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New Guidelines for Oral HIV Testing Due to False Positive Tests
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"Changes planned in use of oral HIV test
Blood to be checked quickly to confirm any positive results"
San Francisco Chronicle
Sabin Russell, Chronicle Medical Writer
Saturday, December 10, 2005
Federal health authorities plan to issue new guidelines on the use of an oral HIV test after testing centers in New York and San Francisco began reporting an unusual number of false positives in recent months.
Approved by the Food and Drug Administration in March 2004, the OraQuick Advance test shows results within 20 minutes using fluids swabbed from the mouth, a breakthrough in easy-to-use HIV testing that is being considered for over-the-counter sales to consumers.
However, public health clinics in San Francisco have now recorded at least 49 instances since May in which clients tested positive on the oral HIV test, but subsequent confirmation tests showed they were negative.
In New York City, clinics encountered a sudden increase in false positives with the oral test -- recording 10 in October and 30 in November alone, according to a San Francisco health official.
Dr. Bernard Branson, associate director for Laboratory Diagnostics at the Centers for Disease Control and Prevention in Atlanta, said the federal agency will issue an advisory that clinics offer patients who test positive on the oral test an immediate rapid retest using a droplet of blood.
"What we intend to suggest is that if someone is tested with oral fluid and is positive, that person -- if it is possible at the clinic -- should get a finger stick test,'' he said.
Even if the blood test is negative, the person will still need to have the results confirmed by more sophisticated Western Blot laboratory tests -- a process that can take a week -- but he or she can go home with much greater assurance that the initial oral test was probably erroneous.
Clinics that are able to draw blood using the finger stick method can use the same OraQuick product, which is licensed to process oral fluid, blood droplets, or blood drawn into a test tube. The finger stick test also produces results in 20 minutes, and no comparable reliability issues for it have been raised.
Branson said the advisory is likely to be issued in next week's edition of the Morbidity and Mortality Weekly Report, the Centers for Disease Control and Prevention's epidemiology bulletin.
Douglas Michels, chief executive of Orasure Technologies, the Bethlehem, Pa., maker of the test, said that despite the cluster of false positives in San Francisco, the overall performance of the test has been within the guidelines set for it by the FDA.
He said a team from the company traveled to San Francisco after reports of the false positives arose a month ago. "It is quite common that if there are unusual results, we will investigate,'' he said.
In 2005, he said, the company has received a total of 20 complaints from a customer base of more than 1,300 hospitals and clinics. Out of 28,436 tests, there have been 107 reports of false positives -- an accuracy rate of 99.6 percent.
Branson said that the false positive rate in large-scale monitoring of the test is also showing a 99.6 percent accuracy rate -- meaning 4 false positives can be expected out of every 1,000 tests. That figure is comparable to the best blood tests available.
However, he said he is "not comfortable" with clusters of false positives reported in San Francisco and New York. Although he would not specify the number of false positives in New York, he said, "They had a fine August and September, but an increase in October and a considerable increase in November. They had a spike, but their overall numbers (for the full year) are good.''
Orasure chief executive Michels declined to comment on the New York numbers. On Thursday, he had said New York had not had a problem similar to San Francisco's.
Teri Dowling, manager of HIV counseling and testing for the San Francisco Department of Public Health, said New York health officials have told her they were having three to five false positives a month until October, when the number rose to 10; then the count jumped to 30 in November.
New York officials could not be reached for comment.
Dowling said she is pleased that the CDC appears ready to recommend a follow-up rapid test with a blood droplet. "We think it is a great solution,'' she said. "It reduces the time it takes for a person to think they are likely positive, if they are probably negative,'' she said.
Orasure's Michels said he has not discussed a change in the recommendations for use of the test with the Centers for Disease Control and Prevention. "I can't propose anything other than for what the product is approved,'' he said.
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