Assessing grip strength in healthy individuals and patients with immune-mediated polyneuropathies

Grip strength reference values for a portable dynamometer, the hand-held Vigorimeter, were calculated, and its validity, reliability, and responsiveness were examined in patients with immune-mediated polyneuropathies. We studied 530 healthy controls (age 5-93 years), 113 patients with stable polyneuropathy (83 with Guillain-Barré syndrome [GBS], 22 with chronic inflammatory demyelinating polyneuropathy [CIDP], and 8 with a gammopathy-associated polyneuropathy), and 20 patients with GBS or CIDP and changing clinical conditions (longitudinal group). An arm-disability scale was also assessed. Grip-strength reference values were calculated depending primarily on age and gender. Significant association was obtained between the Vigorimeter and the arm scale (in stable group, Spearman rank: r = -0.52 to -0.62; P </= 0.0005; in longitudinal group, linear regressions: r = 0.62-0.64, P < 0.0001). Good interobserver and intra-observer agreements (analysis of variance, r = 0.95-0.97) and high responsiveness (standardized response mean scores > or = 0.8) were demonstrated for the Vigorimeter. These results emphasize the clinical usefulness of the Vigorimeter, particularly in patients with immune-mediated polyneuropathies.