The minimal clinically important difference of the Carpal Tunnel Syndrome Symptom Severity Scale.

PURPOSE: To identify the change score in the Symptom Severity Scale (SSS) of the Carpal Tunnel Syndrome (CTS) Questionnaire that is associated with an important change in clinical status.

METHODS: Twenty-eight patients with CTS treated with a carpal tunnel steroid injection completed the Brigham and Women's Hospital CTS Questionnaire before steroid injections and at the 3-week follow-up visit. Satisfaction was determined by postcare review of the clinical management. To calculate the minimal clinically important difference, receiver operating characteristic curves were created. The area under the curve was calculated to determine and compare the responsiveness of the entire SSS and the pain and sensory questions in isolation.

RESULTS: The SSS of the CTS Questionnaire, including its pain and sensory domain, can show a meaningful clinical improvement after carpal tunnel injection. The SSS, its sensory domain, and its pain domain were statistically better than chance. All 3 measures showed predictive ability; however, the total SSS was the most sensitive in detecting a change. The minimal clinically important difference in the score of the SSS after carpal tunnel steroid injection was found to be 1.04.

CONCLUSIONS: The SSS can be used to distinguish a clinically important change after carpal tunnel injection. A decrease of 1.04 or more in the SSS score may indicate a clinically important change in a patient's state of health.

TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic, Level I.