Studying cost-effectiveness

Cost-effectiveness is simply the expression of the amount it costs to prolong someone's life by one year in terms of drugs and medical costs. It does not consider quality of life. It is often used to compare different drug regimens used to treat the same disease.

Quality adjusted life year (QALY) is the measure used to define cost utility. It is calculated by first defining the value which individuals would place on having their health maintained in a particular state by a medical intervention. This will normally be expressed as a numerical value on a sliding scale, and tries to represent the subjective or social value of a particular health-related outcome. This system allows comparison with other disease areas.

Cost-benefit analysis measures all the costs and all the benefits of a particular intervention, and expresses these as the net cost and as a ratio between the costs and benefits. Costs include such measures as lost wages and the value of disability benefits that must be paid, as well as direct medical costs. It also places financial values on different levels of quality of life, taking into account experiences such as chronic pain or serious side-effects. It is considered the gold standard of economic analysis.

Antiretroviral therapy is cost-effective

Clinicians, funders and taxpayers all want to know whether the large sums of money allocated to HIV treatment are worthwhile, albeit for different reasons. US health economists judge that clinical interventions which cost less than $50,000 to $75,000 per life year saved are good value for money. For example, a common intervention for heart disease called ACE inhibitors cost $9700 per life year saved, and is regarded as good value.

A considerable amount of research has been done to investigate the cost-effectiveness of antiretroviral drugs and prophylaxis drugs. The key findings include:

• In patients who start therapy with CD4 cell counts in the 400 to 500 cells/mm³ range, triple therapy with a protease inhibitor costs approximately $10,000 per year of life gained. One study reported that incremental cost per quality-adjusted year of life was $23,000 among patients with advanced disease (average CD4 cell count 87 cells/mm³). Among people with higher CD4 cell counts, incremental costs per quality-adjusted year of life were as low as $13,000 (Freedberg 2001).

• The John Hopkins AIDS Service in Baltimore, United States, surveyed monthly Medicaid payments on HIV inpatient and outpatient services. People with CD4 cell counts below 50 cells/mm³ had unchanged costs ($2629 in 1995, $2585 in 1997). Costs increased for people with CD4 cell counts between 50 and 200 cells/mm³ ($1172 to $1615 monthly) and CD4 counts 201-500 (US$1,078 to US$1,305 monthly). However, inpatient costs of people on protease inhibitors decreased significantly and total health-care costs were lower for people taking protease-containing regimens.

• Another review from between January 1995 and July 1997 from the Veterans Administration Hospital, USA, found that per patient cost decreased from approximately $1900 to $1,120 per month during the study. Number of days inpatient and outpatient visits had dropped by 1997. An update of this study indicated the cost of antiretroviral therapy remained cost-effective into 1999 (Keiser 1999b; Goetz 2000).

• It is estimated that in the United States nearly 35% of the cost of caring for patients with CD4 cell counts above 500 cells/mm³ is attributable to psychiatric illness often related to substance abuse (Moore 1996, 1997).

• A Spanish study found the introduction of protease inhibitors produced an overall saving (due to reduced hospitalisation) of $554,000 in one year (Velasco 1999). American research based on a random sample of 2,864 HIV-infected patients has found costs per patient fell following the introduction of combination antiretroviral therapy (Bozzette 2001).

• A study in British Columbia, Canada, compared treatment cost effectiveness in the eras of dual nucleoside analogue therapy and triple combination therapy. Total costs in 1997 Canadian dollars ($Can)] at 12 months under were $Can 6,620 and $Can 11,914, respectively. Survival at 12 months was 91.0% and 97.6%, respectively. The researchers concluded that cost-effectiveness of HAART was well within the range for other chronic diseases currently funded in Canada (Anis 2000).

• A Swiss study found that HAART increased health-care costs although when productivity costs were incorporated into the analysis, costs were offset for all but the most expensive patients.

• There is preliminary evidence that costs are once again rising. A four-year clinic study found that cost increased in 1997 and 1998, after a substantial drop in cost in 1996 and 1997. The increase was attributed to the rising cost of antiretroviral therapy, more emergency visits and an increasing number of non-HIV-related clinic visits (Keiser 1999). This trend has been confirmed by figures from the San Francisco General Hospital which indicated that total cost of care increases with each treatment failure (Stansell 2000).

Why is antiretroviral therapy cost-effective?

Antiretroviral therapy is undoubtedly expensive, but the cost of not treating HIV infection is greater. Delaying the onset of opportunistic infections and hospitalization by treating people with HAART is more cost-effective than allowing patients to become ill. Opportunistic infections such as MAC and CMV retinitis are extremely expensive to treat, as are drug side-effects such as neutropenia, which occur more frequently in people with advanced HIV disease.

An analysis based on ACTG 320, a comparison of AZT/3TC/indinavir with AZT/3TC, found that treating people with triple therapy over five years would produce a cost saving of about US$5000 compared with dual therapy. The cost saving is the result of the reduced number of opportunistic infections in people on triple therapy. In the longer time, triple therapy is more expensive simply because patients live for a longer time. An estimate of costs at 20 years, suggested that triple therapy with indinavir would cost $13,229 per year, well within the cost-range of other medical interventions (Cook).

Although drug budgets have increased, costs have been dramatically reduced in other areas of HIV care. In some cases the introduction of triple therapy has actually resulted in net savings. However, the most comprehensive reviews of drug costs conducted so far all show that net costs have increased slightly despite large falls in the cost of in-patient care (McCollum; Melnick).

Reduced overall cost has been associated with fewer in-hospital admissions, shorter duration of hospital visits, fewer skilled nursing and hospice days and less home care (Moore; Keiser; Goetz). Statistical analysis found that total cost was inversely related to protease inhibitor usage. Some studies have reported fewer outpatient visits while others have reported an increase. Overall, the fall in inpatient costs has offset any increase in outpatient costs.

References

Anis AH et al. The cost effectiveness of antiretroviral regimens for the treatment of HIV/AIDS. Pharmacoeconomics 18: 393-404, 2000.

Bozzette SA et al. Expenditures for the care of HIV-infected patients in the era of highly active antiretroviral therapy. N Engl J Med 344: 817-823, 2001.

Cook J et al. Modeling the long-term outcomes and costs of HIV antiretroviral therapy using HIV RNA levels: application to a clinical trial. AIDS Res Hum Retroviruses 15: 499-508, 1999.

Freedberg KA et al. The cost-effectiveness of combination antiretroviral therapy for HIV disease. N Engl J Med 344: 824-831, 2001.

Gebo KA et al. Costs of HIV medical care in the era of highly active antiretroviral therapy. AIDS 13: 963-969, 1999.

Goetz MB et al. Effectiveness of highly active antiretroviral therapy (HAART) in veterans affairs medical centers (VAMC) from 1996-1999. Seventh Conference on Retroviruses and Opportunistic Infections, San Francisco, abstract 759, 2000.

Greenhalgh T. How to read a paper no. 8: papers that tell you what things cost (economic analyses). British Medical Journal 315: 7108, 1997.

Keiser P et al. Long-term impact of highly active antiretroviral therapy on HIV-related health care costs. Journal of Acquired Immune Deficiency Syndromes 27(1): 14-19, 2001.

Keiser P et al. Protease inhibitor based therapy is associated with decreased HIV-related health care costs in men treated at a Veterans Administration hospital. Journal of Acquired Immune Deficiency Syndromes and Human Retroviruses 20(1): 28-33, 1999.

McCollum M et al. HAART reduced overall costs of HIV care at VAMC-Denver. Fifth Conference on Retroviruses and Opportunistic Infections, Chicago, abstract 200, 1998.

Melnick D et al. Impact of aggressive management of HIV infection on clinical outcome and costs of care within a health maintenance organisation. Fifth Conference on Retroviruses and Opportunistic Infections, Chicago, abstract 201, 1998

Moore RD et al. Combination anti-retroviral therapy in HIV infection: an economic perspective. Pharmacoeconomics 10: 109-113, 1996.

Moore RD et al. Costs to Medicaid of advancing immunosuppression in an urban HIV-infected patient population in Maryland. J Acquir Immune Defic Syndr 14: 223-231, 1997.

Sendi P et al. Cost effectiveness of highly active antiretroviral therapy in HIV-infect patients. AIDS 13: 1115-1122, 1999.

Simpson KN (ed). Cost effectiveness and AIDS: science or marketing? J Acquir Immune Defic Syndr 10: 1995.

Stansell J et al. Incremental costs of HIV suppression in HIV therapeutic failure. Seventh Conference on Retroviruses and Opportunistic Infections, San Francisco, abstract 761, 2000.

Steinbrook R et al. Providing antiretroviral therapy for HIV infection - Editorial. New England Journal of Medicine 344(11): 844-846, 2001.

Velasco et al. Expenditures for the care of patients with HIV. New England Journal of Medicine 344(25): 1949, 2001.