A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding .
Most pregnancy tests depend on the process of agglutination.
Some of the more sensitive tests use monoclonal antibodies rather than sensitized red blood cells. When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing . Serum HCG may also be increased in men with testicular tumors. It serves to maintain progesterone production by the corpus luteum in the early part of pregnancy.