HCG (human chorionic gonadotrophin) is a hormone found in the body when pregnant or if the body is fighting cancer.
Pregnancy tests are based on detecting levels of HCG in the urine. Most pregnancy tests are based on detecting low levels of HCG however Boots own brand of pregnancy tests (and many others) are based on detecting 50 units or more of HCG in the body.
If there are 49 units or more of HCG in the body and not pregnant there is a possibility that the body is fighting cancer.
Therefore the Boots own test which only gives a positive reading for 50 units or more of HCG is the only test suitable for early detection of cancer.
There are other tests that can be done to find out exactly how much HCG there is in the body. These are more complex and cost approx. £50, sending urine samples to America but a good way to monitor your fight against cancer.