The VDRL test in a blood transfusion service.

A survey has been made of the results of 12 months' VDRL screening in a blood transfusion service. Positive VDRL tests were found on 318 of the 73 350 blood donations collected during 1974. Thirty-four tests confirming specific treponemal infection were found in 24 donors. A battery of confirmatory tests showed the remaining 284 positive VDRL reactions from 235 donors to be biological false positive (BFP) results, and, of these, one-third were considered entirely negative by the reference laboratory. BFP reactions were commoner in female donors than in males, and a higher incidence than expected was observed in younger female donors and older male donors. A marked seasonal incidence was noted, 65% of all BFP tests from the transfusion service being found in the four colder months of May to August. Although some differences exist between the group as a whole and the 36 donors (15.3%) found to have BFP results on more than one occasion during the year, there is little evidence from these studies to suggest that regular blood donation per se is a contributing factor to the finding of a BFP result in VDRL screening. It is probable that the population tested regularly by the blood transfusion service reflects a small but representative sample of the community as a whole.