Very sensitive - sensitivity at 25mIU/ml of hcG in urine
Human chorionic gonadotrophin (hCG) is a glycoprotein hormone produced in the early stages of pregnancy by the syncytiotrophoblastic cells that will form the placenta. hCG is responsible for stimulating the corpus luteum to produce progesterone, maintaining the pregnancy. It is produced following implantation of the embryo and production rapidly increases (the levels approximately doubling every 48-72 hours) over the first 10-12 weeks of the pregnancy.
It is thought that the onset of morning sickness correlates to the increase in hCG over the first few weeks of gestation and it decreases as the levels of hCG start to decrease, around 12-14 weeks.
The hook effect occurs when blood, urine, or other samples contain too much of the substance that the specific pregnancy test is trying to detect. Instead of giving a positive result, the laboratory test becomes overwhelmed by the excess substance and provides a false-negative result.
Causes of excessively high hCG levels: