Clinimetric evaluation of a new overall disability scale in immune mediated polyneuropathies
- I S J Merkies1,
- P I M Schmitz2,
- F G A van der Meché1,
- J P A Samijn1,
- P A van Doorn1,
- for the Inflammatory Neuropathy Cause and Treatment (INCAT) group
- 1Department of Neurology, University Hospital Rotterdam/Erasmus University, dr Molewaterplein, Rotterdam, Netherlands
- 2Department of Statistics, Daniel den Hoed Cancer Centre, University Hospital Rotterdam/Erasmus University
- Correspondence to: Dr I S J Merkies, Department of Neurology, St Elisabeth Hospitaal, Breedestraat 193 (O), Willemstad, Curaçao, Netherlands Antilles;
- Received 8 December 2000
- Accepted 24 January 2002
- Revised 23 October 2001
Objectives: To determine the validity, reliability, and responsiveness of a new overall disability sum score in immune mediated polyneuropathies.
Methods: Three impairment measures (MRC sum score, sensory sum score, grip strength (Vigorimeter)) and three disability scales (an overall disability sum score (ODSS), Hughes' functional scale (f score), Rankin scale) were assessed in a cross sectional group of 113 clinically stable patients (83 with Guillain–Barré syndrome, 22 with chronic inflammatory demyelinating polyneuropathy (CIDP), eight with a gammopathy related polyneuropathy). The ODSS was also used serially in 20 patients with recently diagnosed Guillain–Barré syndrome (n = 7) or CIDP (n = 13) and changing clinical conditions. Multiple regression studies were performed to compare the impact of impairment disturbances (independent variables) on the various disability scales (dependent variable).
Results: Moderate to good construct validity (stable group: Spearman's rank test (absolute values), r = 0.41–0.79; longitudinal group: multiple correlation coefficient, R = 0.69–0.89; p < 0.006 for all associations) and reliability (intraclass correlation coefficient, R = 0.90–0.95; p < 0.0001) were demonstrated for the ODSS. Its SRM values were high (> 0.8), indicating good responsiveness. Impairment measures accounted for a higher variance proportion of the ODSS compared with the f score and Rankin (R = 0.64 v 0.56 and 0.45, respectively).
Conclusions: All clinimetric requirements were met by the overall (arm and leg) disability sum score in immune mediated polyneuropathies. Its use is therefore suggested in evaluating immune mediated polyneuropathies.
- CIDP, chronic demyelinating polyneuropathy
- GBS, Guillain—Barré syndrome
- INCAT, inflammatory neuropathy cause and treatment group
- MGUSP, monoclonal gammopathy of undetermined significance
- MRC, Medical Research Council
- ODSS, overall disability sum score
- SRM, standardised response mean