But the antibody test can be problematic for several reasons.

He'd just run the antibody test as well, and watched the tiny sample change color.

Indeed, most people will get negative results on an antibody test for three to six weeks after infection.

Rapid antibody tests are available that give results right away.

Once someone has had the disease, the antibody tests generally remain positive for years.

Despite all improvements, however, two problems will remain with antibody tests.

The antibody test shows whether you have been exposed to the virus.

A positive antibody test in a newborn did not show that the child was infected, although he or she could be.

Blood antibody tests, for example, range from 76% to 84% sensitivity.

As a result, health care providers avoid using them, and instead rely on the antibody test, which costs about $5.