Application of retinol-binding protein enzyme immunoassay to dried blood spots to assess vitamin A deficiency in a population-based survey: the Uganda Demographic and Health Survey 2006.

BACKGROUND: Vitamin A deficiency is a public health problem in most developing countries. The technological challenges associated with the measurement of serum retinol have limited the epidemiologic assessment of vitamin A deficiency. The combination of retinol-binding protein (RBP) enzyme immunoassay and dried blood spots offers a rapid, inexpensive, and reliable tool for the population-level assessment of vitamin A deficiency in resource-poor settings.
OBJECTIVE: To report on the application of RBP enzyme immunoassay and dried blood spots to assess serum retinol concentrations as an indicator of vitamin A status in the Uganda Demographic and Health Survey 2006.
METHODS: A total of 5,642 capillary blood spot samples were collected by fingerprick onto filter paper cards from women (15-49 years) and children (6-59 months) in a representative probability sample of 9,864 households between May and October 2006. The cards were dried, packed individually with desiccant, and kept at 4 degrees C in a portable refrigerator in the field and at -20 degrees C in the laboratory. Prior to analysis, the RBP enzyme immunoassay was optimized with the use of matched serum and dried blood spots.
RESULTS: The correlation between RBP values determined by matching serum and dried blood spots was excellent (r = 0.79, p < .00001). The prevalence of vitamin A deficiency in women (RBP < 1.24 micromol/L) and children (RBP < 0.825 micromol/L) was 19.4% and 20.4%, respectively.
CONCLUSIONS: The combination of RBP enzyme immunoassay and dried blood spots is a simple, reliable, and cost-effective tool for the estimation of vitamin A deficiency in population-level surveys in resource-poor settings.