Serum heterophile antibodies interfere with prostate specific antigen test and result in over treatment in a patient with prostate cancer.

Abstract

We evaluated how naturally occurring heterophile antibodies in patient serum interfered with prostate specific antigen (PSA) immunoassay, resulting in over treatment for prostate cancer. Serum samples were treated with heterophilic blocking reagent (Scantibodies Laboratory, Inc., Santee, California). Treated and untreated samples were tested by the Medics (Tosoh, Foster City, California ) Tandem-R (Beckman-Coulter Inc., Chaska, Minnesota) and Elecsys (Roche Molecular Biochemical, Indianapolis, Indiana) PSA assays. Heterophile antibodies were measured directly in treated and untreated samples by the human anti-mouse antibody immunoradiometric assay and heterophilic antibody identification enzyme immunoassay (Scantibodies Laboratories, Inc.). Human anti-mouse Ig heterophile antibodies in patient serum caused false-positive PSA test findings after radical prostatectomy, resulting in over treatment for presumed disease recurrence. If PSA is detectable after radical prostatectomy and the likelihood of incomplete resection or systemic disease is low, the presence of heterophile antibodies should be considered.