Dear your question is not clear.

No test is foolproof. There will always be a few false negatives and a few false positives. Increasing the cost of testing will increase the cost of the products made from the blood, and make it unafordable for some people. Nothing is completely without risk, so the best we can do is minimize risk, we cannot eliminate it.

If the detection is performed in conditions mentioned below, the test mighy be negative, even though the donor is a carrier

1) the viral load is undetectable or undetectable antibodies

2) window period of the virus which differ significantly with type of virus and immune response of an individual