several correction factors have been proposed to diagnose anemia in children at high altitude. We compared the anemia prevalence in Peruvian children aged 6-59 months living at different altitudes according to several published correction factors to adjust hemoglobin for altitude. Methods: Data were collected from 578,576 children in the Nutritional Surveillance System in Peru in 2020. Anemia prevalence was estimated by altitude every 1,000 m, using four different adjustment criteria, including the recent adjustment proposal from the World Health Organization. Results: The total prevalence of anemia varied substantially (from 3.2% to 33.7%) depending on the adjustment criteria used. Without correction factors, the highest proportion of anemia was observed in the lowest altitude range. However, this result was no longer observed when the adjustment factors were used. For ranges above 3,000 m, moderate anemia occurred with a higher prevalence when using two different correction factors but not others or without adjustment. Conclusions: Our findings reveal substantial changes in anemia prevalence among Peruvian children under 5 years of age depending on the adjustment factors for hemoglobin used. More research is needed to properly diagnose anemia in children at high elevations.