Determination and Comparison of the Pathogen Spectrum Evaluated by Microbial Culture and Multiplex PCR During Bronchoscopy with Regard to Clinical Utility of Routine Bronchial Wash in Patients with Various Pulmonary Diseases

Background/Objectives: Bronchial wash for microbiological cultivation and/or multiplex polymerase chain reaction (PCR) is often routinely performed during bronchoscopy independent of the indication for bronchoscopy. This study aimed to determine and compare the pathogen spectrum evaluated by culture and PCR in bronchial secretion samples with regard to the underlying lung pathology. Methods: In this retrospective analysis, microbiological results from bronchial washes performed from February 2022 to September 2022 were collected in 245 patients (48.2% male, mean age 63.0 ± 13.9 years). Samples were assessed for bacteria/fungi culture and reported depending on the underlying pathology. Additional PCR was performed in 216 patients and compared to the results of the culture. Results: Cultivation and PCR revealed positive results in 20% and 24.5% of the cases, respectively. Microbiological culture most likely revealed a positive result in patients with hemoptysis (44.4%) and pulmonary infections (29.6%) among various indications for bronchoscopy, and PCR most likely identified a pathogen in patients with hemoptysis (66.7%) and COPD (36.4%). Active smoking and an increased CRP were revealed as significant predictors for a positive culture (p < 0.0001 and p = 0.021). The concordance rate between culture and PCR for identifying pathogenic microorganisms was 84.3%, resulting in a moderate agreement (kappa coefficient 0.54 [95% CI: 0.34-0.68]). Conclusion: PCR and culture moderately agreed, showing additional PCR testing only to be beneficial if restricted to proper indications, providing rapid diagnosis and therefore leading to immediate therapeutic decisions.