Innovative approaches to vitamin A assessment

The health and sight of millions of children are compromised each year as a consequence of vitamin A (VA) deficiency. Serum retinol is the most common ly used indicator of VA status. Unfortunately, its use is impractical for n ational surveys because it involves collection of venous blood, centrifugat ion and frozen storage before analysis. To make VA assessment more practica l, we have developed approaches incorporating dried blood spots (DBS) or po rtable instrumentation. DBS have been used as a sample matrix to screen neo nates for many biochemical compounds. Until recently, it was not thought th at VA was stable in DBS, However, we demonstrated that the measure of DBS r etinol correlates well with serum retinol in both healthy adults (r(2) = 0. 88-0.90) and compromised populations (r(2) = 0.73-0.84). Compared with seru m retinol, the sensitivity and specificity of detecting VA deficiency by DB S retinol range from 73 to 93% and from 90 to 100%, respectively. Although few data are available, retinol binding protein (RBP) can also be measured in DBS. REP has been used as a surrogate marker for serum retinol. Correlat ions coefficients (r(2)) between serum REP and serum retinol range from 0.4 to 0.8. in addition, work has been done to develop portable instrumentatio n to measure VA status in the field. A fluorometer has been optimized for V A fluorescence and is linear into the deficient range for the direct fluori metric measurement of serum holo-RBP. Progress is being made to use the ins trument to directly measure holo-RBP in a drop of whole blood.