AIDS Window Period
There is usually a period of several weeks in which newly infected people
have not yet produced enough HIV antibodies to be detected. The CDC said
there have been 35 AIDS cases since 1985 linked to blood from people in
this "window period."
Like the first generation of AIDS blood tests, current tests detect
antibodies to the AIDS viruses. Unfortunately, for a brief time after
infection, people make too few antibodies for these tests to detect. As a
result, their blood passes all the screening tests, even though it can
transmit HIV. The "window period" for HIV-1 lasts about 22 days
The FDA recommended in August 1995 that blood banks begin using the new p24
antigen test for HIV-1 when it became available. This test might cut 6 to
12 days from the window period=97at an added cost of perhaps $60 million each year.
Future tests may be based on the polymerase chain reaction (PCR), which can
detect HIV directly by detecting its genetic material.
PCR is sensitive enough to detect HIV in blood several days earlier than
the p24 antigen test. PCR was invented in the mid-1980s, and it gave
scientists a way to quickly and simply make millions of copies of genes for
their experiments. Molecular biologists could probe the gene defects
underlying cystic fibrosis, muscular dystrophy, and many other diseases.
Virologists could study the myriad variants of HIV-1 to determine how the
virus changes over time. Pharmacologists could measure the effects of
potential drugs on viruses. Archaeologists could track ancient human migrations .
Once refined by experimental scientists, PCR was eagerly adapted by
clinicians. Its sensitivity made it seem a natural for testing donated
blood for diseases.
So far, PCR has proved difficult to automate, a
necessity for processing the 14 million units of blood donated each year.
Also, PCR is expensive and, as viewers of the O.J. Simpson trial learned,
demands pristine handling conditions and meticulous technique. More
research is needed before blood banks can take advantage of PCRs power.
But protecting the blood supply from HIV-1 is not enough. Scientists
continue to discover other diseases that can be transmitted in blood. Also,
mistakes can occur. Blood can be mislabeled. Blood bank volunteers can
neglect to ask prospective donors all the required questions. Lab workers
can be sloppy in testing blood, or a test kit can be defective. Thousands
of errors and accidents are reported to FDA each year.
And even if cheap, reliable, error-proof screening tests were available for
every transmittable disease, transfusion would still not be 100% safe. No
medical procedure is . Transfusions cause some kind of problem in about 10%
of recipients. These problems range from fever and hives to iron overload
and congestive heart failure.
ABBOTT PARK, Ill., April 24, 1996
-- Abbott Laboratories (NYSE: ABT) today
announced the United States Food and Drug Administration (FDA) has cleared
for marketing the companys new test for the virus that causes AIDS. The
test is intended for the detection of the HIV-1 p24 antigen of the human
immunodeficiency virus (HIV).
The test, to be sold under the name Abbott HIVAG-1 Monoclonal, is an enzyme
immunoassay (EIA), and is the second FDA-licensed HIV antigen detection kit
intended for use in blood banks and plasma centers nationwide according to
new FDA blood screening recommendations. Abbott HIVAG-1 Monoclonal is also
cleared for prognostic use in HIV-infected patients.
"The test reduces the window period between HIV infection and
detection the first 25 to 45 days, when the virus can elude efforts to screen it out," said
Ronald Gilcher, M.D., president and CEO, Sylvan N. Goldman Center, Oklahoma Blood
Institute, where the test has been researched since 1991. "The new test also cuts
testing time to four hours from 24 from Abbotts earlier version antigen test."
HIV antibody testing has been used by all U.S. blood institutions to screen
donated blood and plasma for HIV infection. This new test will allow U.S.
blood screening centers to have an alternate source for the p24 antigen
test. (HIV antibody tests will continue to be used in parallel to identify HIV positive
blood.) While antibody testing can measure the bodys immune response to the presence
of a virus, antigen testing detects the virus itself. Patients infected with HIV may have
positive antigen results very early in the infectionbefore a substantial antibody
response has formed. As a result, people recently infected with HIV may be identified by
the antigen test while the antibody test remains negative or indeterminate until a later
I hope this information is of some assistance.
David A. Reznik, D.D.S.
Some notes and a link
The "window period" is the time it takes for a person who has been infected with HIV to react to the virus by creating
"Antibodies generally appear within three months after infection with HIV, but may take up to six months in some
The three month window period is normal for most of the population. Many people will have detectable antibodies in
three or four weeks. Very, very rarely, a person could take six months to produce antibodies.
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One Reader Asked :
On 8 th may 2007 ,I had a sex with a prostitute and condom breaks a little and it
contacts for 3-5 seconds .
I feel many symtoms after 3 weeks ( fatigue and tiredness, no fever )
after 6 weeks no fatigue but headache and sore throat .( no fever till
now) after 4 weeks i got my rapid test negative after 6 weeks i find that girl and request her to test
and got her test negative . After 52-53 days I went to labortory and got my western Blot test ( He takes three days to deliver the result )
the result of Western Blot test is as follows
GP 41 negative
GP 120 negative
GP 160 negative
HIV-2 Specific antibody -- negative
Serium Control band Reactive
After this , Doctor told me you need not to worry bcoz this test is
effective within 2 weeks after exposure. Is it true
I am still tense , Please answer me is this test after 53 ( ~8 weeks)
is reliable to me ) ????? Please answer , I m very tense , One of my relative is asking me to donate blood for his father , should i donate . please tell me ???
The chance of HIV transmission by way of single sexual contact is about 25%, going by chance factor; ie. One in 4 will get the infection. Obviously chance increase with multiple exposures.
Rupture of protective condom can prone one to high risk.
Local factors in the genital tract are also important. Other local infections, ulcers, mucosal trauma etc contribute of higher chance.
Prophylaxis with medicines can prevent transmission if taken as early as possible after exposure, preferably within a day of contact. Medicines are not of known benefit after 1 month.
PCR test can confirm the disease early after contact (95% detection after 6 weeks). ELISA and Western blot can be falsely negative upto 3-4 months. Similarly, a negative test in the sex worker may not mean 100% negative result, if the lady is in window period.
If you are negative even after 6 months, means you should have not acquired the infection. In such a fortunate situation, it is wise to avoid sexual mis-adventures in future!
Your WB test is negative at this point (nearly 50 days; less than 2 months). It is most likely that you are un-infected. However, as a possibility of still 5-10% chance, it is worthwhile to not donate blood for 6 months post exposure. A negative WB or ELISA at 3 months will however make you 99% negative and at 6 month, 100% negative. If there is an emergency to donate, a negative DNA PCR test at this point can be done which can suggest that you are 99% negative.
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