Frequency and specificities of antiphospholipid antibodies (aPL) in volunteer blood donors.

In the State of Indiana, blood donors are screened by a written questionnaire prior to donation to identify potential exposures to infectious diseases and to assess medications. The potential donor is not asked about aPL-related events. Animal experiments have shown, however, that passive transfer of aPL can produce aPL-associated pathology in the recipient. We determined the incidence of antiphospholipid antibodies (aPL) in 775 volunteer blood donors in Indiana. Tubing segments containing 2 ml of anticoagulated blood were obtained from donor units. The average donor age was 43 years (range 17-82); 45% were female. Our in-house aPL ELISA tested for IgG, IgA and IgM to cardiolipin (aCL), phosphatidylserine (aPS), phosphatidylethanolamine (aPE) and phosphatidylcholine (aPC). The plasmas were tested with and without supplemental phospholipid (PL)-binding plasma proteins from adult bovine plasma (ABP). A total of 24 tests were performed for each donor. Normal ranges were determined for 98% of the donors by calculating multiples of the means (MoM) of OD values for each antigen-isotype combination. No decimals were used, all MoMs were rounded up to the next whole number. An additional two MoMs were added to the calculated cutoff values to eliminate borderline positive values. Results revealed that 63 (8.1 %) donors had positive findings for one or more aPL. The relatively high number of aPL-positive individuals reflects the observation that different donors were often in the highest 2% of each antigen-isotype combination tested. The aPL specificities, isotypes, and PL-binding protein dependence are summarized in this report.