Establishing the minimal clinically important difference for the Questionnaire of Olfactory Disorders

Jose L. Mattos, Rodney J. Schlosser, Jess C. Mace, Timothy L. Smith, Zachary M. Soler

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Background: Olfactory-specific quality of life (QOL) can be measured using the Questionnaire of Olfactory Disorders Negative Statements (QOD-NS). Changes in the QOD-NS after treatment can be difficult to interpret since there is no standardized definition of clinically meaningful improvement. Methods: Patients with chronic rhinosinusitis (CRS) completed the QOD-NS. Four distribution-based methods were used to calculate the minimal clinically important difference (MCID): (1) one-half standard deviation (SD); (2) standard error of the mean (SEM); (3) Cohen's effect size (d) of the smallest unit of change; and (4) minimal detectable change (MDC). We also averaged all 4 of the scores together. Finally, the likelihood of achieving a MCID after sinus surgery using these methods, as well as average QOD-NS scores, was stratified by normal vs abnormal baseline QOD-NS scores. Results: Outcomes were examined on 128 patients. The mean ± SD improvement in QOD-NS score after surgery was 4.3 ± 11.0 for the entire cohort and 9.6 ± 12.9 for those with abnormal baseline scores (p < 0.001). The MCID values using the different techniques were: (1) SD = 6.5; (2) SEM = 3.1; (3) d = 2.6; and (4) MDC = 8.6. The MCID score was 5.2 on average. For the total cohort analysis, the likelihood of reporting a MCID ranged from 26% to 51%, and 49% to 70% for patients reporting preoperative abnormal olfaction. Conclusion: Distribution-based MCID values of the QOD-NS range between 2.6 and 8.6 points, with an average of 5.2. When stratified by preoperative QOD-NS scores the majority of patients reporting abnormal preoperative QOD-NS scores achieved a MCID.

Original languageEnglish (US)
Pages (from-to)1041-1046
Number of pages6
JournalInternational Forum of Allergy and Rhinology
Issue number9
StatePublished - Sep 2018


  • minimal clinically important difference
  • olfaction
  • questionnaire of olfactory disorders
  • sinusitis

ASJC Scopus subject areas

  • Immunology and Allergy
  • Otorhinolaryngology


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