The potential role of bronchial challenge testing to identify overtreatment of community managed asthma

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Introduction: Bronchial hyperresponsiveness is a defining feature of asthma and is measured by bronchial challenges which are not routinely used in primary care. Aim: To evaluate the potential role of direct (methacholine) and indirect (mannitol) challenge testing in primary care. Methods: Community managed asthmatics were identified by the Health Informatics Centre (HIC) and invited to take part in the study. At screening the following tests were carried out: spirometry, methacholine and mannitol challenge; FeNO, Asthma Control Questionnaire (ACQ-6) and Asthma Quality of Life Questionnaire (MiniAQLQ). Results: 3388 asthmatics were identified by HIC with 423 positive responses and 123 completing the study. 70% had either a positive methacholine (PC 20 <8mg/ml) or mannitol challenge (PD 15 <635mg) and 30% were non-responsive to both challenges. 14% of methacholine responders were negative to mannitol and 16% of mannitol responders were negative to methacholine. Spirometry, FeNO, ACQ and AQLQ were significantly better in the non-responder group who were exposed to high ICS dose and frequent LABA. Patient characteristics according to bronchial challenge response Responders N=86 Non-responders N=37 P-value Age(yrs) 46(43-49) 51(47-55) 0.047 ICS dose(BDP equivalent,ug) 500(400-1000) 1000(400-1000) 0.08 LABA(%) 64 68 0.70 FEV1(%) 88(85-91) 100(95-104) <0.001 FeNO(ppb) 26(21-32) 16(13-20) 0.003 ACQ-6 1.07(0.90-1.24) 0.55(0.32-0.77) <0.001 MiniAQLQ 5.59(5.37-5.81) 6.05(5.78-6.33) 0.015 Data presented as means(95% CI) except ICS dose as median(IQR) Conclusions: We found that 30% of patients with community managed asthma were challenge negative and also appeared to be overtreated, in turn suggesting the need for supervised step-down.

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