Olfactory performance in Cystic Fibrosis patients

Background: Cystic Fibrosis (CF) is characterized by multiorgan manifestations which include chronic rhinosinusitis (CRS) and nasal polyposis. CRS is one of the most common causes of sinonasal–related olfactory dysfunction. The principal symptoms of rhinosinusitis are chronic nasal congestion, rhinorrea, mouth breathing, anosmia/hyposmia, and facial pain. Aims: Olfactory performances in CF patients have not been studied. Because of a large percentage of CF patients present CRS we evaluated the olfactory performance in: i) CF patients with CRS without polyps; ii) age-matched healthy controls. Methods: We enrolled: - group I: 20 CF patients with CRS without polyps with different mutations (mean age: 31.5±9.4 years); - group II: 20 age-matched healthy volunteers (mean age: 29.6±6.9 years); There were not statistical differences between the two groups with respect to age, sex, and the distribution of age groups. All cases were not smokers. Subjects should not assume food or beverages other than water within 6 hours of the test. Subjects with acute nasal infection and/or nasal polyps were excluded. All subjects underwent the Sniffin’Sticks (Burghart Medical Technology) (SS) olfactory test to assess the olfactory performance. SS is a test of nasal chemosensory performance based on pen-like odor-dispensing devices. The SS test includes three olfactory evaluations: - odor threshold (T) - odor discrimination (D) - odor identification (I) The result of the three evaluations is the TDI score. Based on the TDI score: - anosmia was defined by a TDI<16 - hyposmia was defined by 16≤TDI <25 for subjects younger than 16, by 16≤TDI <29 for those aged between 16 and 35, and by 16≤TDI <28 for those older than 53. Results: Group I Group II Normosmic 10% 70% Hyposmic 60% 15% Anosmic 15% 0% Borderline (hypo-normosmic) 15% 15% Only 5 of our CF patients complained olfactory impairment. CF patients (Group I) presented mean odor identification of 10.6±3.36, mean odor discrimination of 10.1±2.86, mean odor threshold of 2.34±2.86, mean TDI score of 23.35±7.04. Healthy controls (Group II) presented mean odor identification of 13.30±1.17, mean odor discrimination of 12.50±1.82, mean odor threshold of 7.28±2.17, mean TDI score of 25.8±2.02. Results of single odor identification, discrimination and threshold SS differed with statistical significance between the CF patients (Group I) and healthy controls (Group II) (p<0.001). Conclusions: The assessment of olfactory performance in CF patients is of utmost interest, because olfactory deficiency impairs the overall course of this life threatening disease, decreasing appetite and aggravating nutritional problems. In this study, we found a significant frequency of smelling disorders in CF patients and in particular a major impairment of odor threshold than of odor identification and discrimination. In conclusion, our data suggest that the olfactory deficiency in CF patients can result from dysfunction at the level of the olfactory periphery due to either problems in conduction and/or a functional lesion due to the inflammatory process. Indeed in CF patients the olfactory periphery is characterized by impaired mucociliary clearance, caused by a defective ion channel function of sino-nasal mucosa and mucosal inflammation with thickened mucus. From a perspective point of view, it seems that therapies improving the mucociliary clearance might recover olfactory performance in CF patients with CRS. Moreover this olfactory test could represent a new tool to help clinicians in the follow-up of treated patients.