Secondary Validation of the Parosmia Olfactory Dysfunction Outcomes Rating (DisODOR): Analysis of a Randomized Clinical Trial

Background: The DisODOR is the only validated disease-specific patient-reported outcome measure (PROM) for patients with parosmia. No published data supports the use of the instrument to monitor response after an intervention. The objective of this study was to secondarily analyze a randomized clinical trial (RCT) to assess the instrument’s responsiveness to change. Methods: A double-blinded, placebo-controlled RCT with parosmic patients undergoing stellate ganglion block was conducted. The DisODOR was completed at baseline and 3 months, and the Clinical Global Impression – Improvement (CGI-I) score, which is a 7-point Likert scale assessing response of smell distortion to treatment, was given at 3 months. The primary outcome measure of this study was the responsiveness to change of the DisODOR. The secondary outcome measures were the instrument’s internal consistency measured via Cronbach’s alpha and test-retest reliability calculated by Pearson correlation. Results: A total of 46 participants with a mean (SD) age of 44 (12) years were analyzed. At 3-month follow-up, there was a mean (SD) change in DisODOR score of −47 (15) for participants reporting much improved (n = 5), −35 (17) for moderately improved (n = 9), −29 (20) for slightly improved (n = 3), and −4 (13) for no change (n = 25) (eta squared [η²] = .63). Four patients reported worsening of parosmia with a mean (SD) change in DisODOR score of 11 (16). The internal consistency was excellent at .91 and test-retest reliability strong at .85 (95% CI = 0.68-0.93). Conclusion: This study provided RCT-level evidence for the DisODOR’s strong responsiveness to change, internal consistency, and test-retest reliability. The instrument is an ideal PROM for both clinical use and research, particularly given the difficulty in otherwise quantifying parosmia severity.