Pleural fluid agitation for improving the microbiologic diagnostic yield in pleural infection: a feasibility study.

Background: Pleural infection is a commonly encountered respiratory disease but in > 40% the underlying microbiologic etiology is unknown. This feasibility study aims to investigate whether pleural fluid agitation prior to sample aspiration is safe and can improve the diagnostic yield of microbiologic analysis.

Methods: Thirty adult patients with pleural infection, based on clinical, imaging and biochemical evidence, were included in this feasibility study. Ultrasound guided thoracentesis was performed with an initial standard aspiration sampling technique, followed by pleural fluid agitation into the pleural cavity for 3-5 cycles before collecting the agitated fluid. Coded samples were sent for biochemical and microbiologic analysis with culture in aerobic and anaerobic media.

Results: No complications were encountered with the pleural fluid agitation technique. Overall, 14 (46.6%) of patients had a positive pleural fluid culture. No yield discordance was noted between the standard and the agitated pleural fluid sampling techniques except for 1 extra agitated sample growing klebsiella pneumoniae and another agitated sample with mixed infection showing an additional anaerobic bacterial growth. Four (30.8%) of the 13 concordantly positive samples showed heavier bacterial growth in the agitated samples using semi-quantitative culture scoring.

Conclusion: Pleural fluid agitation was safe but didn't significantly add to the microbiologic yield in pleural infection. However, higher bacterial growth in almost one third of positive samples suggests a potential effect for further investigation in a larger study. Despite being safe, pleural fluid agitation resulted in no significant improvement in the microbiologic yield among pleural infection. However, agitated samples grew more bacteria in almost a third of the positive samples suggesting a signal for further investigation in a larger study.

Study registration: Clinicaltrials.gov - NCT05702580, 23/12/2022.