Mucous Cytokine Levels in Chronic Rhinosinusitis-Associated Olfactory Loss

Olfactory loss is a frequent symptom of patients with chronic rhinosinusitis (CRS), but our understanding of how inflammatory cytokines affect olfaction is limited.

To examine whether inflammatory cytokines are present in the olfactory cleft and whether they correlate with objective olfaction.

In this cross-sectional study, patients with CRS underwent quantitative olfactory testing using the Sniffin Sticks test to calculate a composite threshold discrimination identification (TDI) score from October 21, 2013, to November 12, 2015. Nasal mucus was collected using a sponge placed in the olfactory cleft for 5 minutes, and Cytometric Bead Array was used to measure secreted immunomodulatory products. Correlations between TDI score and secreted mediators were then calculated. Data analysis was performed from October 15, 2015, to December 17, 2015.

Composite TDI scores and mean secreted mediator levels in mucus from the olfactory cleft.

Thirty-four patients were enrolled (mean [SD] age, 57.3 [15.7] years; female, 21 [61.8%]; white, 26 [76.5]). The TDI scores were lower in patients with CRS with nasal polyps (CRSwNP) than in patients with CRS without nasal polyps (CRSsNP) (difference, 8.7; 95% CI, 2.5-15.0; P = .007). Interleukin (IL) 5 levels were inversely correlated with TDI scores in patients with CRSwNP and those with CRSsNP (mean [SE] β estimate, -46.56 [15.11]; P = .005), whereas IL-6, IL-7, and vascular endothelial growth factor A were positively correlated with TDI scores only in the CRSwNP cohort. Subscale olfactory TDI scores followed similar correlations to composite TDI scores.

In this study, inflammatory cytokines were found in mucus collected from the olfactory cleft. Levels of IL-5, in addition to other cytokines, were associated with objective olfactory function. Further inquiry is needed to establish the source of mucous cytokines and establish whether they play a causal role in olfactory loss.