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Comparative Effectiveness Research (CER) and Patient-Centered Outcomes Research (PCOR)

The Institute of Medicine defines comparative effectiveness research (CER), and its purpose, as follows:

"CER is the generation and synthesis of evidence that compares the benefits and harms of alternative methods to prevent, diagnose, treat, and monitor a clinical condition or to improve the delivery of care. The purpose of CER is to assist consumers, clinicians, purchasers, and policy makers to make informed decisions that will improve health care at both the individual and population levels."

The IOM further describes CER as the "direct comparison of effective interventions, the study of patients in typical day-to-day clinical care, and the aim of tailoring decisions to the needs of individual patients".


Another common definition of CER, proposed by Slutsky and Clancy (Am J Med Qual 2009;24:67-70), is the study of "Which treatment works best, for whom, and under what circumstances?" CER may include systematic reviews and meta-analyses, analysis of electronic health records and other databases, and randomized controlled trials.


The introduction of the Patient Protection and Affordable Care Act, and further emphasis on patient and stakeholder perspectives, has subsequently led to defining the related concept of patient-centered outcomes research (PCOR). The Patient-Centered Outcomes Research Institute (PCORI) defines PCOR as research that informs healthcare decisions through answering patient-centered questions, such as:

  1. "Given my personal characteristics, conditions, and preferences, what should I expect will happen to me?"
  2. "What are my options, and what are the potential benefits and harms of those options?"
  3. "What can I do to improve the outcomes that are most important to me?"
  4. "How can clinicians and the care delivery systems they work in help me make the best decisions about my health and health care?"

To answer these questions, PCOR should assess both benefits and harms of interventions, with a focus on outcomes that matter to patients. PCOR should also include a diversity of settings and participants to address individual differences and barriers to implementation and dissemination. PCOR should also be inclusive of individual preferences and stakeholder perspectives.