To investigate clinically meaningful outcome measures associated with minimum symptom expression (MSE) in a cohort of treated CIDP patients.
Clinically derived endpoints for CIDP reflecting patient function are necessary to optimally assess disease activity and treatment efficacy.
We retrospectively analyzed a consecutive Australian cohort fulfilling 2021-EAN/PNS CIDP criteria1 on therapy between April 2015 and January 2017. Comprehensive assessments of clinical impairment, disability and patient-reported outcomes were performed pre- and post-treatment for patients on cyclic therapy. MSE was systematically defined as an I-RODS score ≥44/48, with no meaningful functional limitation (all activities scored as possible).
Forty-two patients were identified (mean age 57 years; 64% male; median disease duration 8.5 years[range 0.33-45]). Phenotypes were typical (48%), multifocal/focal (24%), distal (12%), sensory/sensory-predominant (12%), and motor-predominant (4%). Treatments included intravenous immunoglobulin (IVIG) (90%), plasma exchange (5%), prednisone (14%), mycophenolate (12%) and azathioprine (2%). Average IVIG regimen was 0.7g/kg, 4 weekly. 21% (8/38) at baseline and 27% (9/33) post-treatment (mean interval 12.4 days) fulfilled MSE criteria. MSE status was not significantly different by age, disease duration, muscle strength (MRC-SS), dominant grip strength (p=0.089), sensory function (mISS), fatigue (mFSS) or pain. Outcomes significantly distinguishing MSE were 10MWT (7.19 vs 9.65 sec, median faster walk 2.37 sec, 95%CI 1.25-3.51, p<0.001) and INCAT (2.5 vs 3, median decrease 1-point, 95%CI 0-2, p=0.026). Logistic regression showed MSE associated with faster 10MWT (OR7.7, 95%CI 1.6–37.0, p=0.011; and lower INCAT (OR 2.3, 95%CI 1.06-5, p=0.036). 10MWT showed excellent discrimination of MSE (AUC 0.93, 95% CI 0.82–1.00, p<0.001) with optimal cut-off ≤6.5 s (sensitivity 0.90, specificity 0.80, p<0.001). Discrimination was fair for INCAT (AUC 0.758, 95%CI 0.603–0.914; p = .001); cut-off ≤2 yielding 63% sensitivity and 73% specificity.
MSE was achieved in 21% of CIDP patients on maintenance treatment, best distinguished by measures of gait (10MWT) and disability (INCAT).