Capillary and venous haemoglobin levels in blood donors: a 42-month study of 36 258 paired samples

Background EU law requires a haemoglobin of >= 12 center dot 5 g/dl for women or >= 13 center dot 5 g/dl for men at the time of donation. As capillary and venous haemoglobin values may differ in the same subject, we examined whether a capillary haemoglobin level of 12 center dot 0 g/dl for women or 13 center dot 0 g/dl for men, is equivalent to a venous haemoglobin level of >= 12 center dot 5 g/dl and >= 13 center dot 5 g/dl, respectively, to avoid unnecessary loss of blood donations. Methods Over a continuous 42-month period, 36 258 paired capillary and venous samples were taken from 25 762 females and 10 496 males, when the capillary haemoglobin was < 12 center dot 5 g/dl and < 13 center dot 5 g/dl respectively. Results Venous haemoglobin levels were higher than capillary levels, with a mean difference of 1 center dot 07 g/dl (SD 0 center dot 68 g/dl), range -2 center dot 2 to +3 center dot 25 g/dl for men (P < 0 center dot 001), and a mean difference of 0 center dot 67 g/dl (SD 0 center dot 65 g/dl), range -2 center dot 5 to +5 center dot 4 g/dl for women (P < 0 center dot 001). The difference for the three consecutive winters was 0 center dot 78 g/dl (SD 0 center dot 081 g/dl) for females and 1 center dot 26 g/dl (SD 0 center dot 162 g/dl) for males and for the three consecutive summers was 0 center dot 56 g/dl (SD 0 center dot 089 g/dl) for females and 0 center dot 88 g/dl (SD 0 center dot 134 g/dl) for males: P < 0 center dot 001. Conclusions Capillary haemoglobin levels of 12 center dot 0-12 center dot 5 g/dl in healthy females or 13 center dot 0-13 center dot 5 g/dl in healthy males are substantively equivalent to venous haemoglobin levels of >= 12 center dot 5 and >= 13 center dot 5 g/dl for women and men respectively. This finding has permitted an additional 32 990 blood units to be collected over the period of the study, a gain of 9 center dot 4%.