Vigorimeter grip strength in CIDP: a responsive tool that rapidly measures the effect of IVIG the ICE study

Background and purpose In a recent trial in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), the ICE study, grip strength measurement captured significantly more improvement in patients receiving immune globulin (IGIV-C) intravenously than in those receiving placebo. Methods We conducted a systematic analysis to determine the sensitivity of grip strength as an indicator of meaningful clinical changes in CIDP. Results A randomized double-blind trial was undertaken in 117 CIDP patients who received IGIV-C or placebo every 3weeks for up to 24weeks. Grip strength and inflammatory neuropathy cause and treatment (INCAT) disability scores were assessed at each visit, and the responsiveness of each scale was compared. A minimum clinically important difference cut-off value for grip strength (>8kPa) and INCAT score (>1 point) was applied to assess the proportion of responders to IGIV-C versus placebo. This analysis showed that grip strength demonstrated significant improvement earlier (as early as day 16) than the INCAT disability scale in patients receiving IGIV-C compared with placebo. A significantly higher proportion of improvers were seen in the IGIV-C group (37.5%50.9%) than in the placebo group (21.1%25.9%) for grip strength at day 16, week 3, week 6 and the end of the first period. Also, grip strength showed within the first 6weeks in the placebo group significantly more patients with a clinically meaningful deterioration (>8kPa), compared with the INCAT (>1-point deterioration) findings. Conclusions Grip strength can be considered a sensitive tool for assessing clinically relevant changes in patients with CIDP. Its use in daily practice is suggested.