conjugate binds to hcg antigens forming antibody antigen complex in the fluid sample which is captured by antibody in the test line and causing the test area to become visible when the hcg concentration in the sample is more than 2 000 miu ml or 10 000 miu ml antibody gold conjugate binds to the hcg antigen in the sample and can not be further bind to the hcg antigen in the test area thus produce no respective test line when the hcg level in sample is below the respective detection limit the unbound antibody gold conjugate will be bound to the hcg antigen at the test line thus produce a visible test line if the hcg concentration in the sample is less than 25 miu ml the test area of 25 miu ml 100 miu ml and 500 miu ml are invisible while the 200 miu ml and 10 000 miu ml test areas are visible control areas are always visible if the correct procedure is followed if the hcg concentration in the sample is higher than the respective detection limits of 25 miu ml 500 miu ml and 1000 miu ml the respective test areas of the test strips becomes visible while the 200 miu ml and10 000 miu ml test areas are.