Capillary versus venous haemoglobin determination in the assessment of healthy blood donors
Correspondence: Barbara J. Bryant, MD, University of Texas Medical Branch, Department of Pathology, Blood Bank Division, 301 University Blvd, Route 0717, Galveston, TX 77555-0717, USA
Background and Objectives
To determine the accuracy of fingerstick haemoglobin assessment in blood donors, the performance of a portable haemoglobinometer (HemoCue Hb 201+) was prospectively compared with that of an automated haematology analyzer (Cell-Dyn 4000). Haemoglobin values obtained by the latter were used as the ‘true’ result.
Material and Methods
Capillary fingerstick samples were assayed by HemoCue in 150 donors. Fingerstick samples from two sites, one on each hand, were obtained from a subset of 50 subjects. Concurrent venous samples were tested using both HemoCue and Cell-Dyn devices.
Capillary haemoglobin values (HemoCue) were significantly greater than venous haemoglobin values (HemoCue), which in turn were significantly greater than venous haemoglobin values by Cell-Dyn (mean ± SD: 14·05 ± 1·51, 13·89 ± 1·31, 13·62 ± 1·23, respectively; P < 0·01 for all comparisons among groups). Nine donors (6%) passed haemoglobin screening criteria (≥12·5 g/dl) by capillary HemoCue, but were deferred by Cell-Dyn values (false-pass). Five donors (3%) were deferred by capillary sampling, but passed by Cell-Dyn (false-fail). Substantial variability in repeated fingerstick HemoCue results was seen (mean haemoglobin 13·72 vs. 13·70 g/dl, absolute mean difference between paired samples 0·76 g/dl). Hand dominance was not a factor.
Capillary samples assessed via a portable device yielded higher haemoglobin values than venous samples assessed on an automated analyzer. False-pass and false-fail rates were low and acceptable in the donor screening setting, with ‘true’ values not differing by a clinically significant degree from threshold values used to assess acceptability for blood donation.