The Association Between Disability Level and Health-Related Quality of Life in CIDP Patients

OBJECTIVES: Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is a rare autoimmune disorder characterized by distal/proximal weakness and/or sensory deficits. ADHERE is the largest CIDP trial in which efficacy of efgartigimod was demonstrated. The objective was to perform a post-hoc investigation on the association between the disability level and health-related quality of life (HRQoL).

METHODS: ADHERE enrolled N=322 CIDP patients and used the INCAT disability score as the primary outcome (range 0-10). HRQoL was assessed with the EQ-5D-5L, with utility values ranging from 1 (full health) to -1, and 0 corresponding to death. The BPI-SF measured pain severity and interference (range 0-10), HADS assessed anxiety and depression (range 0-21) and RT-FSS was used to measure fatigue (range 0-21). Data from the last observation of the open-label stage was used to estimate Kendall rank correlation coefficients.

RESULTS: A strong negative correlation was found between INCAT and utility value (r=-0.537). This result was mostly caused by the dimensions “Mobility”, “Self-Care” and “Usual Activities” for which strong correlations were observed with INCAT (r=0.581, r=0.559 and r=0.620).

The correlations between INCAT and the scores for “Pain/Discomfort” and “Anxiety/Depression” were weaker (r=0.248 and r=0.256). This was confirmed by the correlation between INCAT and BPI pain severity (r=0.211 ) and interference (r=0.207); and between INCAT and HADS anxiety (r=0.103) and depression (r=0.201). 60% of the patients reported not being anxious or depressed in the EQ-5D-5L. Furthermore, the BPI displayed strong floor effects for its pain severity (30%) and interference domains (38%).

Finally, a positive correlation was found between INCAT and the RT-FSS fatigue score (r=0.211). A ceiling effect for RT-FSS was noted, with 18% of the observations being at the maximal value of 21.

CONCLUSIONS: A higher degree of disability in CIDP patients is associated with lower utility values. This association is mostly explained by the dimensions Mobility, Self-Care and Usual Activities.