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DNA PCR Testing Question?
Doc,
I have been searching online for more info regarding DNA PCR Testing of HIV. Across the boards I have seen a negative consenus on using this test for low risk exposures.
What would be the right time window to take a DNA PCR test? The test looks for HIV virus DNA, so wouldn't be more accurate earlier than anti-body. Isn't the DNA present regardless of antibodies?
My concerns are over a 1 time unprotected vaginal sex encounter with a female friend of mine (she said she does not have HIV, she had sex 1 other time only, unprotected though, between her last HIV test (neg)). At 40 days (5 weeks,5 days) I could not deal with the stress anymore and took a anti-body test and DNA PCR test (labcorp test from www.areuatrisk.com) and both were negatvie. I have read all of the posts with time to test positive, etc. If seroconversion hadn't happened at 40 days yet, would a PCR negative results still be valid. The reason why I am posting is at 70 days post exposure I am having some pressure (not necessarily pain) on the left side of my groin (I can't tell if my lymph nodes are swollen) and have had a headache. I really want to move on from this, as I am about to buy my first home and finally start my adult life. After the negative results I was fine, but once I felt some pressure in my groin, I started to be concerned again.
If seroconversion hadn't happend yet at the time of the anti-body test, how reliable would the DNA PCR be at 40 days. Is the false positive rate and cost of the test the real downside to this testing method, but otherwise it is a very good test? there is not a lot of information online about this testing method - besides people recommending not to take it for the false positive rate.
Also, would you recommend a retest?
Thanks for all of your help!
I have been searching online for more info regarding DNA PCR Testing of HIV. Across the boards I have seen a negative consenus on using this test for low risk exposures.
What would be the right time window to take a DNA PCR test? The test looks for HIV virus DNA, so wouldn't be more accurate earlier than anti-body. Isn't the DNA present regardless of antibodies?
My concerns are over a 1 time unprotected vaginal sex encounter with a female friend of mine (she said she does not have HIV, she had sex 1 other time only, unprotected though, between her last HIV test (neg)). At 40 days (5 weeks,5 days) I could not deal with the stress anymore and took a anti-body test and DNA PCR test (labcorp test from www.areuatrisk.com) and both were negatvie. I have read all of the posts with time to test positive, etc. If seroconversion hadn't happened at 40 days yet, would a PCR negative results still be valid. The reason why I am posting is at 70 days post exposure I am having some pressure (not necessarily pain) on the left side of my groin (I can't tell if my lymph nodes are swollen) and have had a headache. I really want to move on from this, as I am about to buy my first home and finally start my adult life. After the negative results I was fine, but once I felt some pressure in my groin, I started to be concerned again.
If seroconversion hadn't happend yet at the time of the anti-body test, how reliable would the DNA PCR be at 40 days. Is the false positive rate and cost of the test the real downside to this testing method, but otherwise it is a very good test? there is not a lot of information online about this testing method - besides people recommending not to take it for the false positive rate.
Also, would you recommend a retest?
Thanks for all of your help!
MEDICAL PROFESSIONAL
You are well beyond the time frame for use of the PCR test to detect HIV infection and should not have had that test. The idea is to diagnose infections before antibody develops, typically a few days to 2-3 weeks after exposure--and even then, only in much higher risk situations than yours. At 40 days (6 weeks) you should have just had a standard abntody test.
You had a low risk exposure that did not warrant testing at all, except as psychological support. If you have had a negative antibody test at least 6 weeks after the event, you need no further testing. If you haven't yet had an antibody test and need thereassurance, do it now. The result will be negative.
HHH, MD
You had a low risk exposure that did not warrant testing at all, except as psychological support. If you have had a negative antibody test at least 6 weeks after the event, you need no further testing. If you haven't yet had an antibody test and need thereassurance, do it now. The result will be negative.
HHH, MD
PCR DNA test are not diagnostic tests. They are not a stand alone test either. There is one PCR test that is a diagnostic test and it's a PCR RNA test. But it too, is not a stand alone test.
Thanks Doc...why do the testing centers (like LabCorp) offering DNA PCR say to wait 28 days, if by that point in time, its not as useful? Wouldn't they want to move up the time frame then? The results are still valid post 28 days - as there would be HIV DNA?
FYI - I did have an antibody test at the exact same time (40 days) - which was negative.
FYI - I did have an antibody test at the exact same time (40 days) - which was negative.
MEDICAL PROFESSIONAL
Because the commercial laboratories and the PCR test manufacturers are promoting the test for a differnent purpose than you used it for. The main use of the test is to monitor the status of someone's ongoing HIV infection, not to diagnose new infections. For that purpose--which as I said above is not recommended in situations like yours--there is no reason to use PCR beyond ~4 weeks, when the antibody tests are positive.
HHH, MD
HHH, MD
One minor correction to Teak's post. While both PCR tests (RNA and DNA) are NOT recommended for diagnostic purposes, of the two, the one used most for diagnosis is the DNA test. It is used to diagnose newborns if their mom was HIV positive (because a newborn will not produce antibodies soon after birth). The RNA test (which is also called a viral load test) is used in the treatment of people already infected and in treatment for HIV. The DNA test is simply a positive/negative test which can detect very small levels of HIV in a person's system.
As noted also, the PCR tests can show a false positive for several reasons and this is the primary reason they are not recommended (along with their expense).
As noted also, the PCR tests can show a false positive for several reasons and this is the primary reason they are not recommended (along with their expense).
Ronnie, you are incorrect.
Gen-Probe Receives FDA Approval for APTIMA(R) HIV-1 RNA Qualitative Assay for Clinical Diagnostic Use
SAN DIEGO, Oct. 5 /PRNewswire-FirstCall/ -- Gen-Probe (Nachrichten) announced today that the U.S. Food and Drug Administration (FDA) has granted marketing approval for the APTIMA(R) HIV-1 RNA qualitative assay. The assay may be used as an aid in the diagnosis of acute and primary HIV-1 infection, and to confirm HIV-1 infection in an individual whose specimen is repeatedly reactive (positive) for HIV-1 antibodies. The assay is the first FDA-approved qualitative nucleic acid test (NAT) for these intended uses.
Gen-Probe expects to launch the assay in November in conjunction with the APTIMA HCV (hepatitis C virus) RNA qualitative assay. Detection of HCV RNA is evidence of active HCV infection. The APTIMA HCV assay may be used to detect HCV RNA in individuals with antibody evidence of HCV infection and evidence of liver disease, individuals suspected to be actively infected with HCV with antibody evidence, and individuals at risk for HCV infection with antibodies to HCV.
"We believe these two new qualitative viral products may fill a small yet important medical niche in the detection of two treatable but potentially life-threatening diseases, especially in light of new CDC guidelines that support increased testing for HIV, and new scientific publications regarding hepatitis C," said Steve Kondor, Gen-Probe's vice president of sales and marketing.
Qualitative assays detect the presence of viral genetic material and give a "yes-no" answer as to whether the target virus is present. In contrast, quantitative assays are used to estimate the amount of genetic material present in a sample. Gen-Probe's new viral products are not approved for quantitative use.
In September, the U.S. Centers for Disease Control and Prevention (CDC) published new recommendations for health care providers that are designed to make voluntary HIV screening a routine part of medical care for all patients aged 13 to 64. The CDC estimated that more than 250,000 Americans are HIV-positive but unaware of their condition, and said that early diagnosis is critical in order for people with HIV to receive life-extending therapy.
A recent article in the journal Hepatology (Vol. 44, No. 2, 2006) illustrated the value of monitoring patients with chronic hepatitis C infection with a highly sensitive nucleic acid test. In the study, independent academic researchers retrospectively tested stored blood samples with an assay identical to the APTIMA HCV RNA qualitative assay. The authors concluded that negative results with this assay were more predictive of sustained virological response (SVR) than were negative results achieved with a less sensitive polymerase chain reaction (PCR)-based assay. According to the authors, SVR is an important endpoint associated with durable eradication of HCV infection and long-term remission, if not cure, of disease.
About Gen-Probe
Gen-Probe Incorporated is a global leader in the development, manufacture and marketing of rapid, accurate and cost-effective nucleic acid tests (NATs) that are used primarily to diagnose human diseases and screen donated human blood. Gen-Probe has more than 20 years of NAT expertise, and received the 2004 National Medal of Technology, America's highest honor for technological innovation, for developing NAT assays for blood screening. Gen-Probe is headquartered in San Diego and employs approximately 900 people. For more information, go to http://www.gen-probe.com/ .
Caution Regarding Forward-Looking Statements
Any statements in this press release about Gen-Probe's expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and are forward-looking statements. These statements are often, but not always, made through the use of words or phrases such as believe, will, expect, anticipate, estimate, intend, plan and would. For example, statements concerning new products, potential regulatory approvals, customer adoption, and results of future R&D studies are all forward-looking statements. Forward-looking statements are not guarantees of performance. They involve known and unknown risks, uncertainties and assumptions that may cause actual results, levels of activity, performance or achievements to differ materially from those expressed or implied by any forward-looking statement. Some of the risks, uncertainties and assumptions that could cause actual results to differ materially from estimates or projections contained in the forward-looking statements include but are not limited to: (i) the risk that new products will not be cleared for marketing in the timeframes we expect, if at all, (ii) the possibility that the market for the sale of our new products, such as our qualitative APTIMA viral products, may not develop as expected, (iii) we may not be able to compete effectively, (iv) we may not be able to maintain our current corporate collaborations and enter into new corporate collaborations or customer contracts, and (v) we are dependent on third parties for the distribution of some of our products. The foregoing describes some, but not all, of the factors that could affect our ability to achieve results described in any forward-looking statements. For additional information about risks and uncertainties we face and a discussion of our financial statements and footnotes, see documents we file with the SEC, including our most recent annual report on Form 10-K and all subsequent periodic reports. We assume no obligation and expressly disclaim any duty to update any forward-looking statement to reflect events or circumstances after the date of this news release or to reflect the occurrence of subsequent events.
Gen-Probe Receives FDA Approval for APTIMA(R) HIV-1 RNA Qualitative Assay for Clinical Diagnostic Use
SAN DIEGO, Oct. 5 /PRNewswire-FirstCall/ -- Gen-Probe (Nachrichten) announced today that the U.S. Food and Drug Administration (FDA) has granted marketing approval for the APTIMA(R) HIV-1 RNA qualitative assay. The assay may be used as an aid in the diagnosis of acute and primary HIV-1 infection, and to confirm HIV-1 infection in an individual whose specimen is repeatedly reactive (positive) for HIV-1 antibodies. The assay is the first FDA-approved qualitative nucleic acid test (NAT) for these intended uses.
Gen-Probe expects to launch the assay in November in conjunction with the APTIMA HCV (hepatitis C virus) RNA qualitative assay. Detection of HCV RNA is evidence of active HCV infection. The APTIMA HCV assay may be used to detect HCV RNA in individuals with antibody evidence of HCV infection and evidence of liver disease, individuals suspected to be actively infected with HCV with antibody evidence, and individuals at risk for HCV infection with antibodies to HCV.
"We believe these two new qualitative viral products may fill a small yet important medical niche in the detection of two treatable but potentially life-threatening diseases, especially in light of new CDC guidelines that support increased testing for HIV, and new scientific publications regarding hepatitis C," said Steve Kondor, Gen-Probe's vice president of sales and marketing.
Qualitative assays detect the presence of viral genetic material and give a "yes-no" answer as to whether the target virus is present. In contrast, quantitative assays are used to estimate the amount of genetic material present in a sample. Gen-Probe's new viral products are not approved for quantitative use.
In September, the U.S. Centers for Disease Control and Prevention (CDC) published new recommendations for health care providers that are designed to make voluntary HIV screening a routine part of medical care for all patients aged 13 to 64. The CDC estimated that more than 250,000 Americans are HIV-positive but unaware of their condition, and said that early diagnosis is critical in order for people with HIV to receive life-extending therapy.
A recent article in the journal Hepatology (Vol. 44, No. 2, 2006) illustrated the value of monitoring patients with chronic hepatitis C infection with a highly sensitive nucleic acid test. In the study, independent academic researchers retrospectively tested stored blood samples with an assay identical to the APTIMA HCV RNA qualitative assay. The authors concluded that negative results with this assay were more predictive of sustained virological response (SVR) than were negative results achieved with a less sensitive polymerase chain reaction (PCR)-based assay. According to the authors, SVR is an important endpoint associated with durable eradication of HCV infection and long-term remission, if not cure, of disease.
About Gen-Probe
Gen-Probe Incorporated is a global leader in the development, manufacture and marketing of rapid, accurate and cost-effective nucleic acid tests (NATs) that are used primarily to diagnose human diseases and screen donated human blood. Gen-Probe has more than 20 years of NAT expertise, and received the 2004 National Medal of Technology, America's highest honor for technological innovation, for developing NAT assays for blood screening. Gen-Probe is headquartered in San Diego and employs approximately 900 people. For more information, go to http://www.gen-probe.com/ .
Caution Regarding Forward-Looking Statements
Any statements in this press release about Gen-Probe's expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and are forward-looking statements. These statements are often, but not always, made through the use of words or phrases such as believe, will, expect, anticipate, estimate, intend, plan and would. For example, statements concerning new products, potential regulatory approvals, customer adoption, and results of future R&D studies are all forward-looking statements. Forward-looking statements are not guarantees of performance. They involve known and unknown risks, uncertainties and assumptions that may cause actual results, levels of activity, performance or achievements to differ materially from those expressed or implied by any forward-looking statement. Some of the risks, uncertainties and assumptions that could cause actual results to differ materially from estimates or projections contained in the forward-looking statements include but are not limited to: (i) the risk that new products will not be cleared for marketing in the timeframes we expect, if at all, (ii) the possibility that the market for the sale of our new products, such as our qualitative APTIMA viral products, may not develop as expected, (iii) we may not be able to compete effectively, (iv) we may not be able to maintain our current corporate collaborations and enter into new corporate collaborations or customer contracts, and (v) we are dependent on third parties for the distribution of some of our products. The foregoing describes some, but not all, of the factors that could affect our ability to achieve results described in any forward-looking statements. For additional information about risks and uncertainties we face and a discussion of our financial statements and footnotes, see documents we file with the SEC, including our most recent annual report on Form 10-K and all subsequent periodic reports. We assume no obligation and expressly disclaim any duty to update any forward-looking statement to reflect events or circumstances after the date of this news release or to reflect the occurrence of subsequent events.
Teak: I stand by my statement:
http://www.medscape.com/viewarticle/448718_8
"Diagnosis of Neonatal HIV Infection
Qualitative DNA PCR assay is the test most often recommended for neonatal diagnosis of HIV infection. However, the sensitivity of the assay during the first month of life is 50%, after which it increases to above 96%.[30] A meta-analysis of 32 studies using DNA amplification by PCR in infants reported 91.6% median sensitivity and 100% median specificity in the early diagnosis of HIV subtype B infection. Improved viral detection was noted for infants older than 1 month.[34] False-positive and false-negative rates of 1.8% were seen. Thus, DNA PCR assay may not definitively diagnose or exclude neonatal HIV infection; it should be followed by a confirmatory PCR test at 30 days of age and then by sequential PCR testing.[34] Reduced assay sensitivity may be seen in non-B viral subtype infections."
Therefore your original statement that PCR DNA tests are not diagnostic tests is false. That was the statement I was referring to.
http://www.medscape.com/viewarticle/448718_8
"Diagnosis of Neonatal HIV Infection
Qualitative DNA PCR assay is the test most often recommended for neonatal diagnosis of HIV infection. However, the sensitivity of the assay during the first month of life is 50%, after which it increases to above 96%.[30] A meta-analysis of 32 studies using DNA amplification by PCR in infants reported 91.6% median sensitivity and 100% median specificity in the early diagnosis of HIV subtype B infection. Improved viral detection was noted for infants older than 1 month.[34] False-positive and false-negative rates of 1.8% were seen. Thus, DNA PCR assay may not definitively diagnose or exclude neonatal HIV infection; it should be followed by a confirmatory PCR test at 30 days of age and then by sequential PCR testing.[34] Reduced assay sensitivity may be seen in non-B viral subtype infections."
Therefore your original statement that PCR DNA tests are not diagnostic tests is false. That was the statement I was referring to.
You can stand by it all you want, you're incorrect. If you would have looked at the link you posted you would have seen that the information was three years old. The FDA approval date for PCR-RNA was October 5th 2006. A PCR-DNA is NOT approved for a stand alone HIV diagnostic test.
If PCR DNA test is not a diagnostic test then why is it even on market(in specialized path labs) for sale. Will it be correct to say that these labs are fooling people? Why do pathologists, microbiologists give it a high regard as a diagnostic test calling it extremely sensitive. On the other hand, its PCR RNA which is not a diagnostic test as it is meant to check the viral load and do not deal in YES/NO answer. It's just so confusing and is there anything which is completely believable about HIV infection(from window period to diagnostic tests). When, we talk about 4th generation tests being almost conclusive at 6 weeks, why can't we have a combination of DNA PCR and antibody test at 6 weeks and get more reliable results. I suppose DNA PCR is more sensitive than P24 antigen test. A P24 antigen test sensitivity varies anywhere from 60-80 % and PCR DNA sensitivity is supposed to be 96% after 28 days. This all is just too varied information and can send anyone's head for a spin. There are too many factors which come along with HIV related information(financial gains for test providers, CYA attitude, mixed information regarding window period, testing strategies). Seems everyone is just exploiting fear of HIV and nobody is really bothered to to give correct/complete information varying from window period to testing strategies. seems everyone has an agenda. Superficially, it looks that everyone cares to bring and end to this disease in the world and working hard but if you go by the actions and information present in ground reality...then only God can help...
A PCR-DNA is used on people that have HIV to monitor their viral load.
The test used to monitor viral load is PCR RNA Quantitative. Teak, really, PCR DNA is used for diagnostic purposes. PCR DNA is a qualitative test and can not quantitate(measure up) the viral load. It just gives a "Yes" or "No" answer. I am no expert and I can not make you forcibly believe but this I honestly believe is the truth from what I have learned.
O_G it is not an approved as a stand alone diagnostic test.
"APTIMA(R) HIV-1 RNA Qualitative Assay" - It seems this is also a qualitative test which gives a "Yes" & "No" answer only and do not check upon the viral load. The only difference that I feel that it has from Qualitative DNA PCR is that it checks for virus in free flowing blood plasma whereas the Qual PCR DNA test checks for virus with the cells. I suppose HIV-1 RNA Qualitative is more sensitive as compared to HIV-1 DNA and can detect an infection even quicket. NAT testing is based on similar technology. Whereas, if you go to specialy testing lab and get a DNA PCR test done, they normally ask you to wait at least 2 weeks for reliable results. I think HIV-1 RNA Qualitative PCR even shortens that window.
Well, yes, indeed a PCR(DNA/RNA)can not be considered conclusive as a stand alone test. It certainly has to be followed by an antibody test as an antibody test is the only gold standard for testing in humans. Again for that, I am not sure if external agendas come into play. Why would NAT testing be considered reliable at 10 days post exposure?? That is also a form of PCR. The blood banks do consider it gold standard...don't they????
I cannot believe I actually read such detailed and intense posts about the uses and merits of various tests (well, I read part of it anyway), lol. Anyway, while I don't know specifically about HIV, a virus is a virus and I'm sure this is the same... My husband has chronic HBV, and his hepatologist uses a PCR DNA (not RNA), test to measure his viral load.
You get a postive result on any viral infection at the blood center, the unit will be tossed and you'll get a letter from the blood bank. A false positive will also get the unit tossed.
There is a reasoning for that too and I would like to take a shot at that. Reason your doctor opts for PCR DNA Quantitative test is because viral load is not always detectable in blood plasma as seen in case of HIV RNA(taking into consideration same thing applies for HBV viral load as well). But, once PCR DNA turns positive it remains positive throughout life. The DNA test does not actually look for virus in blood plasma but in the cells. Earlier in the infection, the virus is detectable in free flowing blood till it infects the cells. That's why RNA qualitative can detect it earlier as compared to DNA Qualitative and that is the reason labs prefer to use DNA test after at least 2 weeks have passed post exposure.
You are right about chances of false positives and the emotional turmil attached with it but what would u make out of a negative PCR test???
Depending on the time I took the test and the risk if I would retest again at a later day. I certainly would not test after the 13 week period.
The fact that my link was two years old is irrelevant. The only purpose of a PCR proviral DNA test is for diagnostic purposes. A PCR RNA viral load test is used in the treatment of HIV positive individuals....
Ronnie, stop giving out false information. PCR DNA is not approved for diagnostic purposes. It is not a stand-alone test. PCR RNA is an approved diagnostic test, but it is not a stand-alone test. You show me on article that states PCR DNA is an approved diagnostic test.
Well, in that case only "APTIMA(R) HIV-1 RNA Qualitative Assay" is FDA approved and not any other PCR RNA also.
That way more than 3/4th of the tests used in the world are not F.D.A approved. Wouldn't you be of the view that FDA approval also got a lot to do with PR BS. I can not comprehend food and drug administration comparing the accuracy rates of 2 PCR tests over a million samples to come up with a clear cut conclusion about which 1 is better and so it should be approved. I know this issue takes the discussion further away from the main topic but what is the basis of approval. Man, I seriously have many issues. I think I just added "trust" to the list. We probably got to check who is a major stock holder in this company and what are his associations in the "u know where".
That way more than 3/4th of the tests used in the world are not F.D.A approved. Wouldn't you be of the view that FDA approval also got a lot to do with PR BS. I can not comprehend food and drug administration comparing the accuracy rates of 2 PCR tests over a million samples to come up with a clear cut conclusion about which 1 is better and so it should be approved. I know this issue takes the discussion further away from the main topic but what is the basis of approval. Man, I seriously have many issues. I think I just added "trust" to the list. We probably got to check who is a major stock holder in this company and what are his associations in the "u know where".
o_g, don't start the conspiracy theories. They got FDA approval because they filed for it to be a diagnostic test and provided their studies.
I think I deserved that comment from you Teak. I am just not a happy person anymore. Me suX!!!!!!
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