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Back to the Lab Articles
Friday, March 25,
2004
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OraQuick test is so easy to use
that it promises much better screening than currently used methods.
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The FDA approved OraQuick, a new HIV test on Thursday
that uses saliva and takes only 20-minute to perform. This is in contrast
to currently used ELISA techniques that may require confirmation with
Western Blot or other tests such as DNA PCR, RNA PCR, the (b)DNA assay,
or p24 antigen capture that usually take days.
It's not the only rapid HIV test available
however, other tests are much less reliable as regards their sensitivity
and specificity. In November 2002, the FDA approved a similar form of
OraQuick that uses blood for testing.
The new OraQuick test is so easy to use
that it promises better screening than currently used methods.
The person being tested using the oral form of OraQuick must place the device's absorbent pad above
the teeth and against the outer gum, then swab once around the upper
and lower outer gums.
The tester then puts the device into a vial containing a solution,
according to the test's maker. Reading the results is similar to reading
common pregnancy tests: A single reddish line on the OraQuick dipstick
means no HIV. Two reddish lines means the person may be infected and needs
a confirmatory test to be sure.
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The blood form of OraQuick requires
that a health worker simply pricks a person's finger, puts a spot of
blood into a vial containing a developing solution, and then dips in
the stick-like testing device.
The test, which is not approved for in-home or direct consumer use,
is more than 99 percent accurate, according to the FDA. Also, it has
not been approved to screen blood donors. The test detects antibodies to HIV, and
on the basis of data submitted by the manufacturer for test approval,
the sensitivity of OraQuick in the clinical studies performed was 99.6%
(95% confidence interval [CI]=98.5%--99.9%), and specificity was 100%
(95% CI=99.7%--100%), comparable to those of FDA-approved enzyme immunoassays
in widespread use.
The test will be a great help in identifying
pregnant HIV-infected women going into labor who were not tested during
pregnancy so that precautionary steps can be take to block their newborns
from being infected with HIV.
Health-care professionals must supervise OraQuick tests, and they
are responsible for delivering results to the person undergoing
testing. Positive results must be confirmed by another, more specific
test before being considered diagnostic.
In clinical studies, there were occasional false positive results
when OraQuick was read between 40 and 60 minutes. The revised
instructions indicate the test should be read no sooner than 20
minutes and no later than 40 minutes after the test device is inserted
into the developer vial. The change applies to both fingerstick whole
blood and venipuncture whole blood specimens.
An estimated one-fourth of about 900,000 HIV-infected people in the
United States do not know they are infected, according to the Centers
for Disease Control and Prevention. About 31 percent who get tested
and are positive never receive their results, emphasizing the
importance of rapid testing and rapid delivery of results.
OraQuick is not the first rapid HIV test
available. SUDS was one of the first rapid HIV tests licensed by FDA,
in 1992. It differs from the OraQuick test in that the SUDS test requires
serum or plasma as opposed to saliva or fingerstick whole blood for analysis, requires
more steps and takes longer to run, and requires refrigeration.
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