Minimal Clinically Important Differences in Hand Pain Intensity (Numerical Pain Rate Scale) and Related-Function (Boston Carpal Tunnel Questionnaire) in Women With Carpal Tunnel Syndrome

Abstract

Objective: To calculate the minimal clinically important differences (MCIDs) for hand pain intensity and the Boston Carpal Tunnel Questionnaire (BCTQ) in a sample of women with carpal tunnel syndrome (CTS).

Design: Secondary analysis of a randomized controlled trial.

Setting: A Hospital Rehabilitation Unit.

Participants: One hundred twenty women with clinical and electromyographic diagnosis of CTS who were randomly assigned into 2 groups (N=120).

Interventions: One group received 3 sessions of manual physical therapy (n=60) and the other group received surgery (n=60).

Main outcome measures: Mean and the worst pain intensity (numerical pain rate scale, 0-10 points) and functional status and symptoms' severity subscales of the BCTQ questionnaire were assessed before and 1 month after treatment. The Global Rating of Change (GROC) was used as the anchor variable for determining the MCID.

Results: A change of 1.5 and 2.5 points in mean and the worst pain intensity represents the MCID for Numerical Pain Rating Scale, whereas a change of 0.23 and 0.64 points in functional status and symptoms' severity represents the MCID for each subscale of the BCTQ. All variables showed acceptable discrimination between patients classified as "improved" and those classified as "stable/not improved" (area under the curve≥0.72). Mean pain intensity (Youden index, 0.53; sensitivity: 73.3%; specificity: 80%) and symptoms' severity (Youden index, 0.69; sensitivity: 90%; specificity: 77.8%) showed the best discriminative ability expressed as a percentage of prediction. Participants classified as "improved" had significantly greater improvements in pain intensity, functional status, and symptoms' severity compared with those classified as "stable/not improved".

Conclusion: A change of 1.5 and 2.5 points in mean and the worst pain and a change of 0.23 and 0.64 points in functional status and symptoms' severity represents the MCID for pain intensity and BCTQ in women with CTS 1 month after treatment.

Trial registration: ClinicalTrials.gov NCT01789645.

Keywords: Carpal tunnel syndrome; Function; Minimal detectable change; Pain; Rehabilitation.