Heterophile antibody blocking agent to confirm false positive serum human chorionic gonadotropin assay.
BACKGROUND
Persistently false positive human chorionic gonadotropin (hCG) test results in the absence of an intrauterine pregnancy may lead to a diagnosis of ectopic pregnancy or gestational trophoblastic neoplasia and unnecessary testing and therapy.


METHODS
A 38-year-old woman on oral contraceptives and a 53-year-old perimenopausal woman presented with persistently elevated serum beta-hCG levels from 30 to 225 mIU/mL. Both women had a history of working with mice. Urine hCG testing was negative. Serum beta-hCG levels for both patients were negative after pretreatment of their serum with a heterophile antibody blocking agent.


CONCLUSIONS
These cases illustrate that serum heterophile antibodies can interfere with the hCG enzyme immunoassay and result in false positive values. The addition of heterophile blocking agent to the serum can exclude false positives, thereby preventing unnecessary evaluation and treatment.
Department of Obstetrics and Gynecology, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Navid
N
Esfandiari
Jeffrey M
JM
Goldberg
D000328:Adult; D000818:Animals; D019138:Antibodies, Blocking / Q000276:immunology*; D000910:Antibodies, Heterophile / Q000097:blood / Q000276:immunology*; D006063:Chorionic Gonadotropin / Q000097:blood*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007118:Immunoassay; D051379:Mice / Q000276:immunology*; D008875:Middle Aged
D019138:Antibodies, Blocking; D000910:Antibodies, Heterophile; D006063:Chorionic Gonadotropin