Viewpoint (The Lancet 343, 960-962, April 16, 1994)
Personal Screening for HIV in Developing Countries
Ralph R. Frerichs
The recent article by Mastro and colleagues on female-to-male transmission of HIV-1 in Thailand shows again that surprises should not be surprising when dealing with the human immunodeficiency virus (HIV). Based on a statistical analysis of young Thai military conscripts, Mastro et al. reported that HIV is 30-50 times more infectious for female-to-male transmission than previously estimated. While reasons remain elusive, the authors observed that the higher transmission probability is consistent with national epidemiological patterns of HIV infection. Similar uncertainty over HIV being faced by investigators in Thailand was also voiced in a recent survey of 150 top AIDS researchers.
They noted that new knowledge about HIV is often at odds with old assumptions. This realization should hold true for public health professionals as well, in their attempt to control the deadly HIV epidemic. Rather than assume the correct path is known, health officials must remain open to new thoughts and new programs. Encouraging voluntary and anonymous testing for HIV in the privacy of the home is one such new approach. Given accurate, acceptable, and inexpensive HIV screening tests, what is needed is political will to make tests available in the private sector and to support the evaluation of widespread self-testing as a control strategy.
For people in developing countries, there are three main ways to prevent HIV transmission from an infected partner. First is to assume all sexual partners might be infected and use condoms with every penetrative sexual event. With a slippage and breakage rate of 10 percent, the risk reduction associated with universal condom use would be near 90%, although others have estimated condom effectiveness to be nearer 70%. The promise of such a dramatic reduction in virus transmission has made condoms the intervention method of choice of the World Health Organization (WHO) and other international organizations. The second approach being discussed by many is a vaccine, not yet developed. Even if such a vaccine becomes available, the effectiveness likely would range from 60% shown for the cholera vaccine to 95% exhibited by the measles vaccine. A third method which holds great promise is voluntary home testing. Depending on the sensitivity of the test and the length of the viremic but antibody-negative window period, such testing might reduce risk by 95-99% if people use the information to avoid intercourse with an infected partner. The lowest risk would be experienced by persons who both test their sexual partner and use condoms.
Now that assays are available to accurately detect HIV antibodies in saliva, [7, 8, 9] home testing is the logical next step for persons wanting to protect themselves from HIV. WHO recommends testing of blood donations to avoid transmission, and suggests ways to reduce costs for screening in developing countries. The development of similar low cost testing strategies should be encouraged for preventing spread from an infected sexual partner. Technology already exists to gather saliva specimens at home using special collection devices.[9a] With additional changes in the marketplace, people could send numbered specimens to a local laboratory and receive the results in an anonymous manner within a few days. If cost is reasonable, the screening test could be widely sold in the private sector at pharmacies, food stores, or medical clinics, similar to the distribution network for condoms.
Home testing by its nature would be voluntary and anonymous. Rather than demanding that saliva be evaluated as a diagnostic medium for HIV infection, simple saliva tests should be viewed as screening measures for persons to identify if they or their sexual partners are probably HIV infected. If the saliva test is positive, subjects should be encouraged to go to a medical practitioner for confirmatory testing with blood. Once self-screening is widely being practiced, medical personnel would spend less of their valuable time with HIV negative persons (i.e., the worried well). Home testing would eliminate the need for venipuncture screening facilities and labor-intensive pretest counseling sessions, two components that add greatly to the cost and inconvenience of testing in many developing countries. Instead health officials could spend more of their scarce resources on persons who are actually infected, including diagnostic testing and counseling about treatment and care options, and ways to limit transmission.
Thailand is currently facing a major HIV epidemic, well documented by an innovative sentinel surveillance program. In spite of much technical and financial assistance, the epidemic has continued to confound experts with its persistently rising prevalence levels in most of the sentinel groups. The prevalence of infection in lower class sex workers has risen dramatically from about 5% in June 1989 to over 30% in June 1993. The rise has been equally alarming among males at sexually transmitted disease (STD) clinics and higher-class sex-workers, going from a low of 1-2% to a high of 8-10% during the four years from 1989 to 1993. Finally, the most frightening increase of all has occurred among females at antenatal clinics who exhibited a low prevalence of 0.1% in June 1989 and four years later are edging towards 2% (information from the Division of Epidemiology, Thai Ministry of Public Health). Other recent studies of young men entering the military in the Northern region of Thailand have reported HIV prevalence of 12-15%, supporting the notion that the epidemic is gaining momentum and that existing control strategies are not successful, most notably in the general population. [11, 12]
The rapid expansion of the epidemic has occurred at a time when Thailand has substantial funding and technical assistance to support control efforts. Funds have come from the active national economy and from international donor agencies. Like most government health agencies, the Thais have followed the HIV control suggestions of the WHO and various non-governmental organizations, namely screening of blood, promoting early treatment of sexually transmitted diseases, health education of the public about ways to prevent HIV transmission, sterilization of blood injecting equipment, and promotion and sale of inexpensive condoms, especially to commercial sex-workers [5a, 14] Testing people for HIV antibodies was not considered a desirable option in Thailand, but is done in a limited way by some insurance companies, private practitioners, and a few anonymous testing centers run by the Red Cross and other organizations. As a result, the vast majority of Thai citizens, like most populations in developing countries, have no way of knowing if they or their sexual partners are infected with the virus.
If infection with the HIV-1 strain observed by Mastro and associates occurs before marriage in Thailand, the susceptible partner will soon become infected. Assuming a transmission probability of 0.031 per coital event,[1a] 91 coital events per year, 5% condom use, and a condom slippage or breakage rate of 10%,[3a] There exists a 91% chance that the sexual partner will be infected during the first year of marriage. Of course steps can be taken to avoid becoming infected. Given present policies, the couple in Thailand will likely have no knowledge of each other's HIV infection status. Thus condoms could be recommended for every coital act. Most married Thais, however, do not favor this approach. Only 5% of Thai married couples use condoms on a regular basis (information from the Thai Red Cross and Chulalongkorn University), suggesting that condoms are viewed as both a hindrance to conception and an unnecessary intrusion into the intimacy of marriage.
If inexpensive HIV home tests are available, the couple has another option. They could screen each other for the presence of HIV antibodies and then act on the findings. A screening test should be an important component of partner selection so that marriage can start as a union between two uninfected persons. Such screening would prevent men from marrying HIV infected women who return home after spending several years as a commercial sex worker. It would also prevent women from marrying men who have experimented in their youth with illicit intravenous drugs, anal intercourse with other men, or the services of prostitutes.
Once married, a monogamous woman faces the danger of being infected by her promiscuous or drug-using husband. If he shows signs or symptoms of an STD or fresh needle-marks, she could again quietly screen him at home for HIV or she could insist he always use a condom for sexual intercourse. It is also possible that the act of testing makes both partners more aware that either might become infected and thus, view more favorably the practice of monogamy. What is evident based on the dramatic emerge of the HIV epidemic is that people in Thailand, similar to other developing countries facing HIV, have few alternatives other than premarital screening and monogamy for saving their country from social and economic disaster. It is time to reconsider old ideas and questionable assumptions about what will and will not work. It is time for public health officials in developing counties to join with the private sector and evaluate the cost and effectiveness of home testing for HIV infection.
1. Mastro TD, Satten GA, Nopkesorn T, Sangkharomya S, Longini IMJ. Probability of female-to-male transmission of HIV-1 in Thailand. Lancet 1994; 343: 204-207.
1a. same reference as #1
2. Cohen J. AIDS research: the mood is uncertain. Science 1993; 260: 1254-1255.
3. Trussell J, Warner DL, Hatcher RA. Condom slippage and breakage rates. Family Planning Perspectives 1992; 24(1): 20-23.
3a. same reference as #3
4. Weller SC. A meta-analysis of condom effectiveness in reducing sexually transmitted HIV. Social Science and Medicine 1993; 36(12): 1635-1644.
5. Kallings LO. HIV infection in the nineties. Vaccine 1993; 11(5): 525-528.
5a. same reference as #5
6. Frerichs RR, Seymour E. More on office-based testing for HIV. New England Journal of Medicine 1993; 328(23): 1717.
7. Frerichs RR, Htoon MT, Eskes N, Lwin S. Comparison of saliva and serum for HIV surveillance in developing countries. Lancet 1992; 340: 1496-1499.
8. Frerichs RR, Eskes N, Htoon MT. Validity of three saliva assays for HIV-antibodies. Journal of Acquired Immune Deficiency Syndromes 1994; (In Press)
9. Tamashiro H, Constantine NT. Serological diagnosis of HIV infection using oral fluid samples. Bulletin of the World Health Organization 1994; 72: 1-15.
9a. same reference as #9
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11. Nelson KE, Celentano DD, Suprasert S, et al. Risk factors for HIV infection among young adult men in northern Thailand. JAMA 1993; 270(8): 955-960.
12. Nopkesorn T, Mastro TD, Sangkharomya S, et al. HIV-1 infection in young men in northern Thailand. Aids 1993; 7(9): 1233-1239.
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14. Weniger BG, Limpakarnjanarat K, Ungchusak K, et al. The epidemiology of HIV infection and AIDS in Thailand. Aids 1991; 5 Suppl 2: S71-S85.