Interference of heterophilic and other antibodies in measurement of therapeutic drugs by immunoassays

Abstract

Heterophilic antibodies are human antibodies in a specimen which interact with assay antibodies to give false-positive or false-negative results. The heterophilic antibody may arise in a patient in response to exposure to certain animals or animal products, or to infection by bacterial or viral agents, or non-specifically. Among the anti-animal antibodies, the most common occurrence is of human anti-mouse antibody because of the wide use of murine monoclonal antibody products in therapy or imaging. Interferences from heterophilic antibody and anti-animal antibody in immunoassays are often grouped together as heterophilic antibody interference. Interference from auto-antibodies therapeutic anti-bodies, and rheumatoid factors (RF) is included in such interference. Such interferences are common with immunometric sandwich assays, but encountered only infrequently with competition (most common assay used in therapeutic drug monitoring/drugs of abuse testing) assays. Sample dilution, removal of interfering antibodies, or treatment of specimen with a heterophilic blocking agent prior to assay, has been recommended to remove heterophilic antibody interference. Thus, heterophilic antibodies are absent in the protein-free ultrafiltrate, and monitoring free drug concentration also eliminates this interference. © 2008 Humana Press Inc.