Defining outcomes research is not a simple task. Despite its growth over the past several decades, it has been surprising difficult to classify. As noted by some outcomes researchers, the term “outcomes research” is commonly used, but its meaning is less clear [1]. For many of us, outcomes research falls under the larger umbrella of health services research (HSR), primarily because many of the earliest efforts to study outcomes were closely associated with the development of health services research as a discipline. For others without an HSR background, it is more ubiquitous and may have connections to other lines of research such as clinical epidemiology, clinical trials, or more general areas of clinical research miscellany.

Although almost all forms of clinical research include some outcome variable, the editors tend to define outcomes research primarily through the lens of HSR and clinical epidemiology, excluding more general clinical research and clinical trials. Formally defined outcomes research is a form of “health services research that focuses on identifying variations in medical procedures and associated health outcomes [2].” According to the Agency for Healthcare Research and Quality (AHRQ), outcomes research is the primary vehicle to move our understanding of the end results of heath care practices forward and improve the health care system [3]. This general premise is probably consistent with most applied definitions of outcomes research, even if colloquial, and implies a quality objective to improve care, and subsequently outcomes. The spread of outcomes research into the mainstream has also coincided with expansion of its taxonomy. “Outcomes” studies now cover a range of subtopics and distinct but related subareas of clinical research. Research involving population surveys, systematic reviews and meta-analysis, decision analysis, patterns, variation and quality of care studies, quality of life assessment, cost effectiveness comparisons, and the development of prognostic and predictive models all fall under a broad heading of “outcomes” research. Similarly, new avenues in clinical research—in particular comparative effectiveness research and community-based research—will undoubtedly intersect with outcomes research and further expand its application.

For this topic in World Journal of Urology, 12 papers offer a glimpse of the broad but interconnected and often interdisciplinary landscape of outcomes research. While study topics and approaches vary, in whole, this collection of studies provides an instructive sample of the present state of outcomes research. The articles have been structured to illustrate different approaches commonly used in outcomes research, including patient-level studies that utilize patient-reported outcomes, as well as population-based outcome studies. This issue also touches on other topics central to health services and policy research, including assessments of patient preferences and preference-sensitive decision-making, as well as valuation of end of life care. Regardless of the methodological approach or clinical content, each report contributes to a principal question often asked by outcomes researchers, either by defining the extent of a problem and risk factors for poorer outcomes, revealing more effective or efficient practices, or merely by offering an alternative perspective that may not be typically appreciated in most clinical settings; that is, how can we do better?