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HIV screening cost effective regardless of prevalence
Traditional risk factors should no longer be used to determine which patients should be tested.
The controversial questions surrounding routine HIV testing, including who should be tested and how frequently tests should be given, have been answered with a resounding “everyone and everywhere” by researchers at Yale University.
The study finding that rapid HIV testing is cost effective, even in places where only one in 500 people is HIV positive, follows the CDC recommendation in September for widespread, routine voluntary screenings.
“Make HIV testing a part of routine care in all health care settings,” A. David Paltiel, PhD, professor of health policy and administration at the Yale University School of Medicine, told Infectious Disease News. Paltiel and colleagues ran HIV rapid tests under various social scenarios to reach the cost-effectiveness conclusion. The study was reported in Annals of Internal Medicine.
“It is beneficial to make HIV testing a part of routine medical care in just about every population in the United States,” Paltiel said.
Shift changes
The model supports the shift from targeted screening based on risk factors to routine screening based on prevalence and incidence thresholds, according to the study. Reasons for the shift include the blurring of risk group boundaries, the success of antiretroviral drugs and the availability of effective HIV tests.
Clinicians should no longer use risk factors in HIV testing decisions because traditional risk factors are no longer clear, as evidenced by the estimated 250,000 people in the United States who are unaware they are HIV positive, researchers said. Researchers surmised that many people do not know their HIV status because the epidemic is no longer confined to specific risk factor groups.
“So why are we singling them out? It’s stigmatizing and it doesn’t work,” Paltiel said.
Advancement in drug therapy for HIV, the resulting dramatic changes made in survival rates, and prognosis for those infected are another reason HIV tests should be more widely used, researchers said. When tests for HIV were first developed, use of the tests was not widespread among doctors or advocates because it was not clear what would be done with the information. The advent of better drugs removed that part of the question, researchers said.
“Mostly you were identifying the people so you could discriminate against them,” Paltiel said.
Model derived
The Cost-Effectiveness of Preventing AIDS Complications (CEPAC) Model was used to characterize the progress of HIV disease in an infected individual from entry until death. It was then aggregated to simulate clinical courses in individuals and to estimate the average quality-adjusted survival and costs for screening and treatment alternatives, according to the study.
When researchers restricted attention to clinical outcomes affecting only individual patients, current practices of HIV detection produced a discounted daily adjusted life expectancy of 279.91 months. Researchers used randomized trials, observational cohorts, national cost and service utilization surveys, medical management manuals and previous modeling results to conceive and execute the model.
The target population was U.S. communities with low to moderate HIV prevalence defined as 0.05% to 1% to annual incidence of 0.0084%
Outcomes were measured by HIV infections detected, secondary transmissions averted, quality-adjusted survival, lifetime medical costs and societal cost-effectiveness, reported in discounted 2004 dollars per quality-adjusted life year (QALY) gained.
“We show that compared to the other things that we routinely spend dollars on in our country, this confers a substantially better survival and quality-adjusted survival, so there is a bigger bang for your buck,” Paltiel said.
Assuming moderately favorable effects of antiretroviral therapy on transmission, cost-effectiveness ratios remained less than $50,000 per QALY in settings with HIV prevalence as low as 0.20% for routine HIV screening on a one-time basis, and in settings with a prevalence as low as 0.45% and annual incidence as low as 0.0075% for screening every five years, according to the study.
Researchers found that routine HIV screening in a population with HIV prevalence of 1% and annual incidence of 0.12% had incremental cost-effectiveness ratios of $39,800 per QALY for a one-time screening, $32,300 per QALY for screenings every five years and $55,000 per QALY for screenings every three years.
In places where HIV prevalence is 0.10% and incidence is 0.014%, one-time screening produced cost-effectiveness ratios of $60,700 per QALY.
Testing frequency benefit and cost effectiveness over time is still a difficult question, however, because of changing variables.
“It depends on how much HIV you believe there is in a population, how well you think the antiretrovirals work in reducing transmission and how much society is willing to pay for life-saving,” Paltiel said.
False positives considered
Because false positives can occur with any diagnostic test, researchers paid particular attention to the false positive rate for the HIV rapid test when running the design model. The rapid test has a high false positive rate (2.5%) in part because results are given to patients before a laboratory can confirm them. Without a two-week wait for confirmation, however, no patients are lost to followup because results are ready in about 20 minutes.
Researchers estimate that about two per 100 people will be told they were HIV positive in error using the same-day test.
Paltiel said the researchers were concerned about the potential detrimental effects that false positive results may have on a person’s life. Because the consequences can be dire, researchers overcompensated in the model by inflating the false positive sample. They also assumed a large quality of life penalty for a false positive. Despite the social inflation, the model still tipped scales toward more routine testing in cost efficiency.
“We went out of our way to say ‘what if these [false positives] are really big’ and still found that it was worth it,” Paltiel said. – by Kirsten H. Ellis
For more information:
- Paltiel AD, Walensky RP, Schackman BR, et al. Expanded HIV screening in the United States: effect on clinical outcomes, HIV transmission, and costs. Ann Intern Med. 2006;145:797-806.