Consensus Definitions of Disease Activity and Clinical Outcomes in Patients With Chronic Inflammatory Demyelinating Polyradiculoneuropathy

BACKGROUND AND OBJECTIVES: Key terms describing the activity status and clinical outcomes of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) lack standardized definitions. To address the need for uniform definitions, we sought to develop formal consensus-based terminology to define key aspects pertinent to the management of CIDP. METHODS: In April 2025, the GBS|CIDP Foundation International convened a Task Force of 17 international CIDP experts, 2 guest experts from related specialties, and 3 patient representatives. Task Force panels iteratively reviewed, discussed, and voted on proposed definitions for No Evidence of Disease Activity, Relapse, Response, Refractory, Remission, and Residual Symptoms. Relevant literature was reviewed to inform each definition. A modified Delphi approach was used to achieve consensus, defined as a median rating ≥7 on a 9-point scale with ≥80% agreement. Voting included 17 content experts and 3 patient representatives. Guest experts provided nonvoting input. RESULTS: Composite metrics incorporating disability, strength impairment, and patient perception were determined to provide the most sensitive and specific assessment of clinical change in CIDP. Using commonly used clinical outcome measures, including minimally clinically important differences where available, unique definitions were developed for each clinical term. Definitions for No Evidence of Disease Activity, Relapse, Response (minimal, partial, and optimal), Refractory, Remission, and Residual Symptoms were iteratively refined to integrate patient-reported experiences, standardized disability scores, and objective measures of strength impairment, ensuring that each term captured a multidimensional view of disease status. DISCUSSION: The development of consensus-based definitions for key clinical terms in CIDP addresses a longstanding gap in standardizing the assessment of disease activity and treatment outcomes. By combining patient-reported experiences with objective disability and strength measures, the Task Force created comprehensive definitions reflecting the patient experience. The iterative Delphi process ensured broad expert agreement while allowing patient perspectives to inform the terminology. These standardized definitions may improve consistent evaluations in clinical practice, facilitate communication among healthcare providers, and support more robust design and interpretation of clinical trials. Furthermore, the incorporation of composite metrics sensitive to meaningful clinical changes may enhance the ability to detect treatment effects and disease progression, ultimately promoting more precise and patient-centered management of CIDP.