title: Heterophilic antibody interference affecting multiple hormone assays: Is it due to rheumatoid factor?
abstract: Assay interference with heterophilic antibodies has been well described in literature. Rheumatoid factor is known to cause similar interference leading to falsely elevated hormone levels when measured by immunometric methods like enzyme-linked immunosorbent assay (ELISA) or multiplex immunoasays (MIA). We report a case of a 60-year-old male patient with a history of rheumatoid arthritis referred to our endocrine clinic for investigation of hypogonadism and was found to have high serum levels of LH, FSH, SHBG, Prolactin, HCG and TSH. We suspected assay interference and further tests were performed. We used Heteroblock tubes and PEG precipitation to eliminate the interference and the hormone levels post treatment were in the normal range. We believe the interference was caused by high serum levels of rheumatoid factor. Although he was treated with thyroxine for 3 years, we believe he may have been treated inappropriately as his Free T4 level was always normal despite high TSH due to assay interference. Our case illustrates the phenomenon of heterophilic antibody interference likely due to high levels of rheumatoid factor. It is essential for clinicians and endocrinologists in particular to be aware of this possibility when making treatment decisions in these groups of patients.
authors.affiliation: a Department of Diabetes & Endocrinology , Hull Royal Infirmary , Hull ;
authors.forename: Shiva
authors.initials: S
authors.lastname: Mongolu
authors.affiliation: b Department of Clinical Biochemistry , University Hospital Southampton , Southampton ;
authors.forename: Annie E
authors.initials: AE
authors.lastname: Armston
authors.affiliation: c Department of Chemical Pathology , Guys and St. Thomas Hospital , London , UK ;
authors.forename: Erin
authors.initials: E
authors.lastname: Mozley
authors.affiliation: d Department of Endocrinology , Putrajaya Hosital , Malaysia.
authors.forename: Azraai
authors.initials: A
authors.lastname: Nasruddin
mesh_terms: D000910:Antibodies, Heterophile / Q000097:blood*; D016477:Artifacts; D005188:False Negative Reactions; D006801:Humans; D007006:Hypogonadism / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D012217:Rheumatoid Factor / Q000097:blood*
chemical_list: D000910:Antibodies, Heterophile; D012217:Rheumatoid Factor
keywords: Heterophilic antibody interference; PEG precipitation; immunoassay interference; immunoassays; rheumatoid factor