HIV is a virus that attacks the immune system, killing immune cells that fight off infection (CD4 cells) so they are no longer able to function. HIV is spread through contact with infected body fluids, including blood and semen.
Today, people who are infected with HIV have access to antiretroviral therapy, a highly effective treatment for HIV that can slow the replication of the virus, improve immunity, and help prevent disease transmission.
The Centers for disease Control and Prevention (CDC) currently recommends screening populations in which at least one out of every 100 individuals (1% risk) are likely to have undetected HIV. Despite this, HIV screening is not routinely practiced in health care settings.
A new study in the February 10, 2005 issue of the
New England Journal of Medicine
used a mathematical model to predict the effects routine HIV screening would have on survival, disease transmission, and cost-effectiveness. The researchers found that the benefits of expanded HIV screening would be worth the costs.
About the Study
The researchers’ model simulated the impact and cost-effectiveness of different HIV screening frequencies (testing one time, every five years, every three years, and annually) in three target populations:
High-risk (3% prevalence of undiagnosed HIV infection)
“CDC threshold” risk (1% prevalence of undiagnosed HIV infection, based on the CDC’s screening recommendation)
“US general” risk (0.1% prevalence of undiagnosed HIV infection, based on the estimated prevalence in the US)
The researchers looked at how HIV screening expansion would affect CD4 immune cell count, quality-adjusted life expectancy, and economic costs.
The model accounted for many potential complicating factors, including whether or not people who test positive for HIV actually receive care and how false-positive test results affect quality of life. It also estimated how many fewer people would be infected as a result of earlier detection and counseling to prevent transmission of the infection to others.
The researchers compared two different types of testing: conventional enzyme-linked immunosorbent assay (ELISA) and the newer same-day, rapid testing.
In the high-risk population (3% prevalence) a one-time screening was associated with earlier HIV diagnosis and a higher CD4 count—210 versus 154 per cubic millimeter with current practice. In this population, the costs of a one-time screening program (e.g., screening, care, counseling, etc.) were $36,000 per quality-adjusted year of life gained. In this same group, testing every five years and every three years cost $50,000 and $63,000 per quality-adjusted year of life gained, respectively.
In the CDC threshold population (1% prevalence), testing one-time, every five years, and every three years cost an estimated $38,000, $71,000, and $85,000 per quality-adjusted year of life gained, respectively.
In the US general population, a one-time screening cost approximately $113,000 per quality-adjusted year of life gained; more frequent testing produced little added benefit.
For people infected with HIV, life expectancy rose as screening became more frequent, from 228 months with current practice to 235 months with annual screening.
ELISA and rapid testing performed similarly in the high-risk population, even though rapid testing is associated with more false positives and their detrimental effects on quality of life. Rapid testing, however, may lead to better outcomes since patients generally receive care more promptly. In the CDC threshold and US general populations, however, higher rates of false positives meant that ELISA “outperformed” rapid testing.
The researchers estimated that, depending on frequency of screening, expanded HIV screening could prevent 300-5,100 secondary transmissions for every 100,000 people in the high-risk population. Expanded screening could also prevent secondary transmissions in the CDC threshold and US general populations, but to a lesser extent.
How Does This Affect You?
These findings suggest that an expanded HIV screening program could facilitate earlier HIV diagnosis, extend the lives of those diagnosed, and reduce the rate of secondary transmissions. Since screening every 3-5 years in populations with a 1% prevalence of undetected HIV or more was considered cost-effective by commonly accepted standards (i.e., a cost below $50,000 per quality-adjusted year of life gained), the authors of this study recommend aggressively expanding and adopting the current CDC recommendations. In addition, they suggest that the benefits of a one-time screening in the general population should be further investigated.
These findings are strengthened by another study in the same issue of the
, which used an entirely different model but produced similar results. This second study estimated that the cost of one-time screening in the CDC threshold population was $41,736 per quality-adjusted year of life gained. The authors of that study came to the same conclusion—that HIV screening should be expanded.
These studies should encourage health care professionals to, at the very least, begin routinely screening higher risk populations for HIV. Since HIV is a deadly, often undetected disease with effective means of treatment, not pursuing expanded HIV-screening aggressively, as the author of an accompanying editorial pointed out, would be “a critical disservice to patients who are currently infected, those at risk for infection, and the future health of the nation.”
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a