POSTING 70: EMPIRICAL DATA ON EFFICACY OF HIV TESTING  


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Frerichs, R.R. Empirical data on efficacy of HIV testing in behavior change.

SEA-AIDS Network, January 26, 1999.

Posted in response to:

SEA-AIDS, January 25, 1999

From David Wilson, Bangkok, Thailand 

Is HIV testing a useful tool for prevention? (I know logic says it should be, but I don't believe it's true).

I have asked this question on this forum before and received replies that support my own experience that HIV testing is NOT useful for prevention. My clinical experience during 15 years in UK, Vietnam and Thailand is that, irrespective of pre-test counselling and psychological support, most people who take a test do so in the expectation that it will be negative. If the result is indeed negative, it confirms that they can continue their previous risky behaviour. If it is positive, they are too shocked to react logically.

This issue is now being discussed again by Professor Frerichs, Rachel Sacks, Graeme Storer and others. Do any readers of this forum know of any peer reviewed publication which proves that HIV testing really leads to change of behaviour in significant numbers of cases?

Dr David Wilson

Medecins Sans Frontieres

311 Ladprao Road Soi 101

Bangkapi, Bangkok 10240, Thailand

R.R. Frerichs Posting

Is HIV testing a useful tool for prevention? This was the question asked by Dr. David Wilson in his recent posting. Wilson goes on to ask, "Do any readers of this forum know of any peer reviewed publication which proves that HIV testing really leads to change of behavior in significant numbers of cases?"

Rather than focus on behavior change per se, I suggest a better outcome measure to answer Dr. Wilson's question is reduced HIV transmission. Thus the hypothesis would be that testing reduces HIV transmission via a change in sexual behavior or blood practices. Once treatment comes into the picture, the potential benefits of testing to induce preventive behavior becomes clouded. Hence the peer reviewed publication that Dr. Wilson is asking for should either be studies done in wealthier countries before 1995-96 when more effective therapy started to appear, or coming from the developing world where treatment is not available.

Most researchers agree that the best proof of a hypothesis comes from randomized clinical trials. In such a trial, the different participating groups should have the same inherent risk of HIV independent of whether or not they received testing. While the information would be useful, doing such a trial would be difficult due to ethical considerations. For example, assume that HIV infected person were identified in a blood testing program in developing country XXX where expensive treatments are not available. Typically in this mythical (but realistic to Southeast Asia) country, blood donors are not told that their blood is infected. To address Dr. Wilson's question, researchers might allocate the detected HIV positive persons to two groups, the "intervention" group that is told of their infection and the "control" group that is not told. The researchers would then follow both groups over time. Because the outcome of interest is further HIV transmission to others, the study would be difficult to do unless the sexual partners were also included, which adds to the complexity and expense of the study. Thus our hypothetical research study might be made more efficient by limiting participants to those who are married. The researchers would then study the spouses of both the HIV infected "intervention" and "control" groups to assess the transmission rate. By now it should be clear to all that such a study would be highly unethical because the researchers would not have informed the "control" group that they were infected and might pass the virus on their loved ones. Thus I doubt that this kind of research study could be done.

Instead of a randomized clinical trial, we more likely need to turn our attention to cohort studies of discordant couples. Here all persons are told that one member of the couple is HIV infected. The researchers can then study the subsequent behavior of the couples and the rate of HIV transmission to see if knowledge of infection which comes from testing had a beneficial effect. Unfortunately with this type of research there is no comparison group under observation. Fortunately, however, comparisons can be made with what occurs in the general society.

The best study of this kind that might answer Dr. Wilson question was published in 1993 by Dr. Alberto Sarracco and colleagues [J Acquired Immune Deficiency Syndrome 6(5)497-502, 1993] and describes the HIV seroconversion experience of 343 steady female partners of HIV infected men in Italy. The HIV transmission rate among those who did not always use condoms was 9.7 per 100 person-years (roughly interpreted as 9.7 percent sero-conversion in one year), and 1.1 per 100 person-years among those who reported always using condoms. A third group among the 343 couples suspended sexual relations with their infected partners. They had no new infections. But did testing lead to preventive behavior change? That is the question that Dr. Wilson is trying to address.

When told that the male member of the couple was infected, 61 percent of the couples either abstained from sex (38 or 11%) or always used condoms (171 or 50%). These two groups are the ones that benefited most from knowing that the partner was infected. Thus it appears that at maximum 61 percent changed their behavior based on the test results and 39 percent did not. Yet without a control group (which would have been unethical), we cannot say for sure what percentage of stable couples would normally have abstained from sex or always used condoms. 

My impression is that few married couples practice abstinence or regularly use condoms (perhaps less than 5 percent). Thus I suspect that the vast majority of the behavior change in the Sarraco study can be attributed to the beneficial impact of testing. Others will have to decide for themselves.

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