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

Objective: The objective of this study was to explore the extent of IVIG treatment related fluctuations (TRF) by using home collection of daily grip strength in patients with 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 IgG levels were obtained at peak, trough and mid-cycle IVIG intervals. Day-to-day grip strength changes 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 one week, and thereafter was relatively stable until the 3rd week post 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. Based upon this 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.