Evaluation of patients with positive direct antiglobulin tests and nonreactive eluates discovered during pretransfusion testing.

Charts from a series of 679 hospital patients with positive direct antiglobulin tests (DATs) were reviewed. Sixty-three adult patients who demonstrated positive DATs due to IgG only but with nonreactive eluates were selected for further retrospective evaluation. Those patients were noted to fall into four distinct categories: autoimmune diseases including SLE, renal diseases, multiple myeloma, and miscellaneous diseases. In 16 patients for whom serum IgG levels were available, a significant correlation existed between the strength of the DAT reaction and the serum IgG concentration. Several mechanisms that could be responsible for these findings are discussed.