Positive Direct Antiglobulin Test due to Antiphospholipid Antibodies in Normal Healthy Blood Donors

Objectives: Positive direct antiglobulin tests (DAT) occur occasionally, without obvious cause, among normal blood donors. This is sometimes associated with a false-positive serologic test for syphilis. Positive DATs due to antiphospholipid antibodies (APAbs) are well documented in the antiphospholipid syndrome with systemic lupus erythematosus and the primary antiphospholipid syndrome. Methods: Using conventional haematologic and serologic methods, we tested 474,545 normal blood donors in the west of Scotland during the years 1991 through 1993. Results: We identified 42 normal blood donors with a positive DAT and observed three who had positive DATs and false-positive VDRL tests,all of whom expressed raised APAbs. Conclusion: APAbs may be an incidental cause of positive DATs among healthy blood donors.