Small, moderate, and large changes, and the minimum clinically important difference in the University of California, San Diego Shortness of Breath Questionnaire.

AbstractMinimum clinically important change of 5 points in the University of California, San Diego Shortness of Breath Questionnaire (SOBQ) is established, but cutoff values between a small, a moderate, and a large change are still unknown. We used the data set of National Emphysema Treatment Trial consisting of severe and very severe chronic obstructive pulmonary disease patients, whose mean age was 64 years. Changes from baseline to post-surgical 6-month follow-up were evaluated. The St. George's Respiratory Questionnaire was used as anchor: |∆SGRQ| < 4, meaningless change; 4 ≤ |∆SGRQ| < 8, small change; 8 ≤ |∆SGRQ| < 13, moderate change; 13 ≤ |∆SGRQ|, large change. We decided the final cutoff values for the SOBQ as medians of the three anchor methods. We also decided the range of cutoff values as the range of three values. In a cohort of surgically treated patients (N = 484), we propose value of 5 (range 5–6), 11 (range 9–15), and 16 (range 14–20) for the cutoff values between a meaningless and a small...