Psychometric evaluation of the sinonasal outcome test-16 and activity impairment assessment in acute bacterial sinusitis

Objective. To validate the Sinonasal Outcome Test-16 and Activity Impairment Assessment in patients with acute bacterial sinusitis. Study Design. Data were used from a phase III clinical trial designed to evaluate the efficacy and safety of moxifloxacin 400 mg once daily for 5 consecutive days in the treatment of acute bacterial sinusitis. The psychometric properties and factor structure of the 2 measures were assessed. Setting. Participants were given the measures to selfcomplete using either a telephone voice response system or a paper-and-pencil format. Subjects and Methods. Three hundred seventy-four patients with acute bacterial sinusitis were used in the analysis. Patients received either a placebo or 400 mg moxifloxacin once daily. Patients were then reviewed at test of cure and follow-up. All analyses were conducted on a combined sample of placebo and active treatment patients. Results. The Sinonasal Outcome Test-16 was associated with minimal missing data at baseline but a higher proportion by test of cure. There was no evidence of floor or ceiling effects and no significant skew. The Activity Impairment Assessment also had low missing data at baseline and no obvious floor or ceiling effects, but the data were not normally distributed. Both measures had good internal consistency. Convergent and divergent validity as well as sensitivity and the minimally important difference are also reported. Conclusion. The measures both have good psychometric properties and are suitable for use with patients with acute bacterial sinusitis. Both instruments are sensitive. The minimal important difference estimates for the Sinonasal Outcome Test-16 are quite high but are similar to estimates reported previously.