Officials say they're confident in accuracy of SARS test

ATLANTA -- Federal health officials said Thursday they are confident about the accuracy of the main antibody test being used to screen people for SARS.

The Centers for Disease Control and Prevention administered the test to more than 500 people -- some suspected of having SARS, some known not to be infected -- and said no one tested positive for the disease who did not have it.

"It's a good test," said Dr. Larry Anderson, a CDC virus expert. "I think it's going to help a lot on understanding SARS."

Anderson said it is possible that the tests could show false-negatives -- that is, people infected with the virus could test negative for the virus -- but he said such cases would probably be infrequent.

The test identifies an antibody to the coronavirus believed to cause SARS, or severe acute respiratory syndrome.

Scientists still need to develop a test that can detect infection earlier, Anderson said. Sometimes the antibody test does not detect the virus until four to six weeks after a person shows symptoms.

A test that can detect the virus soon after infection would enable health authorities to avoid having to quarantine large numbers of people suspected of having the disease.

The CDC tested nearly half of the 66 probable SARS cases in the United States. Only seven people -- about 22 percent -- had the antibody, not surprising to health officials, because many probable SARS patients may actually have a different respiratory illness.

Of the probable cases, 59 percent were adults, 20 percent senior citizens and 12 percent children. The cases were nearly evenly divided between whites and Asians, and 65 percent had been hospitalized, the CDC said.