Anti-Pseudomonas aeruginosa IgG antibodies and chronic airway infection in bronchiectasis

Identification of chronic Pseudomonas aeruginosa (PA) infection is important in the management of bronchiectasis, but requires repeated sputum sampling. We hypothesized that serum anti-PA IgG antibodies could diagnose chronic PA infection at a single visit.

Clinically stable bronchiectasis patients were studied prospectively. Chronic PA infection was defined as 2 or more positive sputum samples at least 3 months apart and/or failure to clear PA following eradication treatment. Baseline serum anti-PA IgG was determined by a validated ELISA kit.

A total of 408 patients were included. Sixty of them (14.7%) had chronic PA infection and had higher anti-PA IgG levels (median 6.2 vs. 1.3 units, p < 0.001). Antibody levels showed direct significant correlations with exacerbation frequency, the bronchiectasis severity index and sputum inflammatory markers. Fifty-seven patients with chronic PA infection had a positive test, giving 95% sensitivity, 74.4% specificity and AUROC of 0.87. During follow-up, 38 patients had a new PA isolation. Eradication at 12 months was achieved in 89.5% of subjects with a negative antibody test and 15.8% of patients with a positive test.

Anti-PA IgG test is highly accurate to detect chronic PA infection in bronchiectasis patients. In addition, it may be a marker of disease severity and treatment response.