Interference in T3 Radio immunoassay due to heterophil antibodies

Autoantibodies and heterophile antibodies may be interfere with immunoassay methods and yield false results, leading to incorrect diagnosis and consequently inappropriate diagnostic and therapeutic interventions, which eventually may not be only costly, but also endanger the patient’s health. Interference of autoantibodienature are usually analyte specific (i.e Anti-T3 interfere only in T3 assay) and those due to heterophile antibodies are usually method specific (such as IRMA or two-site methods). This is a case report of a patient presenting with nonspecific symptoms suspected of hyperthyroidism the TFT, and T3 evaluations were more than twice were normal range exclusively by RIA method. After ruling out interferences due to binding proteins disorders and autoantibodies by in house methods, use of blocking and removal technique show that this false result in T3 assay was caused by a heterophile antibody from Ig G class. In our review of literature this is the first case report of interference in exclusively T3 assay by RIA method due to the heterophile antibody.