Determining the Minimal Important Difference of EQ-5D-5L Utility Values in CIDP Patients Using Data From a Large Clinical Trial
Author(s)
Febe Marloes Brackx, Ir, MSc1, Lucas Van de Veire, MA1, Clémence Arvin-Berod, PharmD2, Sandra Paci, PhD3, Glenn A. Phillips, PhD4, Sarah Dewilde, PhD1.
1Services in Health Economics (SHE) BVBA, Schaerbeek, Belgium, 2argenx BV, Ghent, Belgium, 3argenx BV, Zwijnaarde, Belgium, 4Argenx, Boston, MA, USA.
1Services in Health Economics (SHE) BVBA, Schaerbeek, Belgium, 2argenx BV, Ghent, Belgium, 3argenx BV, Zwijnaarde, Belgium, 4Argenx, Boston, MA, USA.
OBJECTIVES: Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is a rare autoimmune disorder characterized by distal/proximal weakness and/or sensory deficits. This study seeks to estimate the minimal important difference (MID) of EQ-5D-5L utility values in patients with CIDP.
METHODS: ADHERE is the largest CIDP trial demonstrating the efficacy of efgartigimod. In the open-label stage, all patients (n=322) received efgartigimod for up to 12 weeks or until clinical improvement. Disability was assessed using the adjusted Inflammatory Neuropathy Cause and Treatment (aINCAT) score, ranging from 0 (no functional impairment) to 10 (inability to make any purposeful movement). Perceived improvement was captured by the Patient Global Impression of Change (PGIC) at the last assessment of stage A.
The EQ-5D-5L was recorded at baseline and at the last assessment of stage A. Different anchor-based methods were applied to estimate the MID. First, the MID was estimated as the mean utility change for patients reporting doing “a little better” on the PGIC. Using the aINCAT, three additional estimates were obtained: i) the mean utility change in patients with a 1-point decrease in aINCAT, ii) the regression coefficient of the change in utility versus change in aINCAT, iii) the optimal cut-off point of the receiver-operating characteristic (ROC) curve.
A distribution-based estimate was also derived, based on 0.5 times the baseline standard deviation.
RESULTS: The MID estimate based on PGIC was 0.11. Other methods yielded estimates of 0.14 (mean change for 1-point decrease on aINCAT), 0.10 (regression coefficient), 0.10 (ROC curve), and 0.14 (distribution-based estimate).
CONCLUSIONS: The MID estimate of 0.11 based on the PGIC aligns with prior research. The consistency of results supports an MID of 0.10-0.14 for CIDP patients, confirming efgartigimod benefits with a mean change of 0.13 in ADHERE and offering a useful reference point for the interpretation of utility changes in CIDP.
METHODS: ADHERE is the largest CIDP trial demonstrating the efficacy of efgartigimod. In the open-label stage, all patients (n=322) received efgartigimod for up to 12 weeks or until clinical improvement. Disability was assessed using the adjusted Inflammatory Neuropathy Cause and Treatment (aINCAT) score, ranging from 0 (no functional impairment) to 10 (inability to make any purposeful movement). Perceived improvement was captured by the Patient Global Impression of Change (PGIC) at the last assessment of stage A.
The EQ-5D-5L was recorded at baseline and at the last assessment of stage A. Different anchor-based methods were applied to estimate the MID. First, the MID was estimated as the mean utility change for patients reporting doing “a little better” on the PGIC. Using the aINCAT, three additional estimates were obtained: i) the mean utility change in patients with a 1-point decrease in aINCAT, ii) the regression coefficient of the change in utility versus change in aINCAT, iii) the optimal cut-off point of the receiver-operating characteristic (ROC) curve.
A distribution-based estimate was also derived, based on 0.5 times the baseline standard deviation.
RESULTS: The MID estimate based on PGIC was 0.11. Other methods yielded estimates of 0.14 (mean change for 1-point decrease on aINCAT), 0.10 (regression coefficient), 0.10 (ROC curve), and 0.14 (distribution-based estimate).
CONCLUSIONS: The MID estimate of 0.11 based on the PGIC aligns with prior research. The consistency of results supports an MID of 0.10-0.14 for CIDP patients, confirming efgartigimod benefits with a mean change of 0.13 in ADHERE and offering a useful reference point for the interpretation of utility changes in CIDP.
Conference/Value in Health Info
2025-11, ISPOR Europe 2025, Glasgow, Scotland
Value in Health, Volume 28, Issue S2
Code
SA31
Topic
Patient-Centered Research, Study Approaches
Disease
Neurological Disorders