Late Breaking Abstract - Response to antibiotic therapy for pulmonary exacerbations in patients with primary ciliary dyskinesia–an ongoing study

Primary ciliary dyskinesia (PCD) is a rare disease caused by mutations in genes important for ciliary function and assembly. Ciliary dysfunction leads to an impaired mucociliary clearance, resulting in chronic progressive muco-obstructive lung disease. First causative therapies are underway, but clinical outcome parameters are not well defined. Thus we aimed to detect changes in lung function to systemic antibiotic therapy in PCD patients with a pulmonary exacerbation (PEx). Genetically confirmed PCD patients with PEx requiring systemic antibiotic treatment were included in our prospective observational study. Spirometry and multiple-breath washout were measured within 72h at PEx and 2-4weeks after the end of antibiotic treatment (FU) and lung clearance index (LCI), percent predicted forced expiratory volume in one second (ppFEV1), sputum and clinical data were collected. Pre-PEx values were retrospectively obtained from routine visits within 3 months prior to PEx in stable condition. 21 PCD patients (86% female) with PEx were included. Median age at PEx was 25.3(IQR, 10.7–61.0) years. 8(38%) participants were minors. Median ppFEV1 at pre-PEx was 65.5(IQR, 49.2–90.5), 60(IQR, 46.4–71.3) at PEx and 66.5(IQR, 56.5–86.5) at FU. ppFEV1 was significantly lower at PEx (−5.1%; IQR,-14.8 to-0.02, p=0.0011) compared to pre-PEx and significantly improved at FU compared to PEx (6.8%; IQR, 2.4-13.5,p=0.0005). There was no significant change in LCI; median LCI at pre-PEx was 11.1 (IQR, 8.5–12.1), at PEx 10.6 (IQR, 9.3–12.5) and at FU 10.0 (IQR, 9.2–11.8). Thus, ppFEV1 seems to be more sensitive than LCI to detect lung function changes at PEx and after antibiotic treatment in PCD