First 171 words of the document:
HOW PREGNANCY TEST STRIPS WORK
Pregnancy test strips work by detecting a special hormone produced by the fertilised egg
called human chorionic gonadotrophin (hCG). This hormone can be found in
urine and therefore, urine test strips uses a method called lateral flow
immunoassay (a biochemical test involving antibodies and capillary action) to detect it.
The strip itself is made of a capillary membrane that is able to draw urine, through capillary
action, along its length.
If the pregnancy test is negative, there will only be one pink line as shown below. As there is
no hCG to bind to, the antihCG antibodies in the reaction zone simply dissolves in the urine
arrives at the test zone. The polyclonal antibodies have no hCG to bind to either, so the
antihCG monoclonal antibodies aren't trapped in the test zone and bind to the
antimonoclonal antibodies in the control zone and only triggering the colour reaction in that