“High-dose hook effect” - negative urine β-HCG in molar pregnancy

Abstract

The hydatidiform mole, commonly known as molar pregnancy is characterized by the abnormal proliferation of trophoblasts. A hallmark of diagnosing hydatidiform mole is a positive β- hCG assay pregnancy test. Currently used β- hCG assays are sandwich chromatographic immunoassays and may sometimes produce false-negative results in the presence of excessively high antigen concentrations, a phenomenon known as the “high-dose hook effect”. We report an atypical case of molar pregnancy in a 24-year-old primi gravida female who presented to us in emergency department with a huge abdominopelvic mass, respiratory distress and bilateral pedal edema with a negative urine pregnancy test. Ultrasongraphy suggested it to be hydatiform mole and on further evaluation serum β- hCG was found to be raised. Repeat urine β- hCGassay showed positive result on 1:10 dilution. After resuscitation, patient was treated with suction and evacuation which demonstrated grape like vesicles with no fetal parts. Histopathology report revealed it to be complete hydatiform mole.