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Anonymous
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NAT testing
      #83745 - 01/30/04 04:27 PM

Does anyone know anything about Nucleic Acid Testing (NAT) I was told that blood banks use it to seek the virus in donated Blood. How effective is it? I have had numberous negitive Elisa test from home Access over the past six months( with no risky exposures in many many months) If I go and donate blood will my results be clean? Given my past tests from Home Access?

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rjasin123
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Reged: 01/27/04
Posts: 410
Re: NAT testing new
      #83759 - 01/30/04 05:33 PM

What you are referring to here is NAT testing (Nucleic Acid Amplification Testing), which includes tests such as the PCR. NAT tests for the virus itself, rather than antibodies to the virus. NAT tests are now beginning to be used to screen the blood supply for HIV and hepatitis C. NAT tests are still investigational (experimental) and are not yet FDA approved for this purpose!

The major drawback of the standard antibody tests is the so-called "antibody window period", the time it takes from infection to when the body produces antibodies. The purpose of NAT testing is to shorten the period of time from infection, to when we are able to detect an infection in the blood, thus reducing the risk to the blood supply. NAT tests will be done IN ADDITION TO currently used screening tests in the blood supply. They will not replace presently used tests.

NAT testing has been proposed for screening the blood supply for HIV, as well as screening for the hepatitis C virus (HCV). Thus far, NAT has not been shown to be beneficial for screening for the hepatitis B virus. NAT testing is expected to reduce the average window period for HIV by several days. As far as hepatitis C is concerned, NAT testing may reduce the average window period by several weeks. Because NAT testing will only reduce the average HIV window period by only a few days, it is not expected to make a significant difference in reducing the already low risk of HIV to the blood supply (however public fear of HIV is why NAT testing for HIV is being added to blood screening, despite it's limited additional benefit in screening the blood supply). In comparison, NAT testing will shorten the average hepatitis C window period by potentially weeks, making NAT testing for HCV a higher priority in screening the blood supply.

Because NAT testing is very complicated and difficult to do, they will not be testing individual units of blood with this test. Rather, they will be pooling together multiple samples of blood, and then doing an NAT test on the pooled samples. If the pooled sample is found to be positive, further tests will need to be done to try to determine which individual sample (in that pooled sample) is the potentially infected sample.

Blood will not be released unless currently used tests all come back negative for HIV, hepatitis B, hepatitis C (HCV), HTLV-I/II and syphilis. However, because NAT testing for HIV and HCV is more difficult to do (and therefore more time consuming), it is possible that samples of blood that tested HIV and HCV antibody negative on currently used tests, will be released before NAT testing is completed. It is therefore a possibility that blood which tested antibody negative for HIV and HCV will be released, and later on NAT testing may indicate a possible infection, after the blood is released (and possibly transfused).

It must strongly emphasize that the risk of getting HIV, hepatitis C and other bloodborne diseases from receiving a blood transfusion is already very low. These investigational (and thus far unapproved) NAT tests are being evaluated to see how well these tests can be used to further lower the already low risk of HIV and HCV to the blood supply. Until these studies are completed, the accuracy and added benefit of these tests are not yet known. But they are expected to potentially lower the risk of infection when receiving a blood transfusion, especially as it relates to the risk of hepatitis C.

I must also emphasize that you should NOT donate blood just to take these NAT tests. In fact, people trying to donate blood just to take these tests will be prevented from donation. You should NEVER donate blood just to be tested for HIV and other bloodborne diseases.

For further information about NAT testing in the blood supply, please read the following "Question and Answers" from the American Association of Blood Banks.

Association Bulletin #99-3 (8 February, 1999)

Questions and Answers about Nucleic Acid Amplification Testing (NAT)

Q1. If blood components and products are already safe, why is NAT being implemented?

A1. The implementation of NAT will significantly shorten the serologically negative window period the time between when a person is infected with a virus and when current screening tests can detect it for the detection of hepatitis C virus (HCV), and provide a smaller decrease in the window period for human immunodeficiency virus (HIV). We expect there to be very few units that fit into this latter category.

Q2. How is NAT different than the current tests used to screen blood?

A2. NAT employs a new form of testing technology that directly detects the genetic material of viruses like HCV and HIV. Because NAT detects the genetic material of a virus instead of having to wait for the human body’s response to a virus the formation of antibodies against it, as is the case with most current tests it offers the potential advantage over the current tests of reducing the window period, thus further improving blood safety.

NAT is still a research initiative, however, and the degree to which safety may be affected is not yet known. Several issues must be resolved through research before NAT can be implemented for all volunteer blood donations.

Q3. If NAT is still in a research and development stage, how can it be used to test blood?

A3. The use of NAT has not been approved by the Food and Drug Administration (FDA) for donor screening in the United States. Because of the promise that this technology holds for even further improving the safety of the blood supply, many blood collection organizations are pursuing the implementation of NAT under the FDA’s Investigational New Drug (IND) application process. This process will allow blood collectors to conduct NAT under certain guidelines so that they and the FDA can track the progress of this research initiative.

Q4. Will this technology be available for all voluntarily donated blood?

A4. The vast majority of FDA-licensed blood collecting facilities are implementing NAT. Other blood centers and hospitals that are interested in testing are encouraged to contact the American Red Cross or America’s Blood Centers for further information on participating in their programs.

Q5. Will NAT affect the availability of blood components/products?

A5. No. The intent is that the implementation of NAT not affect the availability of blood components or plasma derivative products.

Q6. Why are blood collection organizations implementing NAT before they can control component release on the basis of its results?

A6. Because demand for blood is high, units are often used shortly after they are collected. Not releasing components until the results from NAT are available might hold back much-needed cellular components from patients in need. Blood is as safe as it has ever been, so recipients of blood transfusion are at a very low risk of transfusion-associated infections. Some transfusion-associated infections do occur, however rarely.

Early on in this process, the addition of NAT will prevent some of these infections, and it will allow others who have received a transfusion of a unit that was in the HIV or HCV window period of the currently licensed screening tests to learn earlier of the infection and to seek counseling and treatment, as well as to prevent such recipients from infecting others.

In addition, the early stages of NAT will provide experience that will allow blood collection organizations to further develop this sample and receipt management process and allow the organization to reach a point where the turnaround time of NAT approaches that of current screening tests.

Some of these processes cannot readily be optimized without initiating testing. Blood collectors feel that the benefits of initiating testing earlier under IND outweigh the advantage of delaying implementation until NAT can be performed with an efficiency that allows for the release of all components on the basis of NAT test results.

Q7. What is the exact process for addressing a situation where a NAT-reactive unit is transfused before the NAT test result could be obtained?

A7. In the case of HIV, which will be extremely rare, the hospital where the patient received the transfusion should use its existing mechanisms for post-exposure prophylaxis and counseling. In the case of HCV, where there is no consensus on the utility of post-exposure treatment, hospitals should employ their standard counseling procedures for HCV (more detailed information on HCV counseling is available in the October 16, 1998, publication Morbidity and Mortality Weekly Report, Recommendations for Prevention and Control of Hepatitis C Virus (HCV) Infection and HCV-Related Chronic Disease issued by the Centers for Disease Control and Prevention), and consider consultation with experts on the evaluation and treatment of HCV infection.

Q8. How many HCV- and HIV-infected units do you expect to detect only through NAT?

A8. The risk of HCV and HIV in volunteer donors is very low, the current licensed screening tests are very sensitive, and NAT will serve to shorten the window period and further decrease the possibility of transmission of HIV or HCV via transfusion. The currently estimated rates of NAT-reactive donations among those volunteer donors that test negative for currently performed screening tests for anti-HIV-1/HIV-2 and anti-HCV the so-called window period donations is 1 per one million donations for HIV, and 1 per 20,000 to 100,000 for HCV.

Q9. Will NAT affect the price of blood products?

A9. When implemented, NAT will add incrementally to the cost of processing a unit at a blood collection center.

Q10. Why can't the NAT test results be obtained before the components are sent to hospitals?

A10. Turnaround time for NAT test results on a single unit may be longer than for any of the standard blood donor screening tests currently in place. This additional turnaround time is the result of several factors, including (1) the length of time required for pooling samples from multiple donors for testing, (2) the performance of the test itself, and (3) the subsequent NAT r

source: thebody.com expert advice.....

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Anonymous
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Re: NAT testing new
      #83774 - 01/30/04 06:04 PM

thank you for your prompt reply! Do think given my history of several negitive Home Access tests out to 33 weeks post exposure and no recent risk exposures that I can safely give to a blood bank ( not my safety)

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rjasin123
Guardian

Reged: 01/27/04
Posts: 410
Re: NAT testing new
      #83869 - 01/30/04 08:10 PM

With out a shadow of a doubt, you can give!

Cheers

Jazz

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Anonymous
Unregistered

Re: NAT testing new
      #84701 - 02/02/04 12:08 PM

If you tested out to the 6 month mark then you do not have HIV. If you want to donate for the sake of helping someone and not just to get an HIV test, then go ahead. They will screen you and ask you many questions on your sexual history. High risk activity will ban you from donating anyways.

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Anonymous
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Re: NAT testing Jazz please help!!!!!!!! new
      #85905 - 02/05/04 03:49 PM

Jazz you are most kind in your replies thank you. I was taken back alittle when after I donated blood one nurse was explaining to me that the blood is very quickly tested and that if I did not hear anything back from the blood bank within two weeks it was safe to assume that the blood checked out alright. She was interupted by another nurse who said that was true but in some cases it could take up to but no longer than two months to inform a donor of a problem. That made me alittle unsettled. Could NAT testing account for that two month period. It has been 3 weeks since my donation and no word yet! Can you offer an insight?

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rjasin123
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Reged: 01/27/04
Posts: 410
Re: NAT testing Jazz please help!!!!!!!! new
      #85927 - 02/05/04 08:17 PM

No, NAT testing is not the cause of the delay. It is simply how they process your sample .

This is normal and no reason for concern.

Futhermore, you have tested reliably negative. No worries here.

Jazz

Jazz

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