Smell in cystic fibrosis

In cystic fibrosis (CF), the most frequent life threatening inherited disease in Caucasians, sinonasal mucosa is regularly affected by defective mucociliary clearance. This facilitates pathogen colonization into CF airways and causes frequent symptoms of rhinosinusitis, including an impaired sense of smell. Despite probable effects on nutrition and overall health, CF-rhinosinusitis is little understood: CF-associated smelling deficiencies reported in literature vary between 12 and 71 %. The aim of this study was to assess olfactory and gustatory function in relation to sinonasal symptoms and sinonasal colonization, and lung function and nutrition. Thirty-five CF patients of different ages were compared to 35 age-matched healthy controls. Olfactory function was assessed by 'Sniffin'Sticks', gustatory qualities by "Taste-strips", and symptoms by sino-nasal outcome test 20 (SNOT-20). Normosmia was found in 62.8 % of healthy controls but only in 28.6 % of CF patients. In contrast the majority of CF patients exhibited a smell loss; almost 62.9 % of them were hyposmic, and 8.6 % functionally anosmic. Importantly, reduced olfactory function only affected odor thresholds, which were significantly increased in CF, not odor identification. This suggests that the olfactory dysfunction in CF results from the olfactory periphery due to either problems in conduction and/or a functional lesion due to the inflammatory process. SNOT-20 scores increased continuously from normosmic to hyposmic and anosmic CF patients (means 7.2/11.1/28.3 points). Neither sinonasal pathogen colonization, gender, pulmonary function, nor allergy or sinonasal surgery appeared to have significant effects on olfactory function and taste. Olfactory disorders are considerably more frequent in CF patients than in age-matched healthy controls. Assessing these parameters within CF-routine care should be considered because of their importance to nutrition and, thus, overall therapy outcome.