Exhaled nitric oxide in cystic fibrosis patients with allergic bronchopulmonary aspergillosis

An investigation into biomarkers for the diagnosis of ABPA and aspergillus disease in cystic fibrosis

BACKGROUND

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity lung disease due to Aspergillus fumigatus (Af) which occurs in 10% of patients with cystic fibrosis (CF). ABPA is associated with increased morbidity and accelerated lung function decline; however, existing diagnostic criteria are nonspecific and diagnosis remains challenging. As ABPA is driven by Th2 inflammation, the aim of this study was to evaluate exhaled nitric oxide (FE _NO ), eosinophilic cationic protein (ECP), peripheral eosinophil count, and bronchodilator response (BDR) in patients with CF.

METHODS

A prospective observational cohort study of pediatric CF patients in a tertiary center. Patients had a clinical and serologic ABPA assessment, FE_NO , serum ECP, peripheral eosinophil count, and assessment of BDR. Patients were stratified into three groups; ABPA, Af sensitized (AFS), and non-ABPA non-Af-sensitized (non-AFS).

RESULTS

A total of 62 patients were included in the study: 13% ABPA, 19% AFS, and 68% non-AFS. Mean FE_NO was higher in the ABPA group at 37.8 ppb compared to AFS 15.1 ppb (P = .05) and non-AFS 13.7 ppb (P = .04). Mean peripheral eosinophil count in ABPA group was also higher at 1000 cells/uL, compared to AFS 221 cells/uL (P = .03) and non-AFS 220 cells/uL (P = .03). Mean BDR in ABPA group was 13% compared to 5.5% in non-AFS (P = .01). Serum ECP was higher in patients with ABPA positive compared to the other groups, although this was not statistically significant.

CONCLUSION

In children with cystic fibrosis, FE_NO and peripheral eosinophil counts are elevated in ABPA compared to those that are just sensitized to Aspergillus and may serve as useful diagnostic tests.

Noninvasive biomarkers of airway inflammation in cystic fibrosis

PURPOSE OF REVIEW

Airway inflammation plays a central role in the lung disease of cystic fibrosis (CF). Biomarkers of inflammation may be useful for monitoring disease progression and evaluating response to therapy. Much of our knowledge of the chronic inflammatory process in the CF airway derives from studies of bronchoscopy and bronchoalveolar lavage. A number of noninvasive approaches have been recently developed to more readily assess airway inflammation including sputum induction, collection of exhaled air, analysis of systemic markers of inflammation, and computed tomography imaging.

RECENT FINDINGS

While measurements of biomarkers of inflammation continue to advance our understanding of the underlying disease process, there is as yet no established role for these markers in clinical practice. This review summarizes the current state of knowledge of various inflammatory markers relevant to CF lung disease, with an eye towards application as surrogate outcome measures in CF clinical trials.

SUMMARY

It is hoped that biomarkers obtained by noninvasive means will be useful in determining specific pathways of injury (ie, oxidative or proteolytic) in individual persons with CF and in assessing response to antiinflammatory treatments.