Minimal important differences and self‐identifying treatment response in chronic inflammatory demyelinating polyneuropathy

Abstract

Introduction/Aim: The use of outcome measures is recommended for chronic inflammatory demyelinating polyneuropathy (CIDP). Implications of minimal important differences (MID) to ascertain responder status are unknown. The reliability of patient-reported treatment-response in relation to clinically relevant change is also unknown.Methods: We retrospectively studied 72 subjects with "definite" or "probable" CIDP evaluated at pre-specified time-intervals pre-and post-treatment. We derived MID and the minimum detectable change with 95% confidence intervals (MDC 95 ) for four scales. Scale sensitivities were determined with applicable MID-defined cutoffs (aMIDc), to detect subjects with self-identifying treatment response through a single question.Results: The use of MID was not valid for the Medical Research Council Sum Score, as MDC 95 > MID. The aMIDc for the Overall Neuropathy Limitation Score (ONLS) was 1 (sensitivity: 84.7%). The aMIDc for the centile Inflammatory Rasch-built Overall Disability Scale (cI-RODS) was 8 (sensitivity: 62.3%). The aMIDc for grip strength was 4 kg (sensitivity: 79.1%). MID-defined amelioration of any one scale among ONLS, cI-RODS, or grip strength, significantly improved sensitivity to detect treatment-responders compared with the ONLS alone

Predicting long‐term trends in inflammatory neuropathy outcome measures using latent class modelling

“…The former approach is commonly applied in clinical practice and has been used in comparable cohort studies 10,16 . Frequent deviations in the i‐RODS above 4 logit points observed in our clinically stable cohort questions the reliability of this measurement in the individual, or suggests that the true MCID for the i‐RODS is higher than this value which is supported by recent patient‐reported treatment response analysis proposing MCID for the i‐RODS at 8 points 20 …”

“…10,16 Frequent deviations in the i-RODS above 4 logit points observed in our clinically stable cohort questions the reliability of this measurement in the individual, or suggests that the true MCID for the i-RODS is higher than this value which is supported by recent patient-reported treatment response analysis proposing MCID for the i-RODS at 8 points. 20 We found grip strength to fluctuate less than i-RODS and MRC-SS. However, studies of daily grip strength measurement have indicated that averaging consecutive readings over 3 days is required to smooth out random variation and reliably detect change.…”

Assessing deterioration using impairment and functional outcome measures in chronic inflammatory demyelinating polyneuropathy: A post‐hoc analysis of the immunoglobulin overtreatment in CIDP trial

“…This implies that variability exceeding MCIDs in stable patients is also common in clinical care. Another study of CIDP patients investigated the minimum detectable change (MDC), 27 which is conceptually similar to the limits of variability used in our study, as both reflect the threshold of changes beyond that what can be observed in stable patients. The MDC of I‐RODS was smaller than limits of variability in our data 27 .…”

“…Another study of CIDP patients investigated the minimum detectable change (MDC), 27 which is conceptually similar to the limits of variability used in our study, as both reflect the threshold of changes beyond that what can be observed in stable patients. The MDC of I‐RODS was smaller than limits of variability in our data 27 . Also, contrary to our results, the distribution‐based MCID value of grip strength and the I‐RODS exceeded the MDC, 27 indicating that clinically meaningful changes can be distinguished from random variability.…”

Measuring treatment response to chronic inflammatory demyelinating polyneuropathy in clinical practice: More than just asking

“…In this issue of Muscle and Nerve, Rajabally and colleagues report the results of a retrospective study that aims to better understand how response to CIDP treatment can be defined in clinical practice. 12 Outcomes that have been historically collected in clinical trials including strength impairment (Medical Research Council [MRC] sum score, grip strength using a handheld dynamometer) and disability (overall neuropathy limitations scale [ONLS] disability score, I-RODS disability score) were obtained pre-and post treatment. Additionally, after treatment all participants were asked a standard question to capture the patient perception of treatment response: "Do you feel you have been improved by the treatment for your CIDP?".…”