Psychometric evaluation of a new sensory scale in immune-mediated polyneuropathies

Objective: To perform a psychometric evaluation of the inflammatory neuropathy cause and treatment (INCAT) sensory sumscore (ISS) in sensory–motor immune-mediated polyneuropathies. This new sensory scale was evaluated to strive for uniformity in assessing sensory deficit in these disorders. Methods: The ISS comprises vibration and pinprick sense plus a two-point discrimination value and ranges from 0 (normal sensation) to 20 (maximum sensory deficit). Before its clinical use, a panel of expert neurologists concluded that the ISS has face and content validity. The construct validity of the ISS was investigated by correlation and regression studies with additional scales (Nine-Hole Peg Test, 10-Meter Walking Test, a disability sumscore). All scales were applied in 113 patients with a stable neurologic condition (83 patients who experienced Guillain–Barré syndrome [GBS] in the past, 22 with chronic inflammatory demyelinating polyneuropathy [CIDP], 8 patients with a monoclonal gammopathy associated polyneuropathy), and 10 patients with recently diagnosed GBS or CIDP with changing clinical conditions. Reliability of the ISS was evaluated in the stable patients. Its responsiveness was investigated in the patients examined longitudinally. Results: A moderate to good validity was obtained for the ISS (stable group: r = 0.38 to 0.56, p ≤ 0.006; longitudinal group: R = 0.60 to 0.82, p ≤ 0.007, except for the association with the 10-Meter Walking Test [p = 0.08]). Acceptable internal consistency, and inter- and intraobserver reliability were demonstrated for the ISS (α = 0.68 to 0.87; R = 0.85 to 0.89, p < 0.0001). Standardized response mean scores for the ISS were high (≥0.8), indicating good responsiveness. Conclusions: All psychometric requirements are provided for the the inflammatory neuropathy cause and treatment sensory sumscore. The use of this scale is therefore suggested for bedside evaluation of sensory deficit in the individual patient with a sensory–motor immune-mediated polyneuropathy as well as in clinical trials.