title: Positive direct antiglobulin tests in myeloma patients. Occurrence, characterization, and significance.
abstract: Review of direct antiglobulin testing (DAT) in 88 patients with multiple myeloma (MM) and five with Waldenstrom's macroglobulinemia revealed 26 cases with a positive DAT. Twenty-two of these had immunoglobulin G-M protein, three had light chain MM, and one had immunoglobulin A-MM protein. None of the immunoglobulin GD-MM (n = 2), nonsecretory MM (n = 5), or Waldenstrom's macroglobulinemia patients (n = 5) were positive. None of the patients had hemolysis attributable to the adsorption of the M protein. The serum concentration of M protein was higher in DAT-positive patients (57.6 +/- 3.8 g/L, mean +/- SEM) than in the negative ones (35.7 +/- 6.4 g/L; probability value of the difference was less than 0.01). The erythrocyte eluates from DAT-positive patients contained a single immunoglobulin, of the same class as the M protein, and did not react with a panel of ABO-compatible erythrocytes. Addition of melphalan during incubation did not affect the results. The M protein of DAT-positive patients was of immunoglobulin G-3 subclass in 7 of 10 patients. A positive direct antiglobulin test frequently is seen in patients with multiple myeloma, the reaction is due to passive adsorption of the M protein onto the erythrocytes, is most frequently observed with immunoglobulin G3-MM, and usually does not produce hemolysis.
authors.affiliation: Department of Pathology, University Hospital, London, Ontario, Canada.
authors.forename: B I
authors.initials: BI
authors.lastname: Dalal
authors.forename: S Y
authors.initials: SY
authors.lastname: Collins
authors.forename: K
authors.initials: K
authors.lastname: Burnie
authors.forename: R M
authors.initials: RM
authors.lastname: Barr
mesh_terms: D000888:Antibodies, Anti-Idiotypic; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D009101:Multiple Myeloma / Q000175:diagnosis* / Q000276:immunology; D009194:Myeloma Proteins / Q000276:immunology; D011446:Prospective Studies; D012189:Retrospective Studies; D008258:Waldenstrom Macroglobulinemia / Q000175:diagnosis / Q000276:immunology
chemical_list: D000888:Antibodies, Anti-Idiotypic; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D009194:Myeloma Proteins