Retinol-binding protein stability in dried blood spots.
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 degrees C/7 days, (c) 30 degrees C/14 days, (d) 30 degrees C/28 days, and (e) 4 degrees C/38 days. Baseline RBP concentrations were compared to those obtained after the storage treatments. For the field study, 50 paired DBS and serum specimens were prepared from venous blood obtained in northern Kenya. DBS were stored in a sealed plastic bag with desiccant at ambient temperature (12 degrees C-28 degrees C) for 13-42 days, and sera were stored at -20 degrees C to -70 degrees C. Recovered RBP concentrations were compared with serum retinol for stability, correlation, sensitivity, and specificity.


RESULTS
RBP in DBS stored in the laboratory at 30 degrees C remained stable for 2-4 weeks, but specimens stored at 4 degrees 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.


CONCLUSIONS
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.
Fujita
Masako
M
Department of Anthropology, University of Washington, Seattle, WA 98195-3100, USA. masakof@u.washington.edu
Brindle
Eleanor
E
Shofer
Jane
J
Ndemwa
Philip
P
Kombe
Yeri
Y
Shell-Duncan
Bettina
B
O'Connor
Kathleen A
KA
D001800:Blood Specimen Collection; D005260:Female; D006801:Humans; D007630:Kenya; D009656:North America; D012177:Retinol-Binding Proteins / Q000032:analysis*; D012680:Sensitivity and Specificity; D013696:Temperature; D013997:Time Factors; D014801:Vitamin A / Q000097:blood; D014802:Vitamin A Deficiency / Q000175:diagnosis
D012177:Retinol-Binding Proteins; D014801:Vitamin A