How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Dr Uzair Your Own Question
Dr Uzair
Dr Uzair, Doctor
Category: Medical
Satisfied Customers: 9887
Experience:  MBBS, FCPS (R) General Surgery. Years of experience in Emergency Medicine.
Type Your Medical Question Here...
Dr Uzair is online now

How accurate is a combo hiv test antigen and

This answer was rated:

How accurate is a combo hiv test for p24 antigen and antibody at 18 days post exposure. I had a test that came back negative. Although the official guidline from the nhs is 4 weeks post exposure, however quite a lot of stuff on the internet said in a lot of positive cases the antigen would show up early. I realise this is not completely conclusive but wanted to ask how reasuring it is and how accurate at this stage?
Hi and thanks for the query,There is probability of false negative at 18 weeks so you have to wait till 4 weeks. It is too early to comment at this stage, it can go either way but there are 70 to 80 percent chances that you are negative for HIV. but test at 4 weeks would be conclusive.Please do leave a positive rating.Best.
Customer: replied 2 years ago.
ok but just to be clear in majority of cases of hiv positive people would it show up at 18 days? I understand that a lot of people in this scenario would not have antibodies produced in response to the virus until 28 days but the antigen p24 is normally produced from 10 days. since the test looks for both would the antigen not be likely to show up at this stage?
Usually antigen show up from 10 to 15 days but at times it can take longer so we can not say anything with certainity at this stage but a negative test can reassure you a bit.Please do not forget to leave a positive rating.Best.
Dr Uzair and 2 other Medical Specialists are ready to help you