The significance of response shift in sinus surgery outcomes.

BACKGROUND: Functional endoscopic sinus surgery (FESS) aims to improve quality-of-life (QOL). Perception of QOL can change according to one's current medical or emotional state. This is known as response shift. It can be measured by the "then-test," which asks patients to report pretreatment symptoms after receiving treatment. Patients often do not understand their disease burden until their symptoms are improved. This study aims to assess the significance of response shift in FESS outcomes.
METHODS: This was a prospective cohort study that included chronic rhinosinusitis patients from 2010 to 2012 who completed a preoperative 20-item Sino-Nasal Outcome Test (SNOT-20). Two SNOT-20 forms were mailed approximately 6 months after surgery. Patients completed 1 SNOT-20 according to their preoperative symptoms in light of their current state of health ("then-test") and the other based on postoperative symptoms. The preoperative and postoperative SNOT-20 difference represented the treatment effect and the preoperative SNOT-20 and then-test difference represented the response shift.
RESULTS: Thirty-two completed responses were obtained. Using a 0 to 5 scale, mean treatment effect was -0.96 (p < 0.01), which signifies a QOL improvement. Mean response shift was +0.42 (p = 0.01). This positive value signifies that patients felt they were worse off preoperatively, likely due to a positive change in health status. The actual treatment effect is the sum of the measured treatment effect and response shift, which was -1.38.
CONCLUSION: Response shift exists and can be quantified. The actual treatment effect was more profound when response shift was included. Therefore, future studies should account for this often unmeasured, potential change in QOL.