Hierarchical clustering in evaluating inflammatory upper airway phenotypes; increased symptoms in adults with allergic multimorbidity

Abstract

Background: Inflammatory upper airway diseases cause significant morbidity. They include phenotypes with differ-ent treatment; allergic or non-allergic rhinitis (AR, nAR), and chronic rhinosinusitis with or without nasal polyps (CRSwNP, CRSsNP). In clinical practice, these phenotypes are often difficult to distinguish and may overlap. Objective: To evaluate if hierarchical clustering can be used to distinguish these phenotypes based on the presence of nasal polyps, off-seasonal allergic symptoms, and self-reported background characteristics-e.g. atopic dermatitis (AD); and to further analyse the obtained clusters. Methods: We studied a random sample of 74 CRS (chronic rhinosinusitis) patients, and a control group of 80 subjects without CRS with/without AR (tertiary hospitals, 2006-2012). All underwent interview and nasal examination, and filled a questionnaire. Variables regarding demographics, off-seasonal symptoms, and clinical findings were collected. Hierarchical clustering was performed, the obtained clusters were cross-tabulated and analysed. Results: Four clusters were identified; 1: “Severe symptoms and CRSwNP” (n = 29), 2: “Asymptomatic AR and controls” (n = 39), 3: “Moderate symptoms and CRSsNP” (n = 36), and 4: “Symptomatic and AD” (n = 50). Cluster 1 had most sinonasal symptoms, cluster 3 had a high prevalence of facial pain. The presence of AR did not distinguish CRS groups. Of the AR subjects, 51 % belonged to cluster 4, where AR with off-seasonal airway symptoms and AD predominated. Conclusion: Hierarchical clustering can be used to distinguish inflammatory upper airway disease phenotypes. The AR phenotype was subdivided by the presence of AD. Adult AR+ AD patients could benefit from active clinical care of the upper airways also off-season.