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Value Health. 2017 Jul - Aug;20(7):838-855. doi: 10.1016/j.jval.2017.05.015.

Patient-Reported Outcome and Observer-Reported Outcome Assessment in Rare Disease Clinical Trials: An ISPOR COA Emerging Good Practices Task Force Report.

Author information

ICON Commercialisation and Outcomes, Gaithersburg, MD, USA. Electronic address:
Evidera - Evidence, Value & Access by PPD, Bethesda, MD, USA. Electronic address:
Department of Health Services, University of Washington, Seattle, WA, USA.
Pharmaceutical Health Services Research, School of Pharmacy, University of Maryland, Baltimore, MD, USA.
Director, RareAccess Ltd., London, UK.
School of Pharmacy, University of Maryland, Royal Oak, MD, USA.



Rare diseases (RDs) affect a small number of people within a population. About 5000 to 8000 distinct RDs have been identified, with an estimated 6% to 8% of people worldwide suffering from an RD. Approximately 75% of RDs affect children. Frequently, these conditions are heterogeneous; many are progressive. Regulatory incentives have increased orphan drug designations and approvals.


To develop emerging good practices for RD outcomes research addressing the challenges inherent in identifying, selecting, developing, adapting, and implementing patient-reported outcome (PRO) and observer-reported outcome (ObsRO) assessments for use in RD clinical trials.


This report outlines the challenges and potential solutions in determining clinical outcomes for RD trials. It follows the US Food and Drug Administration Roadmap to Patient-Focused Outcome Measurement in Clinical Trials. The Roadmap consists of three columns: 1) Understanding the Disease or Condition, 2) Conceptualizing Treatment Benefit, and 3) Selecting/Developing the Outcome Measure. Challenges in column 1 include factors such as incomplete natural history data and heterogeneity of disease presentation and patient experience. Solutions include using several information sources, for example, clinical experts and patient advocacy groups, to construct the condition's natural history and understand treatment patterns. Challenges in column 2 include understanding and measuring treatment benefit from the patient's perspective, especially given challenges in defining the context of use such as variations in age or disease severity/progression. Solutions include focusing on common symptoms across patient subgroups, identifying short-term outcomes, and using multiple types of COA instruments to measure the same constructs. Challenges in column 3 center around the small patient population and heterogeneity of the condition or study sample. Few disease-specific instruments for RDs exist. Strategies include adapting existing instruments developed for a similar condition or that contain symptoms of importance to the RD patient population, or using a generic instrument validated for the context of use.


This report provides state-of-the-art solutions to patient-reported outcome (PRO) and observer-reported outcome (ObsRO) assessments challenges in clinical trials of patients with RDs. These recommended solutions are both pragmatic and creative and posed with clear recognition of the global regulatory context used in RD clinical development programs.


clinical outcomes assessment; clinical trials; instrument development; rare diseases

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