Exploring possibilities for shortening the 22-item Sino-Nasal Outcome Test (SNOT-22) using item response theory.

ABSTRACT

BACKGROUND: Even with a high-quality instrument, such as the 22-item Sino-Nasal Outcome Test (SNOT-22), patients can be overwhelmed by repeated completion of questionnaires, leading to nonadherence and reduced data quality. The aim of this study was to evaluate whether the SNOT-22 could be made more concise without losing the valuable information that it provides. METHODS: A modern psychometric approach, item response theory (IRT), was used on a sample of 800 patients with chronic rhinosinusitis (CRS). The SNOT-22 was refined based on (1) the item information criteria, retaining only items with above-average information; and (2) the total test information, retaining only the most discriminating items to cover at least 30% of the information within each subdomain. The preliminary validity and reliability of these refined scales were assessed using Cronbach's alpha and Pearson's correlation. RESULTS: Using an IRT approach, we find that it may be possible to shorten the SNOT-22 to an 11-item and six-item version based on psychometric properties. Item information functions of the shortened 11-item and six-item scales demonstrate that both versions accurately covered the CRS symptom-severity continuum. Preliminary reliability and validity analysis showed that both refined scales had good to excellent reliability (Cronbach's alpha ≥ 0.80) and were highly associated with the original full-length scale (r ≥ 0.90). CONCLUSION: IRT provides data-driven opportunities for the continuous development and refinement of the SNOT-22. While patient and provider input must be accounted for too, our results show that future revisions of the SNOT-22 could include significantly fewer items.