Types of Outcome Measures
From the Desk of Dr. Danielle Meadows,
Vice President of Research Programs & Operations
In an effort to talk a little more about the nuances of the research process, last month I honed in on an aspect of “Study Design, IRB/Ethics Review”: well-powered studies. This month, I want to shift slightly into the “Recruitment, Data Collection” section and focus on outcome measures.
Outcome measures are one of the most important if not the most important aspects of clinical research, as they are the method you use to actually assess a patient’s health status. Given that, outcome measures are, of course, also a critical portion of study design, but I’m categorizing them under this stage as they dictate the data being collected. With how important outcome measures are, I want to spend a little time talking about the different kinds of outcome measures, how these measures can impact the quality of the study, and some examples of outcome measures used in ME/CFS research and OMF projects.
The Heart of the Matter
- Outcome measures are ways of reporting a patient’s health and they fall into four major types: participant-reported outcomes (PROs), clinician-reported outcomes (ClinROs), observer-reported outcomes (ObsROs), and performance outcomes (PerfOs).
- All four types of outcome measures involve some form of human judgment, except for PerfOs, which are objective measurements based on standardized tasks.
- PROs are desirable in clinical research because they provide the patient’s own assessment of their health, but correlating them with objective PerfOs or ClinROs is beneficial.
- OMF’s neuroinflammation study at the Collaborative Center at Uppsala is using both PROs and ClinROs to gain a deeper understanding of the participant’s health and how it correlates to neuroinflammation and microglia activity.
Types of Outcome Measures
Outcome measures are a way of describing how a participant in a research study feels or functions. There are four major types of outcome measures:
- Patient-reported outcomes (PROs): PROs are measures of a patient’s health that are provided directly by the patient without any modification or interpretation by a healthcare professional or other party.
- Clinician-reported outcomes (ClinROs): ClinROs are provided by a healthcare professional and typically require some sort of clinical judgment.
- Performance outcomes (PerfOs): PerfOs are measurements that report results of a standardized task completed by a patient.
- Observer-reported outcomes (ObsROs): ObsROs are measures reported by someone other than the patient or a healthcare professional who is an observer of the patient during their everyday life (e.g., caregiver).
What are practical examples of these outcome measures?
In general, PROs are synonymous with surveys that a participant completes during a study. When we think about ME/CFS, some of the validated PROs that are used in clinical research are: PROMIS-29, SF-36, FUNCAP-55, and DSQ.
ClinROs and ObsROs are similar in that they are measurements that are reported by someone other than the patient. ObsROs are often collected through surveys like PROs and can be particularly relevant for ME/CFS research on pediatric populations or people that are severely ill, where a caregiver may be required to report information on the patient’s behalf. ClinROs, in the context of ME/CFS, might include results from magnetic resonance imaging (MRI) showing neuroinflammation, which requires a clinical interpretation.
PerfOs are unlike the other types of outcome measures in that they are objective, not relying on human judgment. A common example of a PerfO in clinical research is the 6-minute walk test, though a more relevant example for ME/CFS is a cardiopulmonary exercise test.
What types of outcome measures are best for clinical research?
Each type of outcome measure has merits in clinical research, but PROs are often viewed as the most desirable type because they provide the patient’s own assessment of their condition. For example, a clinician might be able to report that a patient is experiencing pain, but only the patient can give an account of the level of pain.
PROs are typically subjective measurements, however, which involve human judgment, so it is important to find a balance between subjective and objective outcome measures to have a more complete and rigorous set of data. Therefore, it’s critical to utilize PerfOs or more objective ClinROs that are specifically designed to measure something likely to be affected by the intervention you’re studying.
Clinical research studies may also use a combination of outcome measures in an effort to correlate subjective measures with those that are more objective. An example of OMF’s work in this area is a neuroinflammation study being conducted by the Collaborative Center at Uppsala. In this project, MRI and other imaging techniques are used to evaluate neuroinflammation and microglia activation in people with ME/CFS. An important aspect of the study, though, are the surveys collected on the day that the participant undergoes the imaging. These data can correlate the imaging results to how the participant is feeling at that time, adding another critical level of understanding to the dataset. To read more about this neuroinflammation project on our website, click here.
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