Problems associated with the presence of immunofluorescent heterophile antibody in sera submitted for autoantibody screening.

A small proportion of sera submitted for routine immunofluorescent antibody screening contains heterophile antibodies. The reaction patterns produced by the heterophile antibody may be confused with or mask specific autoantibody patterns, leading to false positive or false negative autoantibody results. In this study we report the development of a method in which fresh sheep red cells are used to absorb heterophile antibody from sera without affecting specific autoantibody which may be present. This technique was used on a panel of 142 sera known to contain heterophile antibody but not initially reported as containing specific autoantibodies by immunofluorescence. After absorption with sheep red cells the heterophile antibody was completely removed from the sera under test and 27 (19%) specimens were shown to contain previously undetected autoantibodies. Only 6 (4%) of the sera, however, contained autoantibodies at a titre which would be reported as a positive result on routine screening. These results suggest that there may be a significant number of sera submitted for routine autoantibody screening which contain autoantibodies that are masked by the presence of heterophile antibody. Selective use of the absorption technique offers a simple solution to this problem.