[Question #3938] Any difference between blood serum and blood plasma

34 months ago
Hello 

Two months (62 days) after an exposure i got the following test at a lab

Antibody antigen AG/AB Combo (abbott architect) SERUM cmia . 

I believe this is a conclusive test. However just to recheck i went to the cdc site and it says  If a person gets a laboratory-based antigen/antibody test on blood plasma less than 45 days after a possible HIV exposure and the result is negative, follow-up testing can begin 45 days after the possible HIV exposure. For all other tests, CDC recommends testing again at least 90 days after exposure to be sure that a negative test result is accurate.

My test was done on Serum while the cdc site says plasma.  Is that the same thing when it comes to testing of hiv? Do i need to test again ? 



Edward W. Hook M.D.
Edward W. Hook M.D.
34 months ago
 Welcome to our forum. I will be glad to comment. The results of your testing at 62 days are conclusive and definitive. The Abbott architect test is a superb HIV antigen/antibody test which provides conclusive results at any time more than six weeks following exposure. Your negative result provides  conclusive results which indicate that you did not acquire HIV. No further testing related to the encounter you mention is needed. 

 I hope that this comment and clarification is helpful to you. If there are any other questions feel free to use you were up two to follow up questions. Take care. EWH
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34 months ago
Dear doctor
Thanks you for your answer but it left  part unanswered. I apologise for not wording my question better I was actually concerned about the plasma vs serum difference.
I was worried because my test says it was done on blood serum while on the CDC website it mentions ag ab 45 days test on blood plasma. CDC uses the word blood plasma in its guidelines for clinics but says simply blood from a vein in the general area if it's website. 
My worry was that my 60day test says it tested for antigen and antigen on blood serum - not plasma.
Is it the same accuracy ( blood serum and blood plasma) when it comes to HIV tests ? I am assuming it's the same when it comes to HIV testing and my test is conclusive  .
Sorry but this thought has been really worrying me.


Edward W. Hook M.D.
Edward W. Hook M.D.
34 months ago
 Sorry that I missed that part of your question.   These tests perform equivalently when used for serum or plasma.  Nearly all HIV blood tests are performed on serum as yours was. In contrast for PCR type tests, the specimen typically used is plasma. There is no difference in how are the tests you had perform when used with either serum or Plasma.Your tests are totally reliable.   EWH---
33 months ago
Thank you. I took another test at 70days . This will be my last one . I have a last question to clear my mind of al doubts.
When CDC says a test is conclusive do they mean 99 percentile of tests are conclusive by 6 weeks.  HAVE YOU EVERY HEARD OR READ ABOUT ANYONE WHO HAS TESTED NEGATIVE AT 10 weeks BUT LATER GONE ON TO TEST POSITIVE?

Edward W. Hook M.D.
Edward W. Hook M.D.
33 months ago
This question is a bit repetitive.  Conclusive means conclusive, not almost (99%) conclusive.  No, I have never heard of, or seen a person whose test became positive after testing negative at 10 weeks.  Please relax and move forward without concern.

this is my 3rd response your questions.  As per Forum guidelines it will be closed without further comments in a few hours.  EWH
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