Limitations of the Human Chorionic Gonadotropin (hCG) Assay in the Diagnosis of Gestational Trophoblastic Disease

A 31-year-old lady presented with abnormal vaginal bleeding during her first trimester of pregnancy. Based on the ultrasound findings and decreasing hCG trend (from 1040 mIU/mL to 759 mIU/mL), a diagnosis missed miscarriage was made. week later, patient heavy bleeding. Ultrasound showed classic snowstorm appearance suggestive complete hydatidiform mole. The serum level however, 357 mIU/mL. In case hydatiform mole inappropriately low hCG, analytical interference suspected. Post- dilution 5,775,000 confirmed presence hook effect in two-site immunoassay. Discordance between clinical should be actively investigated by laboratory prevent delay treatment. This also highlights need for clinicians aware assay used their hospital’s so that they may recognise false negative results.