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 preschool children. Nearly 250 million children have subclinical VAD, resulting in a 23% increase in childhood mortality. Difficulties in obtaining samples to 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 in DBS for vitamin A assessment by comparing it with venous and capillary serum retinol. DESIGN: Venous and capillary blood specimens were obtained simultaneously from 20 healthy adult volunteers. From each blood specimen, both DBS and liquid serum were prepared (a total of 80 samples). All specimens were maintained at -70 degrees C until HPLC analysis. RESULTS: The mean retinol concentrations in the 4 sample types were as follows: venous serum (2.02 +/- 0.42 micromol/L, or 58 +/- 12 microg/dL), capillary serum (2.06 +/- 0.42 micromol/L, or 59 +/- 12 microg/dL), venous DBS (2.06 +/- 0.49 micromol/L, or 59 +/- 14 microg/dL), and capillary DBS (2.09 +/- 0.45 micromol/L, or 60 +/- 13 microg/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 venous 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 data obtained from DBS with current and historic measurements in serum.