Development, reliability, validity and sensitivity of the Sino-Nasal Outcome Test for Neurosurgery (SNOT-NC)

The transnasal endoscopic approach to lesions of the skull base has come into routine practice in recent years. Standardized questionnaires to assess the postoperative sequelae are missing. The authors present a custom-made questionnaire for the sino-nasal outcome test for neurosurgery (SNOT-NC) in accordance with the SNOT-22.

The SNOT-NC was developed with respect to the German version of the Sino-Nasal Outcome Test (SNOT-22) which is used for patients suffering from rhinosinusitis. It consists of 23 items covering "Nasal Discomfort", Sleep Problems/Reduced Productivity", "Ear and Head Discomfort", "Visual Impairment" and "olfactory impairment". The SNOT-NC was specifically adapted to patients undergoing transnasal operations of skull base lesions. The Short Form 36 health survey (SF-36), a nasal ad hoc questionnaire and the "Sniffin' Sticks" test were used for analyzing convergent and divergent validity. The psychometric and clinimetric analyses were performed using the data of 102 consecutive patients treated by transnasal operations for skull base lesions.

Factorial validity was secured by a confirmatory factor analysis. The internal consistency (Cronbach's Alpha) for the subscales ranged from .62 to .85, while it was .84 for the whole instrument. The Guttman's lower reliability limits range estimates corresponded closely to the Cronbach's Alpha coefficients obtained. Examination of convergent and divergent validity revealed substantial associations between the SNOT-NC and a wide range of related nasal symptoms (p < .05). Different aspects of sensitivity were analyzed statistically with Cohen's t statistic for change (pairwise t tests) exhibiting at least p < .05) underlining the sensitivity of the SNOT-NC.

The SNOT-NC appears to be a valid, reliable and sensitive measure for assessing the clinical outcome of patients undergoing transnasal endoscopic skull base surgery. The SNOT-NC proved to be a valuable tool to assess the nasal discomfort outcome of patients at follow-up examinations. Further analyses encompassing analyses for retest reliability are called for the future.