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Title: Characterisation of non-adherence and persistent symptoms in difficult asthma
Author: McNicholl , Diarmuid Michael
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2013
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Background: Difficult asthma (uncontrolled symptoms despite standard treatment) is not always a result of asthma severity. Factors such as nonadherence are important contributors to poor control, yet challenging to detect. Aims and Methods: 1) Assess the relationship between FeNO and ICS adherence at presentation to a difficult asthma service. 2) Develop a test for non-adherence using fractional exhaled nitric oxide (FeNO) suppression by comparing the response of adherent and non-adherent patients to directly observed inhaled corticosteroid (DOICS) treatment. Validate this test against a composite adherence measure. 3) Retrospectively examine the utility of cardiopulmonary exercise testing (CPX) to define the cause of persistent symptoms out of keeping with clinical parameters. • Results: 1) No significant correlation between FeNO and ICS prescription filling at clinic presentation was evident (n=146, r = -0.11 , P = 0.2). 2) After 5 days of DOICS non-adherent (n=9) compared with adherent patients (n=13) had a greater reduction in FeNO (p=0 .02) and a test for nonadherence (AUC=0.86) was defined. Test validation (n=40) against a composite measure of adherence resulted in: sensitivity 0.67, specificity 0.95, NPV 0.78, PPV 0.92. The test identified 3 patients who admitted nonadherence on interview but had excellent prescription filling. Six patients were incorrectly identified as adherent to ICS but 4 were adherent with oral steroids and 1 with Omalizumab. 3) After systematic evaluation 39 patients underwent CPX with the following features identified: hyperventilation (n=14), exercise-induced ' bronchoconstriction (n=8), submaximal test (n=8), normal test (n=8) ventilatory limitation (n=7), deconditioning (n=2), cardiac ischemia (n=I). After CPX patients without pulmonary limitation had their ICS dose reduced (txO.001) and additional medication withdrawn (n=7). Conclusions: FeNO at presentation to a difficult asthma service cannot be used as an indicator of non-adherence. However, FeNO suppression following DOICS provides an objective test to distinguish adherent from nonadherent patients with difficult asthma. CPX can identify the primary mechanism of persistent breathlessness in difficult asthma and facilitate steroid reduction when asthma is not the cause.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available