A Call for Standardized Outcome Measures

To have a lasting impact on medical science and to change the direction of clinical practice, it is often not enough to have brilliant insight to conduct the perfect study or even demonstrate cause and effect. Clinical practices change very slowly over generations. There are plenty of troubling historical examples of how long it can take for good ideas and sound evidence to begin influencing practice standards.

In 1956, Giles et al.1 reported her findings on epidemiological studies on childhood cancers in Lancet showing that x-rays given to pregnant mothers, a practice that was common at the time, were the cause of these cancers. It was nearly 25 years later that physicians in the United States and the United Kingdom eliminated the routine practice of x-rays for pregnant women. To reinforce how little has changed since then, the October 2017 clinical guidelines on diagnostic imaging during pregnancy from the American College of Obstetricians and Gynecologists currently state the following: “The risk of carcinogenesis as a result of in-utero exposure to ionizing radiation is unclear but is probably very small.”2

Heart disease is currently the leading cause of death in the United States.3 Vascular stents and medications to lower blood pressure have been mainstays of treatment for decades. Nevertheless, studies have repeatedly shown that stents placed in stable patients (those not having myocardial infarctions) do nothing to prevent myocardial infarctions and do not prolong life.4,5 Likewise, millions of patients have been prescribed β-blockers for blood pressure control to mitigate strokes and myocardial infarctions with no good evidence to support this practice. In fact, a Cochrane review published in 2017 on the use of β-blockers for hypertension reviewed results from 13 clinical trials and concluded that other medications were more effective at reducing deaths, strokes, or myocardial infarctions among patients with hypertension.6

It is worth recognizing the barriers to adopting new or revised evidence in clinical practice, and the availability of reliable unbiased evidence is one of the main barriers. Novelty attracts much greater emphasis and reward in biomedical research than reproducibility. Consequently, rigorous studies designed to assess standards that may be deeply embedded in the culture of clinical practice are more difficult to fund and conduct, making it also difficult to raise awareness about clinical outcomes and the need for questions and change. Nevertheless, quality studies that do focus on repeatability and clinical outcomes are a cornerstone of evidence-based practice and an essential part of advancing clinical care.

Cochrane reviews provide a structured methodology for answering questions about clinical practice related to prognosis, diagnostic dilemmas, or any sort of health intervention (medical, surgical, behavioral, etc.). In an ideal scenario, there would be several high-quality randomized clinical trials to evaluate in the context of any clinical question. If one would like to know the comparative effectiveness of topical medications for the treatment of symptomatic dry eye, one could draw on the collective wisdom of unbiased results from multiple trials to arrive at the best answer. If one was interested in the influence of community health screenings on patient motivation to seek further care or the impact of health education programs on health literacy, one could draw on the available evidence to answer such questions. Unlike cancer therapies or cardiovascular interventions, eye care has a much smaller library of randomized clinical trials available to support evidence-based reviews. We are, as a community and as a medical specialty, still in the early stages of maturity regarding the adoption of evidence-based clinical practice standards.

WHERE TO BEGIN?

The outcomes from clinical studies and randomized clinical trials are undermined by the lack of standardization in the results from reported studies. By establishing common outcome measures for a clinical condition, investigators can more efficiently and effectively drive progress through biomedical research. Moreover, their work can contribute to future studies that synthesize common research results in systematic reviews and meta-analyses, but this work can only begin if investigators agree about common measures and use them.

To expand the possibility of conducting high-quality evidence-based reviews, we should collectively encourage the definition and adoption of core outcome sets for the conditions with the greatest public health significance. As of 2018, core outcome sets exist for only three conditions in our field: cataract, glaucoma, and uveitis.7 In November 2017, three additional groups were formed to frame additional core outcome sets for age-related macular degeneration, childhood refractive errors, and dry eye.7 If successful, these working groups would double the number of conditions for which there are standardized core outcome sets, paving the way for future progress in each of these areas.

DEFINING CORE OUTCOME SETS

Standardized outcomes should be relevant to all interested stakeholders, for example, clinicians, patients, payers and policy makers. Typical outcome measures center on clinician-reported outcomes—objective measures of clinical findings (e.g., imaging studies, visual function tests, and laboratory studies) that help clinicians track a patient's condition or response to interventions. Patient-reported outcomes such as discomfort, disability, or dysfunction are also important measures that permit investigators to better understand the unfiltered impact of health, health interventions, and disease on patient quality of life.

Ideally, core outcome sets should:

align with accepted and defensible definitions for the condition and findings; address well-defined, measurable clinical parameters relevant to health outcomes; conform to standardized practices to permit study across health systems; and address relevant concerns for key stakeholders. WHO SHOULD DEFINE CORE OUTCOME SETS?

With several key stakeholders to consider, it is important to think about how to give weight and voice to each of the constituents that should be included in this conversation. One group that is in a unique position to move this conversation forward is the Academic Society. These organizations often have direct connections to universities and institutes. They are typically nonprofit entities with an obligation and regard for public trust. They also can draw together a large body of stakeholders that cut across interest groups: clinicians, patients, and policy makers. Many academic societies also publish peer-reviewed scientific journals. These journals have the responsibility to help define and the authority to enforce the use of core outcome sets.

Although somewhat uncommon, collaboration across academic societies for a common purpose like this could be a powerful and unique opportunity to help facilitate the discussion and definition of common outcome sets. Public agencies, for example, the National Institutes of Health and the U.S. Food and Drug Administration, also play a role in moving the field toward core outcome sets. By facilitating discussions, proposing standards, and defining regulatory guidance, these public agencies have a significant influence on research targets among investigators and a clear obligation to ensure that patient advocates are heard.

WHO SHOULD USE CORE OUTCOME SETS?

Everybody involved in patient care and patient-based research should participate in the discussion, definition, refinement, and wide dissemination of core outcome sets. When core outcome sets exist and are in common use, we will have taken a strong step forward toward embracing outcomes-based care and evidence-based clinical practice. This is a significant step toward a future where clinical practice standards depend less on tradition and opinion and more on evidence and reason. It will take time to change the values upon which we practice, and it will take even longer if we never start.

The cancer and cardiovascular disease examples described previously show how clinicians and their affiliated institutions can be unaffected by high-quality peer-reviewed evidence, but these disciplines are not alone. This is a shared reality that exists, despite the educational practices of our training institutions, requirements for professional continuing education, a wealth of evidence-based literature resources, and academic societies that promote high standards of professional practice. To advance the quality of clinical eye care, we would do well to address core outcome sets focused on the conditions that have the greatest impact on our patient's well-being, our communities, and our health systems.

Michael D. Twa, OD, PhD, FAAO
Editor in Chief Optometry and Vision Science University of Houston College of Optometry Houston, TX

REFERENCES 1. Giles D, Hewitt D, Stewart A, et al. Malignant Disease in Childhood and Diagnostic Irradiation in Utero. Lancet 1956;271:447. 2. Guidelines for Diagnostic Imaging During Pregnancy and Lactation: Committee Opinion No. 723. Obstet Gynecol 2017;130:e210–6. 3. Deaths and Mortality Center for Disease Control. Available at: https://www.cdc.gov/nchs/fastats/leading-causes-of-death.htm. Last updated January 13, 2022. Accessed September 5, 2022. 4. Cruickshank JK. Review: Atenolol May Be Ineffective for Reducing Cardiovascular Morbidity or All-cause Mortality in Primary Hypertension. ACP J Club 2005;142:59. 5. Masoudi FA, Ponirakis A, de Lemos JA, et al. Trends in U.S. Cardiovascular Care: 2016 Report from 4 ACC National Cardiovascular Data Registries. J Am Coll Cardiol 2017;69:1427–50. 6. Wiysonge CS, Bradley H, Mayosi BM, et al. Beta-blockers for Hypertension. Cochrane Database Syst Rev 2017(1):CD002003. 7. Saldanha IJ, Le JT, Solomon SD, et al. Choosing Core Outcomes for Use in Clinical Trials in Ophthalmology: Perspectives from Three Ophthalmology Outcomes Working Groups. Ophthalmology 2019;126:6–9.

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