Value-Based Medicine

The “QALY” Value of Cataract Surgery

By Melissa M. Brown, MD, MN, MBA

We have defined valuable medical interventions as those that improve the length-of-life and/or the quality-of-life. Measuring that can be tricky! And measuring it well doesn't happen by luck. Most often, determining the improved length-of-life becomes evident in the clinical trial or systematic review of an intervention.

But many methods are used to determine a quality-of-life improvement. What we are looking for is a methodology that is all-encompassing, sensitive to small changes in health, reliable, applicable across all medical fields, understandable by patients, capable of measuring what is intended and, finally, able to be integrated with healthcare costs.

While interest in utility theory started centuries ago in various forms, in 1944 John von Neumann, a Hungarian mathematician, and Oscar Morgenstern, an economist, published their classic text, The Theory of Games and Economic Behavior, on their theory of rational decision-making in the presence of uncertainly. Further work regarding uncertainty, risk theory and preference measurement have subsequently been applied to medicine and healthcare during the late 1960s and 1970s.

While not perfect in its measurement, I believe utility analysis using time-tradeoff methodology does the best job in meeting the criteria listed while assessing the quality-of-life (QOL) associated with a health (disease) state. By convention, a utility of 1.0 is associated with perfect health and a utility of 0.0 is associated with death. The closer the utility to 1.0, the better the QOL associated with a health state, while the closer to 0.0 the poorer the QOL.

Utility assessments have been obtained from physicians, administrators, researchers and the general public, but increasing numbers of researchers believe those obtained from patients are the most valuable. Above all, it is the patients who have the actual disease who can best appreciate the effect it has on the quality of their lives.

A number of methodologies are available to measure utility, including the standard-gamble technique, the willingness-to-pay technique and the time-tradeoff technique. The latter seems to be the most reproducible and valid. With the time-tradeoff method, a patient is asked how many years he or she believes they will live. The patient is then presented with the scenario that he or she could trade an amount of the remaining time of life in return for being rid of a disease. The proportion of time traded subtracted from one yields the utility.

QALYs and Cataract Surgery

This all sounds pretty esoteric but it actually is most relevant to the care we give our patients, not to mention how policymakers may measure our usefulness to individual patients and society as a whole. As an example, the average patient (measured by assessing many patients, not just one or two) with counting finger vision (CF) in the better eye is typically willing to trade approximately 50% of his or her remaining life in return for perfect vision in both eyes. Thus, a patient with a 20-year life expectancy is generally willing to trade 10 years. The resultant utility is 0.50 (1.0-10/20). If a patient is willing to trade two of 10 years, the utility is 0.80 (1.0-2/10).

Utilities are not necessarily static, and improvement of visual acuity, often by interventional therapy, yields an improvement in quality-of-life and hence, in utility as well. The patient with CF vision in the better-seeing eye achieving at least 20/40 vision after a cataract extraction typically improves from a utility of 0.50 to 0.80 — a gain of 0.30 attributed to the surgery.

The duration of improvement appreciated also factors into the examination of utility. If the above patient experiences the benefit for the remaining 20 years of life, there is a total improvement in utility of 6.0 (0.3 × 20) quality-adjusted life years (QALY).

Why do we care? Because not only do our clinical trials tell us that we improve vision in many ways through ophthalmic interventions but we can reliably and accurately measure and thus demonstrate the great improvement in quality-of-life these interventions have for our patients.

If you are not yet convinced of just how relevant utility assessment is, my next column will outline utilities at the different vision levels and we will compare those utilities levels with those in other medical specialties. You will be pleasantly surprised by the comparisons! 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