Is A First Positive For Elisa Test Conclusive?

Posted on Thu, 21 Aug 2014

Question: My boyfriend had rotator cuff surgery yesterday, the doctor nicked his finger while operating. they took blood to run routine test and dr just called to say first test for hiv came back positive, the second and third were negative. how likely is it he is infected? He goes in tomorrow to retest.

Answered by Dr. Sankaranantham Murugan (59 minutes later)

Brief Answer:
False positive result can occur though rare.

Detailed Answer:
Hi,

Welcome to HCM.
Thanks for posting your query.

I can understand your concern about one test positive while the others showed negative.

I would like to know few things:
1. What type of test done for your boy friend. Whether it is a rapid test or ELISA or 4th generation Combo test or PCR TEST?
2.What would be the interval period between these tests?
3. Your boy friend's sexual activities.
These information would help in discussion.
a) Biological false positive or other false positive results were possible with rapid tests, though rare.
b) Certain test antigens are more sensitive and can pick up the antibodies even in lower titre whereas others have a little low sensitivity and show positive after another 15 days or a month.
Anyway the repeat test would be more confirmatory.
Dr S.Murugan

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Sankaranantham Murugan (13 hours later)

It was an Elisa test. First one positive, subsequent two were negative, all tests from same blood drawn that day. He has had only 3 sexual partners in 35 years.

Answered by Dr. Sankaranantham Murugan (2 hours later)

Brief Answer:
More specific test is necessary to confirm status

Detailed Answer:
Hi,
Welcome back.

Technical error and labeling error have to be ruled out.
More specific tests like western blot or Antigen based tests like DNA PCR will be able to either confirm or rule out the HIV status.
Dr S.Murugan

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Above answer was peer-reviewed by : Dr. Vaishalee Punj