Thoughtful curation and cataloging of individualized clinical outcome assessments (COAs) tailored to individual genetic variant, natural history and phenotype within the context of broader disease is central to N-of-1 trials.

Outcomes typically span: (1) symptom intensity and frequency, (2) functional status and performance (mobility, activities of daily living, disease-specific function scales which are developmentally appropriate), (3) patient-reported outcomes and quality of life, (4) objective biomarkers and electrophysiologic measures (cerebrospinal, EEG, wearable-derived metrics), (5) adverse events and tolerability (side-effect checklists, discontinuation thresholds), (6) preference and goal attainment (patient-prioritized endpoints, global impression of change).  Increasingly, digital tools also enable high-frequency, low-burden data capture, improving power within individuals, and facilitating Bayesian or hierarchical analyses that can later aggregate across patients. When outcomes are prespecified, reliable, and aligned with what matters to the patient and disease, n-of-1 trials can transform clinical ambiguity into actionable, individualized evidence. Normative data can be utilized, and natural history data can provide additional context, in addition to patients serving as their own controls.

The focus of the Clinical Outcomes Workgroup is to provide guidance in structuring clinical outcomes for n=1 trials across therapeutic modalities and disease contexts.