Impairment, disability, or handicap in peripheral neuropathy: analysis of the use of outcome measures in clinical trials in patients with peripheral neuropathies.

Outcome measures can be classified into measures of impairment, disability, and handicap. To investigate the biological effect of treatment, measures of impairment are appropriate. Studies investigating whether patients benefit from treatment in terms of improvement of functional health, however, require disability or handicap measures. In a review of the medical literature between 1978 and 1993, 73 controlled intervention studies in patients with peripheral neuropathies were found. Disability or handicap measures were used in two of 54 studies in patients with diabetic neuropathy, in two of six studies in patients with chronic inflammatory demyelinating polyneuropathy, in none of five studies in a mixed group of patients, and in all eight studies in patients with Guillain-Barré syndrome. The limited use of disability and handicap measures in patients with diabetic and mixed neuropathies can be explained by the experimental nature of most studies. In four of six studies, however, in patients with chronic inflammatory demyelinating polyneuropathy or neuropathy associated with monoclonal gammopathy that were designed to assess effectiveness of treatment, the choice of outcome measures was not appropriate. It is concluded that in the design of intervention studies in patients with peripheral neuropathy more attention should be paid to a proper choice of suitable outcome measures to assess the effectiveness of treatment.