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What is the difference between PCR RNA test and TMA RNA test done for HIV?

Answered by
Dr.
Dr. S. Murugan

HIV AIDS Specialist

Practicing since :1974

Answered : 2762 Questions

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Posted on Fri, 8 Aug 2014 in Sexually Transmitted Diseases
Question: Hi Doctor,

What is the difference between PCR RNA test and TMA RNA test for identifying the HIV infection as early as possible?

Which of these is accurate and what is the window period after possible exposure should one wait to get these tests done?

What does a positive result and a negative results indicate in these tests.

Thanks!
doctor
Answered by Dr. S. Murugan 1 hour later
Brief Answer:
PCR RNA to diagnose HIV,TMA RNA assess prognosis

Detailed Answer:
Hi,
Welcome to HCM.
Thanks for posting your query.

HIV RNA PCR is a quantitative test to measure the viral load as so many copies per a given quantity of the individual's blood. It is more useful to assess the prognosis of the disease during treatment naive or on ART.

TMA RNA test is a qualitative test useful to find HIV or to confirm HIV disease. It is more less 99-100% specific and detect the virus 6- 7 days earlier than a P24 Antigen test. So it has a high diagnostic value whereas PCR RNA has more a prognostic value.
Dr S.Murugan
Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
doctor
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Follow up: Dr. S. Murugan 11 minutes later
Hi Doctor,

Thank you for your reply.

Will it be good to take the TMA RNA test after 15 days of possible exposure?
Is there a chance of false negative or false positive in this test?

I was involved in breast sucking in a strip club and put a finger inside vagina only once of a masseuse before 15 days. After those encounters, I am having sore throat, I developed mouth ulcer, little muscle pain on the left shoulder and feeling worried and dizzy. It all seems like the symptoms of ARS. I also developed one or two rashes on my leg and hand.

Please let me know if some one can get infected by HIV through breast sucking (of a non-lactating woman) and fingering a woman (I had a small peel of the skin near the cuticle)?
Am I a candidate for TMA RNA test on 16th day of the exposure?

Thanks!
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Follow up: Dr. S. Murugan 5 hours later
Also, please let me know whether taking a glass of alcohol (margarita) before 18-19 hours of blood sample collection will affect the outcome of TMA RNA test?
doctor
Answered by Dr. S. Murugan 2 hours later
Brief Answer:
Symptoms not necessarily related to HIV.

Detailed Answer:
Hi,
Welcome back.
TMA RNA Test will definitely able to detect HIV antigen as early as 7 days on wards in the presence of any HIV infection. But in certain occasions, the antigen in blood circulation would not be in a detectable quantity till 3-4 weeks and there might be a false negative result. So it is better to have the test after 3 weeks to get a more conclusive test.
Alcohol consumption before 18 hours would not interfere with the result.
Earliest HIV manifestations can occur only after 4-6 weeks after the high risk contact, in presence of a HIV infection. Anything earlier than this period could not be due to HIV. Sore throat, mouth ulcer, body pain can occur to any one without any HIV infection. So your symptoms are not related to HIV. Sucking non-lactating breast has no risk for HIV. Fingering has negligible risk.
Nothing to worry.
Dr S XXXXXXX
Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
doctor
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Follow up: Dr. S. Murugan 11 hours later
Hi Doctor,

Thank you for your clarifications and it really really helped me to get out of fear.

Anyways I had already given my sample for TMA RNA test yesterday (15th day after exposure) as I thought I was getting ARS related symptoms within first 15 days of exposure. Now, after reading your words, I am confident that it will come out in my favour and I will not be HIV infected. Your words on consuming alcohol before 18-19 hours of sample collection would not interfere in the test result, now I am totally relieved from the worries I was going through for the past 2 weeks.

Can I consider the TMA RNA test result if comes out as Negative as a conclusive result in my case?

Thanks!
doctor
Answered by Dr. S. Murugan 4 hours later
Brief Answer:
RNA test rules out commonest HIV 1 not HIV 2.

Detailed Answer:
Hi,
Welcome back.
I will consider TMA RNA test after 3 weeks would be more conclusive than a test after 15 days.
Moreover this TMA RNA test can rule out HIV infection only which is 99% common among HIV disease. A rare possibility of HIV 2 could be ruled out by an antibody test done after 12 weeks to get a more conclusive report. RNA test detects only HIV 1 antigen.
The term 'ARS' is not used now a days. The earlier manifestation of HIV disease is called either as Primary or Acute infection or Sero- conversion illness. It could occur after 4-6 weeks if there is any infection.
Dr S.Murugan
Above answer was peer-reviewed by : Dr. Vinay Bhardwaj
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