Background: Safe blood donation depends upon reliable predonation Hct screening. Earstick (ES) capillary samples are frequently used, but they may not be accurate.
Study design and methods: Predonation ES and fingerstick (FS) and postdonation venous Hct results were compared in 1960 whole-blood and 210 apheresis donors. The validity of using postdonation venous samples to evaluate predonation ES and FS Hct was assessed in 20 whole-blood donors. The impact of Hct screening method on donor Hct deferrals was examined during periods when either ES or FS sampling was used exclusively.
Results: All donors were eligible to donate on the basis of a predonation capillary Hct of > or = 38 percent. In venous samples obtained immediately after donation, 36 percent of whole-blood donors had a Hct <38 percent. With correction for a decrease of approximately 2 Hct units during donation, 20 percent of these donors had a predonation Hct <38 percent. The lowest venous Hct was 23.1 percent. FS samples showed better correlation with venous Hct. Hct discrepancies were similar for apheresis donors. Hct deferrals were significantly higher with FS sampling, especially among women.
Conclusion: Hct determinations from ES samples overestimate venous Hct. Fingerstick samples are more sensitive in detecting anemia. The accuracy of predonation Hct sampling has implications for donor safety, eligibility, and deferral rates.