[Question #331] What exactly are the CDC guidelines for HIV testing.

35 months ago
Good morning DRS. I have a few questions regarding the CDC guidelines for HIV testing.
 What exactly is the window period for testing with just a 3rd generation antibody test in 2015? Is it 3 months or 6months or is the 6months considered out of date, And does that apply to all exposures? I've heard conflicting info on the testing window with most telling me 3months is considered conclusive no matter the test or Exposure. Is the 3 months 84 days or 90 days?
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
35 months ago
Welcome to the forum. Thanks for your question. This is a topic I know something about, as a co-author on CDC's recommendations for routine testing of all patients obtaining health care, without special consent procedures ( 2006 Sep 22;55(RR-14):1-17).

To my knowledge, there are no official CDC guidelines about when to test for HIV after any particular exposure. All CDC's published recommendations are about who should be tested in a general sense:  All pregnant women; all persons age 13-64 at least once in their lifetimes; sexually active persons when evaluated for any STD; and increased frequency of testing (e.g. 1-4 times a year) for people at special risk, such as men who have sex with multiple male partners.

In terms of time after exposure, CDC still tends to stick with a 3 month recommendation, but that's partly from a conservative approach and despite nearly universally accepted evidence that the current (3rd generation) antibody tests detect virtually all infections by 6-8 weeks, and that the duo (4th generation tests for both antibody and p24 antigen) are conclusive any time 4 weeks or more after the last possible exposure. To the extent that some people tend to stick with the older 3 month window, it's hair splitting to distinguish between 84 days (12 weeks) and 90 days (3 months). There are no data on test performance at this level of detail.

I hope that helps. Best wishes and stay safe--  HHH, MD


---
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
35 months ago
I forgot to comment on two aspects of your question. Six months has always been "out of date", at least for 20 years; and most experts now consider 3 months out of date, with rarely any need to go longer. The main exception to both these is after post-exposure prophylaxis (PEP) following a high risk HIV exposure. If PEP doesn't work, it is theoretically possible that the time to valid testing may be delayed. Because there is no clear research on whether this is necessary or how long, people tend to estimate on the high side. Most would still say 3 months is plenty, but I am aware of highly qualified experts to extend that to 6 months. This is one of the major downsides to PEP and a reason it usually should not be used when the risk of exposure is low, especially in people who are inherently anxious:  it prolongs the time of anxiety and uncertainty.

Do all exposures have the same window period? Biologically, yes. However, additional testing is often recommended when the risk is especially high. For example, if the likelihood of infection is, say 1 chance in 10,000, a negative test that is 99% accurate drops the odds of being infected to 1 in a million, which should be sufficient to reassure even the most anxious soul. OTOH, if the risk starts out at say 1% (1 in a hundred), a 99% accurate test drops the chance HIV is present to 1 in 10,000. Still very low and highly reassuring, but perhaps not as good as 1 in a million. Exactly the same test, but different level of reassurance, perhaps warranting another test in a few weeks. There are no formal recommendations along these lines, just common sense approaches used by some experts.

---
35 months ago
Thanks Dr Handsfield. Would the window period for HepB and HepC also be 3 months or would those extend to 6 months with the modern day Antibody tests?
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
35 months ago
I'm not as familiar with test timing for viral hepatitis. Such testing is almost never done after any particular sexual exposure; the risk of infection almost always is too low and I rarely have had need to advise about timing since exposure. For hepatitis B, I believe 6 weeks is fine, hep C a bit longer. Also, hepatitis C is not an STD. The ONLY proved sexual transmission scenario is when gay men participate in potentially traumatic anal sexual practices. The overall frequency of hep C infection is no higher in the lifelong sex partners of people with hep C than it is in the general population, unless the couple also have blood exposure risks like shared injection equipment.

---
35 months ago
Hi Dr my last question involves a Co infection of HIV and HepC and HepB. If a person were infected with HIV along with HepB or HepC would the window period change for the 3rd generation test or would 90 days still cover it? How about the 4th generation test? Thank you for your response.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
35 months ago
Nope. Neither the antibody (3rd generation) or duo (4th gen) HIV test windows is known to change in the presence of hepatitis B or C.

---
35 months ago
Thanks Dr Handsfield! I recently had my 90 day 4th gen HIV test along with HepC, HepB, and Syphillis which all came back Neg. I had a high risk exposure and i'm ready to put it behind me. Thank you for your time and expertise. 
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
35 months ago
You're welcome; glad to have helped. Thanks for the thanks. Stay safe and happy holidays.

---