How are monoclonal antibodies used in pregnancy tests?

* A hormone called HCG is found in the urine of pregnant women

* Pregnancy testing sticks detect this hormone. This is how they work:

* The bit of the stick you wee on has some antibodies to the HCG hormone with

blue beads attached.

* The test strip (which turns blue if you are pregnant) has some more antibodies

to the hormone stuck on to it, so they can’t move.

* The HCG hormone binds to the antibodies on the bit of the stick where you wee

and the antibodies on the test strip.

If you’re pregnant and you wee on the stick:

* The HCG hormone binds to the antibodies attached to the blue beads.

* The urine moves up the stick carrying the HCG hormone and the blue beads

with it.

* The blue beads and HCG hormone bind to the antibodies on the test strip –

so the antibodies get stuck on the test strip turning it blue – showing you

are pregnant.

If you’re not pregnant and you wee on the stick:

* The urine still moves up the stick carrying the blue beads. * But because there is no HCG hormone to bind to the antibodies on the test strip it doesn’t go blue.