Dissociation between odor identification and threshold in primary Sjögren's syndrome

This study aimed to compare olfactory threshold and odor identification performance between patients with pSS and healthy controls, and to evaluate the discriminatory capacity of olfactory testing in this population.

In this prospective, single-center case-control study, 46 patients with pSS and 46 age- and sex-distribution-matched healthy controls were enrolled. Odor identification was assessed using the 12-item Rapid Sniffin' Sticks test, and olfactory threshold was evaluated using a modified CCCRC n-butanol protocol. Associations between olfactory measures and disease-related variables were analyzed. Multivariable linear and logistic regression models were constructed, and receiver operating characteristic (ROC) analysis was performed to assess discriminatory performance.

Odor identification scores were significantly lower in patients with pSS compared with controls (p < 0.001), whereas olfactory threshold scores did not differ between groups. Within the pSS group, no significant associations were observed between olfactory measures and ESSPRI, disease duration, ESR, or CRP; however, because patients with organ involvement were excluded, these findings should not be interpreted as evidence against activity-dependent olfactory dysfunction. In multivariable analysis, pSS status remained independently associated with lower identification scores (p < 0.001). ROC analysis demonstrated good discriminatory performance for odor identification (AUC = 0.828), with an optimal cutoff of ≤ 8 (sensitivity 0.674; specificity 0.891). Adding threshold to the model resulted in minimal improvement (AUC = 0.837).

Patients with pSS exhibited impaired odor identification, whereas no statistically significant difference was observed in olfactory threshold scores. Odor identification testing may serve as an adjunctive clinical tool; however, its diagnostic role requires external validation. The study design does not permit firm conclusions regarding the relationship between olfactory dysfunction and disease activity.

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