Psychometric Validation of the Overall Symptom Severity Score for Chronic Rhinosinusitis.

Abstract

Overall symptom severity (OSS) is a global metric of chronic rhinosinusitis (CRS) symptom severity. We sought to establish psychometric validity for the OSS, which has not been previously demonstrated in the literature. Prospective, observational. Academic medical center. Adult patients with CRS (N = 647) recruited and completed an OSS score (measured using a visual analog scale [VAS]), 22-item Sinonasal Outcome Test (SNOT-22), and 5-level EuroQol (EQ-5D) questionnaires. A subset of participants completed these questionnaires at a second time point to establish test-retest reliability (N = 65) and responsiveness to change (N = 225). Psychometric validation was performed by establishing criterion validity, test-retest reliability, and responsiveness in these CRS patients. The OSS score was significantly correlated with SNOT-22 (r = 0.73, 95% CI: 0.69-0.76, P < .001) and EQ-5D VAS scores (r = -0.39, 95% CI: -0.46 to -0.33, P < .001) at enrollment, demonstrating criterion validity. For the subset of participants who completed the OSS at a second time point ranging between 31 and 143 days later, the change in OSS was correlated with changes in SNOT-22 score (r = 0.72, 95% CI: 0.65-0.78, P < .001), and EQ-5D VAS (r = -0.30, 95% CI: -0.42 to -0.18, P < .001). The OSS score also demonstrated excellent test-retest reliability (r = 0.92, 95% CI: 0.87-0.95, P < .001). Using a distribution-based and four different anchor-based calculations, the minimal clinically important difference (MCID) for improvement and worsening for the OSS score was determined as ≥1.6 (or >1.5). The OSS score is a psychometrically valid measure of CRS symptom severity, with excellent criterion validity, test-retest reliability, and responsiveness. The MCIDs for improvement and worsening are proposed to be ≥1.6 (or >1.5).