Optimising nuclear techniques to assess vitamin A status in population surveys – from deficiency to excess (Phase II)

Vitamin A deficiency (VAD) remains a leading cause of childhood blindness and is a major contributor to infectious disease morbidity and mortality among pre-school children. As a response to the population risk, supplementation as well as fortification with vitamin A (VA) are in place in many low-income countries, but unfortunately there is rarely any coordination to avoid overlap of interventions or to monitor long-term effects. Despite VA deficiency still being widespread in some communities, there are concerns about inadvertent chronic excessive VA intakes in other population groups.
Serum retinol is widely used as a biomarker for VAD, but due to its tight homeostatic control, it cannot reflect changes in status when VA stores are adequate or excessive. Assessment of population VA status and evaluation of VA programmes require a biomarker that can estimate risk of VA deficiency as well as excess. The retinol isotope dilution (RID) technique, a nuclear technique, is the only method that can quantitatively measure VA status over the entire spectrum from deficiency to excess without the need for a liver biopsy.
The priorities for the proposed CRP are to optimise the RID for use in population surveys and to further optimise the field procedures, calculations, and interpretations for use by non-experts. This will support the monitoring of vitamin A programmes in the context of a dual risk of VA malnutrition - deficiency as well as excess.
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