Item Reduction of the Boston Carpal Tunnel Questionnaire Using Decision Tree Modeling.

Objective: To produce an electronic decision tree version of the Boston Carpal Tunnel Questionnaire (DT-BCTQ) using the chi-squared automatic interaction detection (CHAID) algorithm to reduce questionnaire length of the Boston Carpal Tunnel Questionnaire (BCTQ) while minimizing the loss of measurement properties.

Design: Criterion standard study. All BCTQs completed between January 2012 and September 2016 by patients who were treated for carpal tunnel syndrome (CTS) were randomly divided into a development and a validation dataset at a 3-to-1 ratio. Optimization of the CHAID algorithm was performed in the development dataset to determine the most optimal DT-BCTQ.

Setting: Private hand clinic providing both surgical and nonsurgical (orthosis and exercise therapy) treatment for hand and wrist disorders.

Participants: Patients with CTS (N=4470) completed a total of 10,055 BCTQs.

Interventions: Not applicable.

Main Outcome Measures: The intraclass correlation coefficient (ICC) was calculated between the original BCTQ scores and the scores predicted by the DT-BCTQ in the validation dataset. Bland-Altman plots visualized the agreement between the BCTQ and the DT-BCTQ.

Results: The DT-BCTQ reduced the number of questions needed to ask a patient from 11 to a maximum of 3 for the symptom severity scale domain and from 8 to maximum of 3 for the functional status scale domain. The ICC between the original BCTQ and DT-BCTQ was 0.94. The mean difference between the BCTQ and DT-BCTQ was 0.05 on the 0-5 scale (95% confidence interval [CI], -0.48 to 0.57) for the symptom severity scale; 0.02 (95% CI, -0.45 to 0.49) for the functional status scale; and 0.04 (95% CI, -0.31 to 0.39) for the total BCTQ score.

Conclusion: By creating the DT-BCTQ, we diminished the number of questions needed to ask a patient from 18 to a maximum of 6 questions (3 for each subscore) when administering the BCTQ while maintaining an ICC of 0.94 with the original BCTQ.