WHO Hemoglobin Thresholds to Define Anemia in Clinical Medicine and Public Health: A Scoping Exercise

Abstract

Abstract Objectives WHO is reviewing the use and interpretation of hemoglobin thresholds for assessing iron status in individuals and populations following established evidence-informed guideline development procedures to culminate in updated guidelines for clinical and public health use. Methods To define priorities and identify key questions a scoping exercise was developed via a two-stage international consultation based on the Child Health and Nutrition Research Initiative method. The first survey allowed respondents to suggest priorities, and the second asked respondents to rank the key questions with established criteria. A transparent approach was used to identify more than 4000 international experts in anemia research based on publication records and ensuring representatives from all WHO regions and low income and middle-income countries. Results The first survey received 123 respondents from 48 countries across all six WHO regions. The 553 proposed questions spanned many themes and were consolidated to a shortlist of 48 questions spanning six subtopics, including physiology of anemia, hemoglobin thresholds for different population groups, definition of anemia across clinical and environmental contexts, approach to development of anemia thresholds, laboratory and diagnostic considerations, and implementation of WHO's hemoglobin threshold guidelines. The second survey received 195 respondents from 64 countries across all six WHO regions. Questions covered diverse themes, including variation in thresholds between individuals of different sex and age, categorisation of anaemia severity and the burden of anaemia, optimal clinical and field laboratory measurements of haemoglobin, and antenatal and infant haemoglobin concentrations associated with adverse developmental outcomes. Conclusions Based on the normative needs identified in this scoping exercise the available evidence will be summarized and presented to a WHO guideline development group after input from an expert panel. This rigorous, inclusive, and transparent approach should enable international harmonization of hemoglobin thresholds used to define anemia in both clinical and public health practice. Funding Sources The World Health Organization The United States Agency for International Development (USAID), USA Centers for Disease Control and Prevention (CDC), USA.