Background The unified airway hypothesis proposes rhinitis and asthma are manifestations of a single inflammatory process. However, evidence regarding the association between allergic rhinitis/chronic rhinosinusitis (with or without nasal polyposis) and severe asthma is lacking. This systematic review aimed to identify the relationship between severe asthma and upper airway disease with the objective of understanding of how they are best jointly managed.
Methods We included relevant studies published between 2007 and 2017 in English. Studies were assessed for relevance and quality using predetermined criteria. Two authors independently reviewed the evidence using the GRADE system.
Results Thirteen studies were included; none were randomised controlled trials and five were non-randomised controlled studies. Four themes were identified across the literature: 1. the relationship between allergic rhinitis and severe asthma; 2. the impact of allergic rhinitis treatment on severe asthma; 3. the relationship between chronic rhinosinusitis and severe asthma; 4. the impact of chronic rhinosinusitis treatment on severe asthma. Evidence pertaining to each theme was assessed as low quality and Results varied. Three studies demonstrated weak evidence for increased prevalence or severity of allergic rhinitis in severe asthma. One study demonstrated no relationship. Six studies demonstrated weak evidence for the increased prevalence or severity of chronic rhinosinusitis in severe asthma, four studies demonstrated no relationship. Evidence from one uncontrolled study suggested symptoms of severe asthma may improve following combined surgical and medical management. Another uncontrolled study showed that allergic rhinitis symptoms improved following treatment of severe asthma with omalizumab.
Conclusions Though a unified airways model supports the relationship between rhinitis and asthma, evidence regarding severe asthma specifically is of low quality and Results are varied. Although it is likely that rhinitis symptoms improve alongside successful treatment of severe asthma, adequately powered randomised studies are necessary to substantiate this relationship.
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