HIV testing.

Letters to the Editor

Letters to the Editor will be reviewed and are published as space permits. By submitting a Letter to the Editor, the author gives permission for its publication in the Journal. Letters should not duplicate material being published or submitted elsewhere. Those referring to a recent Journal article should be received within 3 months of the article 's appearance. The Editors reserve the right to edit and abridge and to publish responses. Submit 3 copies. Both text and references must be typed double-spaced. Text is limited to 400 words andfewer than JO references. Reprints can be ordered through the author whose address is listed at the end of the letter

Anonymous HIV Testing For their October 1996 paper about the impact of restricted availability of anonymous human immunodeficiency virus (HIV) testing in North Carolina in 1991/92, Hertz-Picciotto et al.1 used data collected by the North Carolina Department of Environment, Health, and Natural Resources. A more rigorous analysis using these data has produced significantly different findings and conclusions.2 I believe that Hertz-Picciotto et al. overstate the adverse impact of restricting anonymous HIV testing and ignore significant adverse impacts of anonymous testing. Advocates of anonymous HIV testing who fail to discuss the existence of adverse effects on public health associated with this form of HIV testing are presenting an unbalanced perspective. Counseling and referral to medical and social resources are critical elements of public health HIV testing services. Anonymous testing reduces the likelihood of optimal posttest counseling and linkage to follow-up services. In addition, several analyses2- have examined the substantially reduced yield of partner notifications associated with anonymous testing. Partner notification is one of the most valuable aspects of public health HIV April 1998, Vol. 88, No. 4

testing programs. When persons who prefer anonymous testing over the confidential mode are diverted from confidential testing because anonymous testing is readily available, there are public health costs associated with that exercise of preference. Hertz-Picciotto et al. also failed to adequately consider other relevant information in the data set they examined. While focusing on the differential growth of anonymous testing in 18 counties offering that option relative to the growth of HIV testing in 82 countries that offered only confidential testing, they did not discuss the implications of the far greater growth of confidential testing in the 18 dual-option countries. When overall testing use increases faster among one population than another, researchers attributing that increase to availability of a single test option must fulfill a standard of proof that has not been met by Hertz-Picciotto et al. D Michael Moser, MD, MPH At the time this letter was written, the author was with the Division of Epidemiology, North Carolina Department of Environment, Health, and Natural Resources, Raleigh, North Carolina. Requests for reprints should be sent to Evelyn Foust, HIV/STD Prevention and Care Section, Division of Epidemiology, North Carolina Department of Health and Human Services, PO Box 29601, Raleigh, NC 27626-0601.

References 1. Hertz-Picciotto I, Lee LW, Hoyo C. HIV testseeking before and after the restriction of anonymous testing in North Carolina. Am J Public Health. 1996;86:1446-1450. 2. Kassler WJ, Meriwether RA, Klimko TB, Peterman TA, Zaidi A. Eliminating access to anonymous testing in North Carolina: effects on HIV testing and partner notification. J Aquir Immune Defic Syndr Hum Retrovirol. 1997; 14:281-289. 3. Hoffman RE, Spencer NE, Miller LA. Comparison of partner notification at anonymous and confidential test sites: HIV test sites in Colorado. J Aquir Immune Defic Syndr Hum

Retrovirol. 1995;8:406-410. 4. Landis S, Schoenbach V, Weber D, et al. Results of a randomized trial of partner notification in cases of HIV infection in North Carolina. NEngl JMed. 1992;326:101-106.

HIV Testing In the annotation' related to our paper2, Rotherman-Borus, while acknowledging the effectiveness of the acquired immunodeficiency virus (AIDS) prevention strategy in Switzerland in regard to increases in condom use, criticizes this strategy for not including advocacy on human immunodeficiency virus (HIV) testing. She bases her argument on a serious factual error: she reports that HIV testing in Switzerland increased from 3% to 4% between 1987 and 1994. The author incorrectly interpreted data from our paper (Table 2) as actual behavior when, in fact, the data represented spontaneous suggestions of means of protection against AIDS. Actually, use of HIV tests is high in Switzerland, even though HIV testing has never been explicitly promoted. In 1992, 47% of the general population 17 to 45 years of age reported having undergone an HIV test (17%, voluntary testing, 24%, blood donation, 6%, both).3 HIV testing was reported more frequently by individuals with several sexual partners. In 1994, 56% of the population 17 to 45 years of age reported ever having been tested.4 Studies in particularly exposed populations show even higher proportions of persons tested. In 1992, 72% of homosexuals reported having been tested.5 In 1993, 87.9% of injection drug users frequenting syringe exchange programs had been tested.6 Data indicate frequent use of anonymous test centers by young people beginning new relationships.7 The high prevalence of tested persons and condom users in Switzerland may be related to the three-level prevention strategy chosen8: prevention campaigns addressed to the population with simple messages (condom use outside stable monogamous relationships, continuing faithfulness, solidarity), targeted prevention addressed to specific groups, and individual counseling by health, educational, or social professionals. Discussion about HIV commonly occurs at the third level: in 1990, 94% of primary care physicians had prescribed at least 1 American Journal of Public Health 683

Letters to the Editor HIV test during the previous 6 months, and 40% had prescribed more than 10 tests.9 In 1992, 72% of the population 17 to 45 years of age visited a physician, and one in seven individuals discussed AIDS, mainly the HIV test.'0 The organization of AIDS prevention activities in Switzerland has permitted extensive diffusion and flexibility of prevention messages. People have access to many complementary sources of information and seem to have made reasonable choices among different options. HIV testing per se is not a primary prevention method. Data on the effect of HIV testing and counseling on protective behavior, especially among HIV-negative individuals, are not conclusive." In general population campaigns, messages should remain the same in order to avoid confusion and maintain widespread protection. However, targeted interventions and individual counseling may now take into account new developments in treatment and encourage individuals who have been exposed to risk to have a test. D

FranVoise Dubois-Arber, MD, MSc The author is with the Institut universitaire de medicine sociale et preventive, Lausanne, Switzerland. Requests for reprints should be sent to Francoise Dubois-Arber, MD, MSc, Institut universitaire de medecine sociale et preventive, Rue du Bugnon 17, CH-1005 Lausanne, Switzerland.

References 1. Rotheram-Borus MJ. Annotation: HIV prevention challenges-realistic strategies and early detection programs. Am JPublic Health. 1997;87:544-546. 2. Dubois-Arber F, Jeannin A, Konings E, Paccaud F. Increased condom use without major changes in sexual behavior among the general population in Switzerland. Am J Public Health. 1997;87:558-566. 3. Jeannin A, Dubois-Arber F, Paccaud F. HIV testing in Switzerland. AIDS. 1994;8: 1599-1603. 4. Dubois-Arber F, Jeannin A, Meystre-Agustoni G, et al. Evaluation of the AIDS Prevention Strategy in Switzerland Mandated by the Federal Office of Public Health. Fifth Assessment Report 1993-1995. Lausanne, Switzerland: Institut universitaire de medecine sociale et preventive; 1997. 5. Bochow M, Chiarotti F, Davies P, et al. Sexual behaviour of gay and bisexual men in eight European countries. AIDS Care. 1994;6: 533-549. 6. Dubois-Arber F, Konings E, Koffi-Blanchard M, Gervasoni JP, Hausser D. Evaluating HIV prevention of low threshold needle exchange programmes in Switzerland. In: Friedrich D, Heckman W, eds. Aids in Europe-the Behavioural Aspect. Berlin, Germany: Ed. Sigma; 1995:183-190.

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7. Rossi I, Jeannin A, Dubois-Arber F, Guex P, Vannotti M. The clientele of an anonymous HIV test centre and the general population tested: similarities and differences. AIDS Care. 1998;1:89-103. 8. Le SIDA en Suisse: 1'epidemie, ses consequences et les mesures prises. Berne, Switzerland: Office federal de la sante publique; 1989. 9. Meystre-Agustoni G, Dubois-Arber F, Gruninger U, Cassis I, Jeannin A. Pratiques et besoins des medecins suisses en matiere de prevention de l'infection VIH au cabinet medical-synthese des experiences: elements de reflexion et recommandations. Schweiz Med Wochenschr. 1995;125:621-626. 10. Dubois-Arber F, Jeannin A, Meystre-Agustoni G. La prevention du SIDA par le medecin: 1'experience des patients. Med Hyg. 1992;50:356-360. 11. Schopper D, Vercauteren G. Testing for HIV at home: what are the issues? AIDS. 1996;10: 1455-1465. Editorial review.

Not All Behavior Change Is Equivalent Dr Fishbein does the public health intervention community a great service by reminding us of the importance of considering the social (or epidemiological) significance of research findings, rather than simply statistical significance.' Consider, for example, two hypothetical interventions for the primary prevention of human immunodeficiency (HIV) infection. Assume that the intent of both interventions is to increase condom use among their respective target populations, PA and PB. Now suppose that intervention A succeeds in raising condom usage from 10% of all occurrences of sexual intercouse to 30%, while intervention B succeeds only in increasing the proportion of protected sexual acts from 15% to 20%. On the face of it, intervention A appears to be much more effective than intervention B, and one can certainly imagine circumstances under which the increased condom use resulting from intervention A-but not from intervention B-would reach statistical

significance. However, suppose that additional information about the two populations, PA and PaB was also available. In particular, suppose that the prevalance of HIV infection was found to be substantially higher in

PB than in PA (e.g., PA might consist of het-

erosexually active men in a small midwestern town and PB of gay men in a large urban center). Because the a priori risk of infection for members of PB~is much greater than the risk for men in PA' it should be clear that whether or not the increase in the proportion of condom-protected acts is statisti-

cally significant is not nearly as important as whether each man reduced his risk of becoming infected by a tangible amount. Thus, from an HIV prevention standpoint, it would be much more relevant to assess the extent of each individual's actual risk reduction rather than simply evaluating changes in condom use behavior. For example, risk could be estimated via the following straightforward formula based on a Bernoulli process model of the sexual transmission of HIV2'3: Risk = 1 - [(1 -I) + iT(l-x)' (l Xt)k]m,

where m is the total number of sexual partners, rr is the probability of selecting an infected partner (which depends on the prevalence of infection in the population), n and k are the numbers of unprotected and condom-protected acts of intercourse (respectively) per partner, x is the probability of HIV transmission per act of unprotected intercourse, and x' is the reduced transmission probability associated with condomprotected intercourse. The difference between preintervention and postintervention risk estimates provides an index of the intervention effect that is directly relevant to the goal of the intervention, namely, preventing the transmission of HIV4 D

Steven D. Pinkerton, PhD Paul R. Abramson, PhD Steven D. Pinkerton is with the Center for AIDS Intervention Research, Department of Psychiatry and Behavioral Medicine, Medical College of Wisconsin, Milwaukee. Paul R. Abramson is with the Department of Psychology, University of California, Los Angeles. Request for reprints should be sent to Steven D. Pinkerton, PhD, Center for AIDS Intervention Research, Department of Psychiatry and Behavioral Medicine, Medical College of Wisconsin, 1249 N. Franklin P1, Milwaukee,WI 53202.

References 1. Fishbein M. Great expectations, or do we ask too much from community-level interventions? Am JPublic Health. 1996;86:1075-1076. 2. Pinkerton SD, Abramson PR. Evaluating the risks: a Bernoulli process model of HIV infection and risk reduction. Eval Rev. 1993;17: 504-528. 3. Pinkerton SD, Abramson PR. The Bernoulliprocess model of HIV transmission: applications and implications. In: Holtgrave DR, ed. Handbook of Economic Evaluation of HIV Prevention Programs. New York, NY: Plenum. In press. 4. Holtgrave DR, Leviton LC, Wagstaff D, Pinkerton SD. The cumulative probability of HIV infection: a summary risk measure for HIV prevention intervention studies. AIDS Behav. 1997;169-172.

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1998, Vol. 88, No. 4