What happens when people refuse to update their beliefs?

Last week I wrote about “treatment as prevention.” Because being treated by a combination of ARV drugs effectively prevents the transmission of HIV from an infected person to his (her) uninfected partner, the idea is that if we were to test as many people as possible, find out who is infected, and offer them ARVs, we could make significant headway in preventing the spread of HIV. In other words, test and treat.

I offered my misgivings about this here, which had mainly to do with cost-effectiveness and offering people a drug that we have yet to convincingly show helps them (rather than their current and future sexual partners). However, it seems that I might have missed something much more basic. What if the people who are tested (and informed that they are HIV-positive) do not believe that they are actually infected with the virus?

Take a look at the figure below and read on:

As part of a study in Malawi, we have tested a sample of young women for HIV using rapid test kits during home-based voluntary counseling and testing sessions. These door-to-door sessions are a very effective method of getting people tested and informing them of their statuses as the refusal rates are very low and the rapid testing procedures are almost 100% accurate.

(The study followed the HIV testing algorithm described in the Malawi Ministry of Health guidelines. If you are interested in the details of testing procedures, you can find them at the end of this post.)

Some months later, different survey teams visited the same individuals and asked them about their subjective beliefs on their chances of being infected with HIV. The figure above shows the distribution of their answers to the question on the likelihood of being currently infected with HIV (on a scale of 1 to 10) among those who had tested positive for HIV during the VCT session, meaning that these respondents were informed that they were HIV-positive by a Malawian nurse, given post-test counseling, and referred to a health clinic.

• Only 45% of the respondents thought that they are definitely infected with HIV.
• Almost as many young women (39%) said that there was ZERO chance that they were infected with HIV.
• The remaining 16% thought their chances of being HIV-positive as somewhere between 30 and 50 percent.

What is almost as perplexing is that we cannot find any baseline characteristics (such as household wealth or highest grade completed) or current indicators (such as achievement scores in math, language, or cognitive skills) that explain the variation in the subjective beliefs among this group of HIV-infected individuals.

Before we get to “test and treat,” we may first need to learn how to “test and convince.”

P.S. After I posted about the possibility of paying people to undergo circumcision for HIV prevention, the debate on banning circumcision in the U.S. has taken off in the Washington Post, the New York Times, and the blogosphere (although it seems that the Santa Monica effort to ban has been abandoned). I guess I know how to call them: I say "subsidize", they say "ban"!

P.P.S. You can find some more detail below about the HIV testing procedures discussed above.

Home-based voluntary counseling and testing was conducted by Malawian nurses and counselors certified in conducting rapid HIV tests through the Ministry of Health HIV Unit HCT Counselor Certification Program. Pre-test counseling, post-test counseling, and referrals to health clinics were conducted according to the study guidelines approved by the Malawian National Health Sciences Research Committee (NHSRC).

The collected blood sample was first tested using a Determine HIV/1-2^TM assay (Inverness Medical, UK). If the test result was positive, then the sample was tested using a Uni-GoId® HIV assay (Trinity Biotech, Ireland). If these two test results were discordant, then the sample was tested with SD BIOLINE HIV 1/2 3.0 assay (Standard Diagnostics, Inc., Korea) for a tie-breaker. Participants who tested positive on the Determine plus either of the other two assays were interpreted to be HIV infected; those testing negative on the Determine or negative on the other two assays were interpreted to be HIV uninfected. Recognizing that HIV-negative participants could be in the window period, they were counseled to be retested after 3 months if they had any risk factors for infection.

All participating individuals provided informed consent at all stages of the study. Additional consent was obtained from parents or legal guardians of all unmarried girls under the age of 18. Informed consent for HIV, HSV-2, and syphilis testing was conducted separately at the time of biomarker data collection.