The presence of heterophile antibodies may be associated with a false positive immunoassay.
Heterophile antigens are antigens shared by 2 or more species of organisms that are phylogenetically unrelated.
Heterophile antibodies:
(1) are low-affinity IgM antibodies, usually present in low titer and targeting carbohydrate antigens
(2) may be increased in certain conditions
Some authors refer to rheumatoid factor as a heterophile antibody, but rheumatoid factor targets the Fc portion of immunoglobulins rather than carbohydrate antigens.
Heterophile antibodies may be increased in:
(1) infectious mononucleosis
(2) malignant lymphoma
(3) leukemia
(4) idiopathic
(5) other viral infections (viral hepatitis, HIV, etc)
Some immunoassays affected:
(1) serum troponin
(2) plasma D-dimer
(3) rubella IgM assay
(4) serum vitamin D
Recognition:
(1) The presence of a positive test result but no evidence of an underlying cause.
(2) The analyte gives normal or much lower results if the sample is pretreated to block heterophile antibodies or if an alternative method is used.
Some ways to remove the interference:
(1) dilution of sample
(2) polyethylene glycol precipitation
(3) heterophilic antibody blocking reagent
