Background: Retinol-binding protein (RBP) is accepted as a surrogate biochemical marker for retinol to determine vitamin A (VA) status. A recently developed enzyme immunoassay for RBP uses serum or whole blood stored as dried blood spots (DBS). However, the stability of RBP in DBS has not been examined.
Methods: RBP stability was studied in a laboratory and in field conditions in northern Kenya. For the laboratory study, 63 DBS collected by finger prick and stored sealed in a plastic bag with desiccant were exposed to 1 of 5 time/storage-temperature treatments: (a) baseline, (b) 30 °C/7 days, (c) 30 °C/14more »
Results: RBP in DBS stored in the laboratory at 30 °C remained stable for 2–4 weeks, but specimens stored at 4 °C for 38 days produced values below baseline (P = 0.001). DBS stored under field conditions remained stable for 2–6 weeks, as demonstrated by good correlation with serum retinol, a result that suggests that RBP in DBS will have good sensitivity and specificity for predicting VA deficiency.
Conclusion: RBP in DBS can withstand storage at a relatively high ambient temperature and thus facilitate accurate VA assessments in populations in locations where serum collection and storage are unfeasible.