Psychometric validity of the 22‐item Sinonasal Outcome Test

We set out to determine the psychometric validation of a disease-specific health related quality of life instrument for use in chronic rhinosinusitis, the 22 item Sinonasal Outcome Test (SNOT-22), a modification of a pre-existing instrument, the SNOT-20. DESIGN, SETTING AND PARTICIPANTS: The National Comparative Audit of Surgery for Nasal Polyposis and Chronic Rhinosinusitis was a prospective cohort study collecting data on 3128 adult patients undergoing sinonasal surgery in 87 NHS hospitals in England and Wales. Data were collected preoperatively and at 3 months after surgery, and analysed to determine validity of the SNOT-22. Test-retest reliability was assessed in a separate cohort of patients in a single centre. MAIN OUTCOME MEASURES: The SNOT-22, a derivative of the SNOT-20 was the main outcome measure. Patients were also asked to report whether they felt better, the same or worse following surgery. To evaluate the SNOT-22, the internal consistency, responsiveness, known group differences and validity were analysed.

Preoperative SNOT-22 scores were completed by 2803 patients. 3-month postoperative SNOT-22 scores were available for 2284 patients of all patients who completed a preoperative form (81.5% response rate). The Cronbach's alpha scores for the SNOT-22 were 0.91 indicating high internal consistency. The test-retest reliability coefficient was 0.93, indicating high reliability of repeated measures. The SNOT-22 was able to discriminate between patients known to suffer with chronic rhinosinusitis and a group of healthy controls (P