Although the U.S. Preventive Services Task Force is the most widely respected, unbiased organization producing evidence-based guidelines today, it isn't perfect. In 2002, the USPSTF recommended that women take aspirin to reduce their risk for heart attacks; later randomized trial evidence showed that aspirin only prevents heart attacks in men (it prevents strokes in women). More famously, the USPSTF once overestimated the benefits and underestimated the harms of mammography in women in their 40s, resulting an an apparent about-face in breast cancer screening recommendations in 2009 that made a great deal of political hay. This is the second of two posts explaining the reasons that I think the Task Force got it wrong when it recently endorsed screening all persons ages 15 to 65 years for HIV regardless of risk status. The first post is available here.
Potential Harms and Competing Priorities
Potential harms of HIV testing include false positive results, anxiety, labeling, and adverse medication effects. True positive HIV results can be stigmatizing and lead to discrimination, loss of employment, verbal abuse, and physical assault in 1 to 4 percent of patients (18). A new HIV diagnosis does not seem to be associated with increased partner violence or dissolution of partner relationships in observational studies (18). Adverse effects of highly active antiretroviral therapies are less common today than in previous years, with more treatment options and simplified dosing schedules (19).
Although the overall magnitude of harms related to testing is thought to be small, the USPSTF judged in its 2005 guideline that the modest benefits of routinely screening persons without risk factors for HIV did not necessarily outweigh them (6). Furthermore, HIV testing does not occur in a clinical vacuum, but competes for time in the typical medical visit with many other pressing preventive, chronic, and acute care issues (20, 21). In medical practices that are not part of integrated health systems, the decision to implement or not implement routine opt-out screening for HIV may come down to individual clinicians’ judgments about the uncertain yield of such testing in their population versus competing clinical priorities. Or, as one author has argued: “It would be appropriate for those who want to prioritize preventive services based on proven benefits to adopt the USPSTF recommendation and individualize decisions about HIV screening of low-risk patients. … For clinicians who place a high value on potentially reducing HIV incidence and are more willing to accept plausible but unproven benefits, it might be reasonable to adopt the CDC recommendations” (9).
Altering the Balance of Benefits and Harms
Since the publication of the USPSTF guideline in 2005 and the CDC guideline in 2006, there have been important advances in HIV care that likely increase the relative benefits of universal screening. The improved tolerability of current HAART regimens, combined with evidence from observational studies that earlier initiation of HAART (rather than delayed initiation below a certain CD4 cell count) reduces mortality, led the Department of Health and Human Services to recommend treatment of all patients with CD4 counts below 500 cells/mm3, and to consider treatment for patients with higher CD4 counts (22). If earlier treatment of asymptomatic persons with HIV improves health outcomes compared to delayed treatment, then the benefits of earlier HIV detection through screening will be magnified.
In addition, a recent randomized controlled trial confirmed the benefits of HAART in reducing the risk of HIV transmission to sexual partners (23). This multicenter trial enrolled 1750 HIV-discordant heterosexual and male homosexual couples in sub-Saharan Africa, Asia, Latin America and the United States. All HIV-infected patients had a CD4 count of 350 to 550 cells/mm3 at baseline. In this trial, antiretroviral treatment of HIV-infected partners substantially reduced the incidence of seroconversion in uninfected partners, yielding a rate ratio of 0.04 (95% confidence interval, 0.00-0.27) (23). Even if patients with HIV do not change their sexual behaviors after being diagnosed, this study highlights the value of early diagnosis and initiation of HAART to reduce viral transmission – another reason to believe that expanded screening could yield population-level benefits.
In summary, this comparison of the effectiveness of targeted (risk factor-based) and universal (routine opt-out) screening for HIV has highlighted multiple areas of evidence relevant to determining the optimal approach in the U.S. Provided that most persons who are offered HIV screening accept it, and that persons newly diagnosed with HIV subsequently modify high-risk behaviors to reduce viral transmission, the CDC’s recommendation for routine opt-out screening of adolescents and adults appears to be cost-effective. However, studies of opt-out screening performed in emergency department settings have thus far yielded disappointing results, identifying few new cases of HIV in persons without known risk factors, many of whom were diagnosed in symptomatic or late stages of disease. Harms of HIV screening are small, but may not necessarily outweigh benefits in low-risk populations. Finally, evidence that earlier initiation of HAART improves individual health outcomes and is highly effective at interrupting viral transmission has increased the relative benefits of HIV screening. Based on existing data, then, a routine opt-out screening approach such as that endorsed by the CDC is warranted in high-prevalence clinical settings; however, pending further studies, a risk factor-based approach such as the USPSTF’s is still reasonable in average or low-prevalence settings.
18. Chou R, Huffman LH, Fu R, Smits AK, Korthuis PT. Screening for HIV: a review of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2005;143:55-73.
19. Reust CE. Common adverse effects of antiretroviral therapy for HIV disease. Am Fam Physician 2011;83:1443-51.
20. Pollack KI, Krause KM, Yarnall KS, et al. Estimated time spent on preventive care services by primary care physicians. BMC Health Serv Res 2008;8:245.
21. Yarnall KS, Pollack KI, Ostbye T, et al. Primary care: is there time enough for prevention? Am J Public Health 2003;93:635-41.
22. Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. U.S. Department of Health and Human Services. October 14, 2011; 1–167. Available at http://www.aidsinfo.nih.gov/ContentFiles/AdultandAdolescentGL.pdf.
23. Cohen MS, Chen YQ, McCauley M, et al. Prevention of HIV-1 infection with early antiretroviral therapy. N Engl J Med 2011;365:493-505.