Analyzing pleural fluid attributes in SARS-CoV-2 infection: a systematic review

The characteristics of pleural fluid (PF) in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are poorly understood. During the pandemic, several cases of pleural effusion (PE) have been reported, but no clear conclusions have been reached regarding the features of this fluid. This systematic review aimed to analyze and summarize the available evidence on PF attributes in patients with SARS-CoV-2 infection.

Systematic literature search using the PRISMA methodology of studies describing PF characteristics of SARS-CoV-2 patients and treatment of PE.

Eighteen articles (32 patients and 37 PF samples) were included. Median age was 61 years (range, 25-81 years), male/female ratio 5.4:1. PE was predominantly unilateral (71.4%), with no distinction between one side and the other; it usually extended over 2/3 of the hemithorax (50%) and its appearance was variable [serous (50%), hematic or serohematic (28.1%) and purulent (21.9%)]. PF was exudative in 88.9% of cases, but with PF protein and PF/serum protein ratio values less than 3 g/dL and 0.5 in 36.7% and 54.5%, respectively. The pH and glucose values were less than 7.20 and 60 mg/dL in 28.6% and 24% of cases, respectively. The percentage of neutrophils (≥50%) was higher than that of lymphocytes/monocytes [12/26 (46.2%) vs. 7/26 (26.9%), respectively]. Polymerase chain reaction (PCR) on PF was positive for SARS-CoV-2 in 6/23 cases (26.1%) and for other pathogens in 8 (5 bacteria and 3 fungi). Almost all patients underwent thoracentesis and the medical treatment received by the cases with positive PCR for SARS-CoV-2 on PF varied. Patient follow-up was provided in 25 cases and 10 cases died (40%).

PE from coronavirus disease 2019 (COVID-19) infection is more frequent among males aged 50-80 years, generally unilateral and large. Its appearance is variable, with features of lactate dehydrogenase (LDH)-discordant exudate, usually predominantly neutrophilic, with treatment like that of any other PE. PE from COVID-19 infection is a poor prognostic sign and associated with worse mortality.