Self-administered outcome instrument in carpal tunnel syndrome. Reliability, validity and responsiveness evaluated in 102 patients

We evaluated a Swedish version of a self-administered disease-specific outcome questionnaire for carpal tunnel syndrome regarding reliability, validity and responsiveness to clinical change. It consists of multi-item scales assessing symptom severity, function, patient satisfaction and quality of life. It was given to 102 patients before and 3 months after carpal tunnel release. Test-retest reliability, studied in a subsample of 22 patients on two occasions with a 1-3-week interval, showed good agreement between the scores. Internal consistency of the scales was high (Cronbach alpha 0.80-0.95). Validity of the scales was evaluated using the SF-36 general health questionnaire in a subgroup of 48 patients as well as items concerning patient satisfaction, showing the expected relationships between these measures. Responsiveness of the scales to clinical change, estimated by the effect size and standardized response mean, was large (0.94-1.7). We conclude that this questionnaire can provide a standardized measure of symptom severity and functional status, as well as patient satisfaction and quality of life in the carpal tunnel syndrome