Extracellular DNA in sputum is associated with pulmonary function and hospitalization in patients with cystic fibrosis

Elevated extracellular DNA levels are found in the sputum of patients with cystic fibrosis (CF). However, studies investigating the association of extracellular DNA with CF severity are scarce.

To evaluate the association of extracellular DNA levels with pulmonary function, antibiotic use, and hospitalization in CF patients.

This cross-sectional study included CF patients aged ≥5 years who were clinically stable and produced spontaneously expectorated sputum. Extracellular DNA in sputum was quantified, and extracellular DNA networks were seen with immunofluorescence microscopy. Also, cell death profile was assessed. Data on pulmonary function, airway colonization, antibiotic use, and hospitalization in the previous year were collected. Patients were divided into two groups based on median DNA level.

Thirty-three patients were included. Their mean age was 16.3 ± 6.2 years, mean forced expiratory volume in the first second (FEV₁) was 67.0 ± 26.7 (% of the predicted), and mean DNA level was 241.9 ± 147.2 μg/mL. There were significant correlations of DNA level with FEV₁ (r = -0.60; p < 0.001) and forced vital capacity (r = -0.59; p < 0.001). Moreover, patients with higher DNA level (>243.0 μg/mL) had lower FEV₁ (52.1 ± 27.8% vs. 81.1 ± 16.2%; p = 0.001) and required more hospitalizations (68.8% vs. 35.3%; p = 0.05). Additional findings were the presence of extracellular DNA networks and low rates of necrosis and apoptosis.

Elevated extracellular DNA levels in CF sputum are associated with reduced pulmonary function and increased hospitalizations.