Quantifying Treatment-Related Fluctuations in CIDP: Results of the GRIPPER Study

Abstract

Objective: The objective of this study was to explore the extent of IV immunoglobulin (IVIG) treatment-related fluctuations (TRFs) by using home collection of daily grip strength in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and to use that information to develop evidence-based treatment optimization strategies.

Methods: This prospective observational study included 25 patients with well-defined CIDP. Participants recorded grip strength daily for 6 months. Disability and gait metrics were collected weekly. Serum immunoglobulin G levels were obtained at peak, trough, and midcycle IVIG intervals. Day-to-day grip strength changes <10% were considered random. To identify patients with TRFs, 3-day averaged grip strength was calculated on each consecutive day after an IVIG infusion. TRFs were defined as ≥10% 3-day averaged grip strength difference compared to the pre-IVIG baseline.

Results: Participants successfully recorded grip strength on all but 9% of recordable days. Twelve patients (48%) were classified as low/no fluctuaters and 13 (52%) as frequent fluctuaters. In the frequent fluctuating group, grip strength improved over 1 week and thereafter was relatively stable until the third week after infusion. Grip strength was significantly correlated with measures of disability.

Conclusions: Grip strength collection by patients at home is reliable, valid, and feasible. A change in grip strength by ≥10% is a useful, practical, and evidence-based approach that may be used to identify clinically meaningful TRFs. From these data, we propose a treatment optimization strategy for patients with CIDP on chronic IVIG that may be applied to routine clinic care during both face-to-face and virtual video or telephone patient encounters.

Trial registration information: ClinicalTrials.gov Identifier: NCT02414490.

© 2021 American Academy of Neurology.

Figures

Figure 1. Correlation Between Grip Strength Collected by Patients and Nurses in Dominant and Nondominant Hands

Figure 2. Dominant and Nondominant Hand TRFs in 25 Patients

Treatment-related fluctuation (TRF) deterioration (white), TRF improvement (black), or no TRFs (gray) in patients receiving IV immunoglobulin (IVIG). D = dominant hand; N = nondominant hand. *Patients classified as frequent fluctuaters.

Figure 3. Percent Change in 3-Day Averaged Dominant and Nondominant (Combined) Hand Grip Strength

Grip strength across all patients and all cycles in participants with (A) frequent treatment-related fluctuations (TRFs) and (B) low or no TRFs.

Figure 4. Proposed Approach to IVIG Optimization for Patients With CIDP on Long-Term IVIG Therapy

CIDP = chronic inflammatory demyelinating polyradiculoneuropathy; GS = grip strength; IVIG = IV immunoglobulin; TRF = treatment-related fluctuation.