Tinnitus handicap inventory for evaluating treatment effects: which changes are clinically relevant?Otolaryngol Head Neck Surg. 2011 Aug; 145(2):282-7.OH
To determine the minimum change of the Tinnitus Handicap Inventory (THI) score that could be considered clinically relevant, the authors compared the absolute change of the THI with the Clinical Global Impression–Improvement (CGI-I) score.
International studies register with standardized data collection.
Tinnitus Research Initiative (TRI).
SUBJECTS AND METHODS
Two hundred ten patients of the TRI database were eligible for this study. In the first analysis, the THI score change and CGI-I ratings were compared with equipercentile linking. In a second analysis, the authors categorized the CGI-I into the 4 groups much better or better, minimally better, no change, and worse and calculated the corresponding differences of the THI score and the effect sizes. An effect size separating the minimally better and the no-change groups was chosen, and the referring THI mean score difference was calculated.
According to the linking method, a CGI-I value of 3 (minimally better) corresponded to a THI score reduction of 6 to 16, whereas the CGI-I value of 4 (no change) corresponded to the range between improvement by 5 points and worsening by 4 points. For separating the no-change and minimally better groups, an effect size d = 0.5 was determined, resulting in a minimal clinically relevant difference of ΔTHI = 7.
Two different methods yielded comparable results in identifying a reduction in the THI score of 6 and 7 points, respectively, as the minimal clinically relevant change. This study provides a first orientation for sample size calculations and for planning the design of future studies.