Value-Based Medicine

Determining the "Value" of Interventions

By Melissa M. Brown, MD, MN, MBA

To date, we have looked closely at the first of the three foundation blocks of Value-Based Medicine: evidence-based medicine. Topics reviewed included the "p-level," the power of a study, the determinants of validity, significance and importance of the evidence defining the efficacy, and safety of the medical intervention, drug or device. We reviewed the issue of risk reduction and identified the differences between absolute and relative risk and how they may be used in the literature.

Defining "Value"

Now, onward to the second foundation block, value — a word often used in different strokes by different folks. Economists commonly define value by referring to money in some form. However, the tenets of Value-Based Medicine define value in terms of providing the medical care that enhances the length and quality of life for our patients. Interventions that do neither should be discarded or improved so they do provide value.

Defining value as such allows us to amalgamate the evidence of efficacy and safety with the value it brings to our patients. Furthermore, it allows comparison of those results in terms of comparative effectiveness. But, be very clear: it is exactly that ability to describe clinical trial results in value terms, including not only efficacy but effects of adverse events, that allows for appropriate comparisons among the clinical data. Once the comparisons are made, costs can always be determined and evaluated per unit of value.

Measuring length of life is relatively straightforward and may be assessed in clinical studies. It is often very clear how many years, if any, a particular in tervention increases survival. However, accurately measuring improved quality-of-life can be more difficult to achieve.

The outcomes in evidence-based clinical trials are typically expressed in scientific terms such as millimeters of mercury to assess blood pressure, IgG antibody titer levels to assess the degree of influenza A immunization or the percentage of obstruction in a carotid artery in a patient with a transient ischemic attack. While these numbers can reveal substantial information about health states and the outcomes of interventions, there are major drawbacks in regard to their applicability for stakeholder groups in health care.

Specifically, these numbers often fail to address the following:

■ An objective measurement of improvement in quality of life. For example, exactly how much does decreasing the diastolic blood pressure from 110 mg Hg to 80 mm Hg improve quality of life? Or how does improving vision from 20/200 to 20/30 improve the quality of life for the average person?

■ A comparison of the quality of life improvement conferred by interventions in disparate specialties. Using the prior example, which is more valuable to a patient: the improvement in blood pressure or the gain in vision?

■ The ability to incorporate data into cost-utility analysis to assess the value conferred by an intervention for the resources expended. If two interventions provide the same value, are they equally desirable? From the therapeutic point of view, yes. But if one intervention costs 40 times the cost of the other, how much should a society with limited resources invest in each of these interventions?

Clearly, measuring the improvement in quality of life and length of life that interventions confer is critically important and relevant. Theoretically, the ideal health-related quality-of-life instrument should be one that is:

► All-encompassing in regard to the variables that compose quality of life

► Sensitive to small changes in health

► Reliable (reproducible)

► Applicable across all of the medical specialties

► Able to be completed within a reasonable time period

► Understandable by patients

► Able to demonstrate construct validity (the ability to measure what is intended to measure)

► Able to be integrated with health care costs for the performance of healthcare economic analyses.

No instrument is ideal, but I believe utility analysis — particularly, time-tradeoff methodology — amply fulfills the criteria above.

In upcoming columns, we will discuss the various methods. However, next issue we will take a break from the basics! I will demonstrate how these data can be useful to the ophthalmologist by showing the tremendous value of cataract surgery. OM

Value-Based Medicine is a registered trademark of the Center for Value-Based Medicine.

Melissa M. Brown, MD, MN, MBA, is president and CEO of the Center for Value-Based Medicine in Philadelphia. She can be reached via e-mail at mbrown@valuebasedmedicine.com.