(465) A Breath Test for P. aeruginosa? The Results Look Promising…

Background: Chronic Pseudomonas aeruginosa (Pa) infections are associated with progressive lung function decline and increased risk of mortality in persons with CF (PwCF) [1]. Early detection of Pa is paramount for successful treatment [2], but we are arriving at a diagnostic cliff as we lose access to sputum due to the success of highly effective modulator therapies; alternative airway samples (e.g., oropharyngeal swabs) have poor sensitivity for Pa lung infections [3]. We previously reported preliminary results from a clinical study titled “IMproving P. Aeruginosa deteCTion with Breath-based diagnostics” (IMPACT-Breath; NCT04735952) in which we showed that breath biomarkers are sensitive and specific for Pa infections, including in the setting of Staphylococcus aureus (Sa) co-infections. In this study we verified the reproducibility of our biomarkers using breath samples collected from independent subjects and analyzed at an independent site.

Methods: Breath samples (n=166) from 156 PwCF were analyzed at two sites (Site 1, n=82 samples, 80 subjects; Site 2, n=84 samples, 76 subjects) using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry. Sputum was also collected concurrently and cultured for typical CF lung pathogens, including Pa and Sa. VOCs associated with Pa infection (with and without co-infection) in the Site 1 breath samples were identified using Random Forest (RF) classification models and verified using the independent samples analyzed at Site 2.

Results: For samples analyzed at Site 1, sputum culture detected Pa (n=15), Sa (n=30), and Pa/Sa co-infection (n=10); 27 samples had neither. Site 2 verification samples consisted of Pa (n=11), Sa (n=27), and Pa/Sa co-infection (n=6); 40 samples had neither. RF models classified Site 1 breath samples as Pa+/– with ≥98% sensitivity/specificity using as few as 10 VOCs (Table). The inclusion of Sa co-infected patients lowered Pa classification accuracy to 91% sensitivity/specificity. Using the 10 most discriminatory VOCs for each model to classify the Site 2 samples resulted in ≥89% sensitivity and 100% specificity for Pa samples, with and without Sa co-infection.

Conclusions: We have tested our ten Pa breath biomarkers in independent subjects, whose breath samples were analyzed at an independent site. These results verify that a small subset of breath biomarkers are highly predictive for detecting Pa infection, regardless of Sa
co-infection.

Acknowledgements: This work was supported by the Cystic Fibrosis Foundation [Hill17P0, Hill18A0-CI] and the National Institutes of Health [R56HL139846].

References: [1] Gibson RL, Burns JL, Ramsey BW. Pathophysiology and management of pulmonary infections in cystic fibrosis. Am J Respir Crit Care Med. 2003;168:918.
[2] Ratjen F, Moeller A, McKinney ML, Asherova I, Alon N, Maykut R, Angyalosi G, Early Study Group. Eradication of early P. aeruginosa infection in children < 7years of age with cystic fibrosis: The early study. J Cyst Fibros. 2019;18:78.
[3] Seidler D, Griffin M, Nymon A, Koeppen K, Ashare A. Throat swabs and sputum culture as predictors of P. aeruginosa or S. aureus lung colonization in adult cystic fibrosis patients. PLoS One. 2016;11:e0164232.