Patient perceptions of outcome measures in chronic inflammatory demyelinating polyneuropathy: a study of the Inflammatory Rasch-built Overall Disability Scale

Background:
Patients' perceptions of outcome measures used in chronic inflammatory demyelinating polyneuropathy (CIDP) are unknown.

Methods:
We performed a cross-sectional evaluation of patient perceptions of the Inflammatory Rasch-built Overall Disability Scale (I-RODS) from 41 subjects with CIDP through a structured questionnaire. We assessed perceived hesitation to provide a response, item importance and relevance, understanding of specific items and factors affecting responses.

Results:
Hesitation to provide a categorical answer was reported by 20% of subjects or more, for 5/24 (20.8%) items. Uncertainty was most frequent for “travel by public transport” (22.4%) and “catch an object (e.g., ball)” (24%). Six of 24 (25%) items were perceived as unimportant to their disease by at least a third of participants. Items most commonly perceived as unimportant were “travel by public transport” in 53.7%, “catch an object (e.g., ball)” in 61% and “dance” in 65.9%. Several items were frequently perceived as irrelevant. These included “move a chair” (39%), “do the dishes” (46.3%), “catch an object (e.g., ball)” (61%), “travel by public transport” (68.3%) and “stand for hours” (82.9%). The understanding of multiple items such as “read a book”, “sit on a toilet” and “take a shower” was found to be highly variable. Fatigue was perceived more commonly than mood (53.7% vs. 17.1%, p = 0.001), and more commonly in younger subjects (p = 0.037), as influencing responses to the I-RODS.

Conclusions:
Patient-perceived uncertainty, unimportance, irrelevance and poor understanding of items, as well as fatigue and mood, impact on the value of the I-RODS. Greater emphasis on individualized disability assessments requires consideration in future.