Factors affecting bacterial culture positivity in specimens from bronchoscopy in patients with suspected lung cancer

Bronchoscopy is important to diagnose lung cancer. However, some patients who undergo bronchoscopic procedures develop respiratory tract infections. Little is known about the proportion of pathogen-positive results in bacterial cultures from diagnostic bronchoscopy samples in patients with suspected lung cancer. This study aimed to determine the rate of positive bacterial cultures after diagnostic bronchoscopy in patients with suspected lung cancer and the relationship among culture results, clinical characteristics, and respiratory tract infections.

We retrospectively reviewed the medical records of all immunocompetent patients who underwent bronchoscopy and had culture and histological samples for the diagnosis of peripheral pulmonary lesions from September 2012 to August 2014 at the National Cancer Center in Tokyo. We analyzed data and classified radiological lesions into the following categories: calcifications, cavitations, low-density areas, margin irregularities, and satellite nodules.

The study population consisted of 328 patients (median age, 69 years). We found that 65.9% of patients had malignant lesions and 4.2% of patients had positive cultures for pathogenic bacteria. The number of calcifications (p = 0.002, 95% CI: 2.17-41.10) was significantly higher in patients with positive bacterial isolates, according to the multivariate analysis, and bacterial culture positivity was not associated with the development of respiratory complications after bronchoscopy. Of the three patients with respiratory complications, all presented with cavitations.

Because of the low prevalence of positive bacterial cultures in patients with suspected lung cancer, bacterial culture may be limited to specific patients, such as those with calcifications. Lesions with cavitation warrant close monitoring.