June 16 (Bloomberg) -- Inaccurate results from Orasure Technologies Inc.'s oral AIDS test have spurred New York City, the user of 60,000 detection kits a year ago, to stop using the screens to test saliva in clinics. The company fell 13 percent in New York trading.

The rate of false positives from the OraQuick Advance Rapid HIV 1/2 rose as high as 1.1 percent over the past eight months, or more than five times the level claimed in the kit's labeling, city health officials said. While the test meets U.S. standards and remains on the market, New York's sexually transmitted disease clinics stopped using it to screen saliva on May 27, said Susan Blank, director of the city's Bureau of STD control.

The $12 test is the only one cleared in the U.S. to test saliva for signs of HIV. It generated $32.7 million in 2007 sales, or about 40 percent of company revenue, Orasure said in February. The kit has performed better elsewhere, according to company spokesman Ron Ticho, who said Orasure is cooperating with U.S. regulators reviewing the New York results.

Nothing links the false positives to how the clinics have used the test, Blank said in a June 13 e-mail. ``So far, false positives have not been linked to handling, storage conditions, lot numbers, clinic sites and test operators,'' she wrote.

Orasure, based in Bethlehem, Pennsylvania, fell 68 cents, or 13 percent, to $4.51 at 4 p.m. New York time in Nasdaq Stock Market composite trading, and has lost 37 percent in the past 12 months before today

Widely Used

OraQuick, which can also be used to test blood, is widely used because of its speed, convenience, and acceptability to patients who prefer giving saliva to blood. Ireland-based Trinity Biotech Plc and Chembio Diagnostics Inc. of Medford, New York, make rapid screens to detect signs of the AIDS virus in blood that cost about $4 less per test, according to the Centers for Disease Control and Prevention Web site.

More than 1 million people in the U.S. have HIV, the virus that causes AIDS, according to the Centers for Disease Control and Prevention. President George W. Bush has been pushing widespread testing to help identify about one-quarter of them who may be spreading the disease without knowing it.

In more than 250,000 tests over the past 17 months at 400 sites across the country, OraQuick has performed well, with a 0.2 percent false positive rate, Orasure's Ticho said.

`Slight Aberration'

``What's happening in New York City appears to be a slight aberration,'' Ticho said today in a telephone interview. ``Performance results may fall slightly outside the expected range for a short period of time. That's expected.''

Other city health department clinics continue to use the oral test, Ticho said. Following standard company procedure for investigating product performance, Orasure is working with the CDC and New York to understand the issue, he said.

``Oral fluid testing continues to be a very important component of HIV prevention in New York City and around the nation,'' said Douglas Michels, Orasure's president and chief executive officer, in a statement.

The CDC is investigating whether health officials in other cities are experiencing similar problems with the oral tests, said Bernard Branson, associate director of laboratory diagnostics for the agency's division of HIV/AIDS prevention.

False positive results might needlessly concern patients, he said. Blank has filed a report with the CDC, he said, and the agency is considering publishing a notice in its Morbidity and Mortality Weekly Report, a publication used to alert health officials about unexpected events.

Elevated Rates Previously

``When oral testing showed low numbers of false positives, that reassured everyone,'' Branson said. ``When that changes, people need to find out what the problem is and get to the bottom of it.''

New York, along with health departments in San Francisco, Minnesota, and Utah, found similar elevated rates of false positives with the test in 2004 and 2005. New York decided at that time to confirm any positive OraQuick oral test with the same test, using a blood sample, Blank said.

When blood tests came up negative, health workers would tell the patient that they should consider their testing inconclusive until it could be confirmed with a third test for viral genetic material, called PCR, she said.

New York Health officials began to notice the recurrence of earlier problems in October, and it persisted through April, Blank said. Although results from the test returned to normal in May, the department's 10 STD clinics stopped using oral testing.

Some San Francisco testing sites haven't gone back to oral testing since 2005, when problems with false positives first arose, said Grant Colfax, director of HIV prevention for the city's public health department. Clinics that continue to use the test haven't seen recent increases in false positive rates that would suggest it shouldn't be used, he said.

``We look forward to reviewing the New York data to see if there's sufficient concern to consider changing that policy,'' Colfax said in a telephone interview today.

To contact the reporter on this story: John Lauerman in Boston at jlauerman@bloomberg.net.

Last Updated: June 16, 2008 18:05 EDT