ObjectiveThe purpose was to evaluate the relationship between peripheral eosinophilia, Japan Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis (JESREC) score, and olfactory dysfunction in chronic rhinosinusitis (CRS) patients and to explore the accuracy and specific cut points of the JESREC score in predicting olfactory dysfunction.MethodsIn this cross-sectional, retrospective study, olfactory function was assessed by the Sniffin’ Sticks 12-item test and multivariate logistic regression analyses were carried out. Receiver operating characteristic curves were plotted to derive accuracy and cutoff values for the JESREC scores of the olfactory dysfunction criterion.ResultsA total of 354 patients [mean (SD) age, 50.0 (14.9) years; 41.8% women] were included in the final analysis. The prevalence of olfactory dysfunction was 46.3%. Individuals who had olfactory dysfunction were more likely to be male (64.6% vs. 52.6%), have eosinophilic chronic rhinosinusitis (ECRS) (39.0% vs. 7.9%), have a longer course of CRS (2.3 years vs. 1.5 years), have higher JESREC scores (8.5 vs. 4.5), and have higher proportions of nasal polyps (78.7% vs. 18.9%) and peripheral eosinophilia (3.3% vs. 1.4%). In logistic analysis, the percentage of eosinophils (1.25, 1.13–1.37), JESREC score (1.31, 1.22–1.40), bilateral lesion (2.06, 1.25–3.41), nasal polyps (15.83, 9.23–27.16), CT shadow (2.73, 1.69–4.43), and ECRS (6.86, 3.68–12.80) were associated with olfactory dysfunction in CRS patients after controlling for covariates, while peripheral neutrophils were not significant. In addition, the area under the curve was 0.778 and the cutoff value for JESREC score for olfactory dysfunction was defined as 5.5.ConclusionsPeripheral eosinophilia and high JESREC scores were significantly associated with the risk of olfactory dysfunction in CRS patients, and special attention should be paid to patients with a JESREC score ≥6.