Dried Blood Spot Collection and Elution Procedures for Measurement of Retinol Binding Protein: A Biomarker of Vitamin A Status for Field Research

Eleanor Brindle, University of Washington
Masako Fujita, University of Washington
Dean Garrett, Program for Appropriate Technology in Health (PATH)
Jonathan Gorstein, University of Washington
Bettina Shell-Duncan, University of Washington
Kathleen A. O'Connor, University of Washington

Vitamin A deficiency (VAD) is a serious public health problem in some developing countries. Retinol-binding protein (RBP) measurements in dried blood spots (DBS) are a vital tool for assessment of VA status in field conditions where laboratory facilities are not immediately available. We validate DBS protocols for RBP against serum and plasma measures. Plasma, serum, capillary DBS, and DBS from venous blood with and without anti-coagulant were collected simultaneously (8 participants, ages 25-45) and compared to identify DBS collection and elution protocols yielding RBP results (Scimedx Scanlisa RBP-EIA) most similar to plasma and serum. RBP recovery from DBS specimens averaged 90% of RBP in serum and 94% of RBP in plasma, and varied slightly by elution protocol used. Agreement with serum and plasma results was highest using two 1/8” punches from capillary DBS eluted to a 50-fold dilution. Results were more similar to serum values using proportionally higher elution volumes.