We found that the cost effectiveness of screening in patients between 55–75 years compares favorably to that of other interventions that are accepted as good uses of resources, particularly if providers implement screening with streamlined counseling and if the person being screened has a sexual partner at risk. Under these circumstances, screening cost less than $60,000 per QALY gained, even with an unidentified prevalence as low as 0.1%. Screening at age 64 years, as recommended by the CDC, cost about $41,000 per QALY gained with streamlined counseling and a partner at risk. Screening is more expensive in patients who do not have a partner at risk, or if traditional counseling is used.
Although evidence about the prevalence of HIV in the older age groups is sparse, the limited available data suggest that the prevalence is sufficiently high for screening to be cost effective. In a blinded serologic survey we performed of 8627 inpatients and outpatients at six Department of Veterans Affairs Health Care Systems, we found the prevalence of undocumented HIV infection was 0.7% (95% confidence interval [CI] 0.2% to 1.7%) in outpatients aged 55 to 64 years, 0.5% (95% CI, 0.2% to 1.2%) in outpatients aged 65 to 74, and 0.1% (0.0% to 0.06%) in outpatients aged 75 and older (157
). Because the VA population differs from that in other health care settings, evidence about the prevalence of undocumented HIV in the over 55 age groups from other populations would be useful to help guide screening decisions. We note however, that among outpatients aged 65 to 74, the prevalence in other settings could be only one-fifth as high as we found and screening with streamlined counseling would still be cost effective for patients who are sexually active.
As noted, an important determinant of the cost effectiveness of screening is whether the screened person has a sexual partner or partners at risk. A recent study used a probability sample of 3005 U.S. adults and found that 73% of people who were 57 to 64 years of age were sexually active, as were 53% of people 65 to 74 years of age, and 26% of people 75 to 85 years of age (161
). The National Health and Social Science Survey in 1992 studied 3,492 members of the US general population and found that 84% of individuals between age 50–54 and 69% of those aged 55–59 had at least one sexual partner in the past year. The National AIDS Behavioral Surveys administered in 1991–1992 estimated that the prevalence of having at least one risk factor for HIV infection was approximately 10% among individuals aged 50 years or older. In addition, a small percentage of those individuals with a known risk for HIV infection used condoms during sex, or had undergone testing and were much less likely to have adopted these prevention strategies than younger individuals who engaged in the same behavioral risks (162
). These studies suggest that a significant number of people over age 50 have risk factors for HIV and that majority of individuals up to age 75 have a partner at risk for infection.
Based on the results of our cost-effectiveness analyses, the data available on prevalence and the relatively high rates of sexual activity in people over age 55, we recommend one-time voluntary HIV screening with streamlined counseling on a routine basis for all persons aged 55–64 and one-time screening on a targeted basis to sexually active persons aged 65–74, if the HIV prevalence is > 0.1%. For people aged 65 to 74 who do not have a partner at risk, screening costs between $50,000/QALY and $100,000/QALY gained with prevalence between 0.1% and 0.5%. Thus, screening is more expensive if the person is not sexually active, but is still a reasonable option, particularly if prevalence approaches 0.5%.
One approach that providers can use to estimate the prevalence of HIV is to begin a screening program, and assess the number of positive tests in the screened population. If approximately 4000 individuals are screened without a positive test, a prevalence of 0.1% can be excluded with 95% confidence, and the population would fall outside the prevalence threshold (0.1%) recommended for screening by the CDC (1
The cost effectiveness of screening remained favorable if HAART were modestly less effective, or led to modestly higher rates of adverse events than in younger patients. An increase in age-specific mortality of 25% in infected patients did not substantively change the cost effectiveness of screening. This finding would not hold for patients whose life expectancy was substantially shortened by diseases with high mortality such as cancer or congestive heart failure. In general, however, our findings support the usefulness of screening older individuals who do not have high-mortality comorbidities if the prevalence of HIV is above 0.1% to 0.5%. Our analysis included three suppressive antiviral regimens before the start of nonsuppressive therapy. With the approval of new antiretrovirals, a fourth suppressive regimen may be feasible, thus we may have underestimated the benefit from antiretroviral therapy in the elderly.
In conclusion, we found that routine HIV screening is cost effective in the age range (up to age 64) and prevalence (greater than 0.1%) recommended by the CDC. If the screened population has an unidentified prevalence of 0.1% or greater, HIV screening in older individuals aged 65 to 75 can also reach conventional levels of cost effectiveness if screening can be done inexpensively, such as by using streamlined counseling. Our analyses suggest that screening decisions in patients over 64 years of age should consider whether there are partners at risk, the expense of screening, and whether there are life-threatening comorbid conditions. Advanced age alone should not preclude screening for HIV. Rather, for many people in this age group, the cost effectiveness of screening falls within the range of other accepted interventions.