The Use of a Novel Quantitative Marker of Echogenicity of Pleural Fluid in Parapneumonic Pleural Effusions

BACKGROUND: Thoracic ultrasound is an essential tool in the daily clinical care of pleural effusions and especially parapneumonic pleural effusions (PPEs), in terms of diagnosis, management, and follow-up. Hypoechogenicity index (HI) is a quantitative marker of pleural fluid echogenicity. We aimed to examine associations of HI with pleural inflammation in patients with PPE. METHODS: All patients included underwent a thoracic ultrasound with HI determination at the first day of their admission for a PPE. Thoracentesis was performed in all patients. Demographics, laboratory measurements, and clinical data were collected prospectively and recorded in all subjects. RESULTS: Twenty-four patients with PPE were included in the study. HI was statistically significantly correlated with intensity of inflammation as suggested by pleural fluid LDH (p < 0.001, r = −0.831), pleural fluid glucose (p=0.022, r = 0.474), and pleural fluid pH (p < 0.001, r = 0.811). HI was correlated with ADA levels (p=0.005, r = −0.552). We observed a statistically significant correlation of HI with pleural fluid total cell number (p < 0.001, r = −0.657) and polymorphonuclears percentage (p=0.02, r = −0.590), as well as days to afebrile (p=0.046, r = −0.411), duration of chest tube placement (p < 0.001, r = −0.806), and days of hospitalization (p=0.013, r = −0.501). Discussion. HI presents a fast, easily applicable, objective, and quantitative marker of pleural inflammation that reliably reflects the intensity of pleural inflammation and could potentially guide therapeutic management of PPE.