BACKGROUND: Both donors and the blood bank rely on the result of the donor health interview. However, survey data suggest that substantial variability in deferral rates among interviewers exist. We studied whether variability remained after adjusting for conditional factors. STUDY DESIGN AND METHODS: The data set included Dutch interview data on whole blood donor visits in 2015, where one of their visits was selected randomly. We applied logistic regression and multilevel regression analyses with the donor visit, with the interviewer representing the levels. We set up four models: 1) all reasons deferral, 2) low-hemoglobin-level deferral, 3) infectious disease risk deferral and 4) other medical reasons deferral. RESULTS: In total, 138,398 visits were included in the study, of which 60,534 (43.7%) related to male donors. The overall deferral rate for men was 7.91% and for women 12.25%. Deferral rates among interviewers ranged from as low as 1.19% up to 28.8%. Models 2 (low hemoglobin level) and particularly 4 (other medical reasons), for both men and women, showed significant intraclass correlation coefficients, implying considerable deferral rate variability among interviewers. Donor age, the number of previous visits, and the season had relatively large effects. However, explained variances of the logistic regression models were relatively low, ranging from 2.53% to 7.35%. CONCLUSION: Deferral appears to be a random process, while substantial variability was found among interviewer deferral rates, suggesting that some interviewers are more cautious than others. Our results suggest heuristic and subjective diagnosing to be prevalent. Steps should be taken to improve interview result validity.