Bias and Random Error in Retinol Measurements of Laboratories in Countries with Populations with Mild to Severe Vitamin A Deficiency (Technical Briefs‪)‬

Vitamin A deficiency is common in many developing countries. Population-based surveys suggest that as many as 175 million children of preschool age are vitamin A-deficient (1). Especially in sub-Saharan Africa, severe subclinical deficiency (retinol values [less than or equal to] 0.70 [micro]mol/L) often exceeds 30%. In these countries, laboratories should be able to measure the biochemical indicators of nutritional status to acceptable standards. The aim of the present study was to determine the proficiency of selected laboratories, particularly in Africa, in measuring retinol in serum. The study was performed between September 1999 and February 2000. Laboratories in Africa with the capability to measure vitamin A in serum were located with help from WHO headquarters and country offices, UNICEF headquarters, and through our contacts. Sixteen of the 35 invited laboratories were able to participate in the study: 12 within Africa [in Ethiopia, South Africa (4 laboratories), Tanzania, Zambia, Gabon, Ghana, Nigeria, Egypt, and Morocco], and 4 outside Africa [in Guatemala, Indonesia (2 laboratories), and Vietnam]. Participants were offered a total honorarium of US $200. All laboratories claimed that they could measure retinol in serum. The prevalence of subclinical vitamin A deficiency among preschool children in these countries is 30-40% (2).