Interpreting clinically significant changes in patient‐reported outcomes

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Abstract
BACKGROUND. The goal of this study was to determine what magnitude of change in a patient‐reported outcome score is clinically meaningful, so a clinicians' guide may be provided for estimating the minimal important difference (MID) when empiric estimates are not available. METHODS. Consecutive laryngeal cancer patients (n = 98) rated their quality of life (QOL) relative to other patients. These comparisons were contrasted with arithmetic differences in scores on the Functional Assessment of Cancer Therapy‐Head and Neck (FACT‐H&N) scale, Functional Assessment of Cancer Therapy‐General (FACT‐G) scale, 2 utility measures (the time tradeoff [TTO] and Daily Active Time Exchange [DATE]), and performance status (Karnofsky) scores. RESULTS. The FACT‐H&N score needed to differ by 4% for average patients to rate themselves as “a little bit better” relative to other patients (95% CI, 1%–8%) and by 9% to rate themselves as “a little bit worse” relative to others (95% CI, 4%–13%). The corresponding values for other measures were FACT‐G 4% (1%–7%) and 8% (95% CI, 5%–11%); TTO 5% (95% CI, 0%–11%) and 6% (95% CI, 0%–10%); DATE 5% (95%CI, 2%–9%) and 14% (95% CI, 0%–5%); Karnofsky 4% (95% CI, 1%–6%) and 10% (95% CI, 7%–13%). In each case, the minimal important difference (MID) was about 5% to 10% of the instrument range. CONCLUSIONS. One rule of thumb for interpreting a difference in QOL scores is a benchmark of about 10% of the instrument range. Patients appear to be more sensitive to favorable differences, so an improvement of 5% may be meaningful. This simple benchmark may be useful as a rough guide to meaningful change. Cancer 2007. © 2007 American Cancer Society.