May 20th, 2012

News on HIV and HCV Testing, and in Praise of Accurate Screening Tests

Two recent news items reminded me how lucky we are to have some very accurate screening tests for certain infectious diseases.

The news:

  1. An expert FDA panel backed approval of the first true home test for HIV, the OraQuick mouth swab test. Approval of OraQuick for home use may occur later this year. While home testing for HIV exists already — HomeAccess — the OraQuick test will be the first that does not require submitting the specimen to a central laboratory; the user wil be able to get the result at home, much like a pregnancy test.
  2. The CDC is recommending that all Americans born between 1945 and 1965 be tested for hepatitis C. With 1 in 30 from this age group infected, and increasingly effective therapies available now and the near future, this testing strategy (which involves a simple blood test done by a clinician) could dramatically reduce liver-related deaths. (Note that I can’t find this recommendation on the actual CDC site — I know it’s somewhere, but not here or here or here. Oh well.)

Neither one of these tests is perfect, but they’re definitely good enough to be used broadly, with reactive results triggering further testing to confirm or rule out infection. Furthermore, confirmatory tests for HIV and HCV are extremely accurate. In other words, sorting out real HIV or HCV infection from a false-positive screening test is generally quite straightforward.

Now compare and contrast with the disease mentioned in this email query from a primary care provider:

Hi Paul, quick question. 49 year old healthy guy, fatigue and palpitations on and off the past year; normal exam and ECG. Says other people in his neighborhood have Lyme, so I sent the test. ELISA is positive, immunoblot has one IgM band, all IgG bands negative. Could this be Lyme? Should I just give him doxy? For how long?

What did Charlie Brown say when Lucy pulled away the football?

Oh yeah.

5 Responses to “News on HIV and HCV Testing, and in Praise of Accurate Screening Tests”

  1. anonydoc says:

    dear dr. sax,
    wouldn’t you want a hiv test result to be accompanied by a counselling by physician?

    IMHO this is the most problematic aspect of such a test, even more then sensitivity/specifity.

    regards, a.

    • Paul Sax says:

      Dear Anony,

      Given that the vast majority of HIV tests are negative, most (but not all) need little if any counseling when they get their result. By contrast, everyone with a positive test result will need counseling, and presumably this will be done by the provider when they confirm these positive rapid test — tests which really should be considered “preliminary” or “inconclusive” until they’re confirmed.

      As an FYI, I’ve had a couple of patients (literally 2) come my way after testing positive on the HomeAccess test I mention above. Both selected it since it was private and convenient, and neither had a problem with getting their results over the phone.


  2. anonydoc says:

    IMO it would contribute to sexual health to counsel those with negative results as well.

  3. Rod Gordon says:

    This at home test would be perfect for our practice setting in remote northwest Alaska. We serve 15 native Alaskan villages surrounding Nome, and confidentiality is very difficult to obtain when it comes to healthcare, because the village health aide is potentially also a friend or family member. To be able to do this screening test in the privacy of your own home would be a great step forward in helping us screen for HIV. Don’t know if you realize the incidence of Chlamydia and GC here,.. our region leads the state, and our state leads the nation!! Quite an active place to live… for certain things anyway. Guess that’s what happens when you mix cold places and warm bodies! Thanks for covering this topic.

  4. AMoura says:

    Dear Anony, you are right to say that the “optimal” way to go is to provide comprehensive pre and post test counseling. However, remember that “the best is the enemy of the good”.

HIV Information: Author Paul Sax, M.D.

Paul E. Sax, MD

Contributing Editor

NEJM Journal Watch
Infectious Diseases

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