PC-CIS Terminology



Core Outcome Set

Formal definition: A core outcome set (COS) is an agreed standardized set of outcomes that should be measured and reported, as a minimum, in all clinical trials in specific areas of health or health care. 

Source: The Core Outcome Measures in Effectiveness Trial’s (COMET’s) website,


Formal definition: The aspect of an individual’s clinical, biological, physical, or functional state, or experience that an assessment is intended to capture (or reflect). 

Informal definition: The specific “thing” you want to measure, based on what patients report as important to them.



Formal definition: One of several sub-concepts measured individually by an instrument that also measures the general concept that is defined by those domains.

Informal definition: One of the components of a measurement score that is made of up multiple scores. For example, health-related quality of life is a multi-domain concept that represents the patient’s perception of the impacts of illness and treatment on the domains of physical, psychological, and social aspects of life. Each of these is considered a domain.

Source: FDA PROM Guidance Glossary


Formal definition: A precisely defined variable intended to reflect an outcome of interest that is statistically analyzed to address a particular research question. A precise definition of an endpoint typically specifies the type of assessment made, the timing of the assessment, the assessment tool used, and possibly other details, as applicable, such as how multiple assessments within an individual over time are to be combined.

Informal Definition: How meaningful change in a score will be measured and defined in specific study circumstances.



Formal definition: A conclusion that the level of validation associated with an assessment (i.e., biomarker or Clinical Outcome Assessment) is sufficient to support its proposed use.

Informal definition: The measure is the right one considering where, how, and the way it will be used.



Formal definition: Any effect from a disease or treatment on a patient’s health and/or daily life that is reported by patients as important to them. Impacts can include health outcomes as well as things like financial and career consequences, and caregiver and family burden. Impacts might also reflect carer and family views.

Informal definition: Any general effect from a disease or treatment on a patient’s health and/or daily life that is reported by patients as important to them.

Source:  Perfetto, E.M., Oehrlein, E.M., Love, T.R. et al. Patient-Centered Core Impact Sets: What They are and Why We Need Them. Patient (2022).


Formal definition: A means to generate a score that represents a concept plus all the information and documentation that supports its use. Generally, that includes clearly defined methods and instructions for administration or responding, a standard format for data collection, and well-documented methods for scoring, analysis, and interpretation of results in the target patient population.

Informal definition: The tool used to measure a specific thing (or concept). Also referred to as an instrument, or questionnaire.

Source: FDA PROM Guidance Glossary

Mixed Methods Research

Formal definition: Research that uses both qualitative and quantitative research methods. See definitions for qualitative and quantitative research methods.

Source: the BEST Glossary


Formal definition: The change in a concept attributable to an intervention (e.g., a treatment). The measurable characteristic (e.g., survival, clinical outcome assessment, biomarker) that is influenced or affected by an individuals’ baseline state or an intervention as in a clinical trial or other exposure.

Informal definition: The change measured over time in relation to the use of an intervention or to an event.


  • Donabedian, Avedis. “Evaluating the quality of medical care.” The Milbank memorial fund quarterly 44.3 (1966): 166-206.
  • PFDD Glossary
  • The Core Outcome Measures in Effectiveness Trials (COMET) COMET Handbook


Formal definition: Someone having or at-risk of having a medical condition(s), whether or not they currently receive medicines or vaccines to prevent or treat a disease. They are dependent on the health care system after the diagnosis of a medical condition or disability. A patient relies on the health care system to feel better and to have a longer, healthier, and more robust life. An individual patient’s views on health issues, such as the benefit and risk of new treatments, will vary depending on the severity of their condition and personal circumstances.

Source: NHC Patient Engagement Glossary

Patient-Centered Core Impact Sets (PC-CIS)

Formal definition: A PC-CIS is a patient-derived and -prioritized list of impacts a disease and/or its treatments have on a patient and their family and caregivers.

Source: article from The Patient

Patient Engagement

Formal definition: Refers to “the active, meaningful, authentic and collaborative interaction between patients and other stakeholders across all aspects of the health ecosystem, where decision-making with regard to an activity or process is guided by patients’ contributions as partners, recognizing their unique experiences, values and expertise.” This definition is also applicable across stakeholders and engagement activities (e.g., participation in an interview, focus group). 

Source: NHC Patient Engagement Glossary

Patient Experience Data

Formal definition: Defined in Title III, section 3001 of the 21st Century Cures Act, as amended by section 605 of the FDA Reauthorization Act of 2017 (FDARA)1, and includes data that are collected by any persons and are intended to provide information about patients’ experiences with a disease or condition. Patient experience data can be interpreted as information that captures patients’ experiences, perspectives, needs, and priorities related to (but not limited to): 1) the symptoms of their condition and its natural history; 2) the impact of the conditions on their functioning and quality of life; 3) their experience with treatments; 4) input on which outcomes are important to them; 5) patient preferences for outcomes and treatments; and 6) the relative importance of any issue as defined by patients.

Source: FDA PFDD Glossary

Patient Preference Information (PPI)

Formal definition: Assessments of the relative desirability or acceptability to patients of specified alternatives or choices among outcomes or other attributes that differ among alternative health interventions. The methods for generating Patient-Provided Information (PPI) may be qualitative, quantitative, or mixed methods.

Source: FDA Guidance on Patient Provided Information (PPI) for medical devices

Qualitative Research Methods

Formal definition: Methods associated with the gathering, analysis, interpretation, and presentation of narrative information (e.g., spoken or written accounts of experiences, observations, and events). Qualitative research methods may also include direct observations (e.g., non-verbal communication and behaviors). 

Source: FDA PFDD Glossary

Quantitative Research Methods

Formal definition: Methods associated with the gathering, analysis, interpretation, and presentation of numerical information.

Source: FDA PFDD Glossary







Formal definition: A sufficient number of and types of people are included in the engagement activity to ensure that those engaged can speak on behalf of the target population. It refers to “who” and “how many” individuals to include in an interaction in order to, as closely as possible, engage with individuals that represent the broader, target patient population.

Source: NHC Patient Engagement Glossary

Test, Tool, or Instrument

Formal definition: An assessment system comprising three essential components: 1) materials for measurement; 2) an assay (i.e., for biomarkers) or method or procedure (i.e., for Clinical Outcome Assessments) for obtaining the measurement; and 3) method and/or criteria for interpreting those measurements.

Source: the BEST Glossary