LAUSR

some clinicians may apply independent criteria to diagnose anemia or may apply tailored criteria based on patient-specific factors. Further work is urgently required to clarify, establish and harmonize hemoglobin thresholds to diagnose anemia. As well as statistical definitions, thresholds may need to consider where adverse functional clinical (e.g., fatigue), or developmental (e.g., cognitive development in children) outcomes are seen; or where investigation is essential to exclude underlying diseases. WHO has established a programme of work to review hemoglobin thresholds used to define anemia. An online expert consultation identified priority areas including variations in thresholds by sex and age, definitions of anemia severity, adjustments of definitions by elevation above sea level, and hemoglobin concentrations associated with adverse developmental outcomes in infants and birth outcomes in mothers. Definitive studies characterizing the hemoglobin thresholds that define anemia across populations, ages and ethnicities, with correlation to clinical and functional outcomes, are essential to enable harmonization in interpretation of this crucial biomarker.