Abstract Introduction Bronchoalveolar lavage (BAL) is a valuable diagnostic tool used to assess various conditions such as infectious, neoplastic or inflammatory processes in Pulmonology. It is a minimally invasive, safe, cost effective, and well tolerated procedure that yields a significant diagnostic yield. Many supplementary tests further expand the diagnostic yield of the BAL. Often, it is combined with differential cell counts, cytology, cultures, polymerase chain reaction, or specific test for mycobacterium tuberculosis. Microbial cell free DNA testing (Karius Test) was previous only available through a blood sample, however, at the start of this year, it became available to run on a BAL sample. This helps identify pathogens causing pneumonia and other lung infections, especially in immunocompromised patients. Case Description 17 year old female with several month history dry cough and 10-15 pound weight loss who presented with worsening dyspnea on exertion. No travel history was reported, however patient had close contact with a family member who spent considerable time in Costa Rica. Due to worsening chronic cough and fatigue, a chest xray was ordered which showed hyperinflation with emphysematous changes in the upper lobes. CT of the chest was suggestive of cavitary lung disease, and Quantiferon gold was negative. Patient underwent Bronchoscopy and BAL that was sent off for Karius testing. While awaiting results, Anti-TB regimen was initiated alongside Meropenem for suspected pneumonia. Karius testing yielded positive DNA for Mycobacterium Kansasii. Antibiotics were switched to Azithromycin, Rifampin, Ethambutol, and Pyrazinamide. Discussion Bronchoalveolar lavage is a commonly used diagnostic tool in evaluation of lung disease. BAL alone has a good diagnostic yield, but when combined with other tests, increases significantly. The recent development of microbial cell free DNA testing in combination with BAL significantly adds to the diagnostic value. It is especially useful in determining infectious etiologies in immunocompromised children whose blood cultures may sometimes be negative. Karius Focus was designed for detection and classification of over 500 pathogens associated with lung infections. It utilizes BAL fluid requiring only 1 mL of sample and detects key pathogens such as Legionella, Coxiella, and Mycobacterium species. This new methodology is designed to quickly identify the etiology of lunch infections, enhancing patient care and treatment outcomes. Conclusion Bronchoalveolar lavage and Karius alone offer high diagnostic yield, but when combined together increases sensitivity, allowing for an increased number of pathogens to be identified. Further studies should be done to accurately report on diagnostic capabilities. This abstract is funded by: Self
Blanco et al. (2026) studied this question.