Retinol concentrations in capillary dried blood spots from healthy volunteers: method validation

Background: Vitamin A deficiency (VAD) is a major public health problem in the developing world, leading to >3 million eye-related problems in prescho ol children. Nearly 250 million children have subclinical VAD, resulting in a 23% increase in childhood mortality. Difficulties in obtaining samples t o assess VAD have hampered the detection, intervention, and surveillance of VAD. The use of dried blood spots (DBS) could ameliorate many problems of vitamin A assessment. Objective: The objective of this study was to validate the use of retinol i n DBS for vitamin A assessment by comparing it with venous and capillary se rum retinol. Design: Venous and capillary blood specimens were obtained simultaneously f rom 20 healthy adult volunteers. From each blood specimen, both DBS and Liq uid serum were prepared (a total of 80 samples). All specimens were maintai ned at -70 degrees C until HPLC analysis. Results: The mean retinol concentrations in the 4 sample types were as foll ows: venous serum (2.02 +/- 0.42 mu mol/L, or 58 +/- 12 mu g/dL), capillary serum (2.06 +/- 0.42 mu mol/L, or 59 +/- 12 mu g/dL), venous DBS (2.06 +/- 0.49 mu mol/L, or 59 +/- 14 mu g/dL), and capillary DBS (2.09 +/- 0.45 mu mol/L, or 60 +/- 13 mu g/dL). Of the 6 possible 2-way combinations, the R-2 values ranged from 0.77 for capillary DBS versus venous DBS to 0.95 for ve nous serum versus capillary serum. Conclusions: DBS retinol measured by HPLC is comparable with serum retinol. Thus, it is possible to compare and combine blood retinol concentration da ta obtained from DBS with current and historic measurements in serum.