Diagnostic utility of soluble triggering receptor expression on myeloid cells-1 in complicated parapneumonic pleural effusion

Background: The differentiation between complicated parapneumonic effusions (CPPE) or empyema, which require chest tube drainage, and uncomplicated parapneumonic effusions (UCPPE), which respond to antibiotic therapy alone, is sometimes unclear. Delay in diagnosis results in substantial delay in the commencement of treatment and may contribute to the high mortality of this infection. The aim of the study: Evaluation of the utility of soluble triggering receptor expression on myeloid cells-1 (sTREM-1) as an early marker in the diagnosis and management of complicated parapneumonic effusions and empyema. Patients and methods: This study included 58 patients who were diagnosed as having PPE and admitted to the Chest Department, Zagazig University Hospitals during the period from March 2012 to March 2013. Patients were diagnosed PPE if they had a pleural effusion and showed one or more clinical manifestations typical of pneumonia, including acute febrile illness, sputum production, chest pain, leukocytosis and infiltrate(s) on chest X-ray. They were divided into two groups. Group (1): Complicated parapneumonic effusion (22 patients), according to at least one of the following criteria on pleural fluid examination: macroscopic pus, presence of organisms on Gram-stain or culture, fluid pH < 7.2 with normal peripheral blood pH, or fluid glucose concentrations <40 mg/dL. Group (2): Uncomplicated parapneumonic effusion (36 patients), according to the following criteria: pleural effusion associated with a non purulent pleural fluid, negative fluid microbiological studies; fluid pH > 7.2 with normal peripheral blood pH and fluid glucose >40 mg/dL. Exclusion criteria: A history of pleural disease or any underlying disease that could potentially cause pleural effusions, such as tuberculosis, malignancy, heart failure, systemic lupus erythematosus and chronic renal failure, were excluded. Pleural fluid samples were examined for level of sTREM-1, pH, LDH and glucose. The sTREM-1 levels were expressed as pg/mL. Microbiological studies included: Gram and Ziehl–Neelsen stains and cultures on conventional media for aerobic and anaerobic micro-organisms in the pleural fluid samples. Results: The median sTREM-1 level in pleural fluid was significantly higher in the bacterial PPE (688 ± 398 pg/mL) than in the non-bacterial PPE (45 ± 79 pg/mL). The cut-off value of pleural fluid sTREM-1 for diagnosis of bacterial PPE was 130 pg/mL with 93% sensitivity and 92% specificity, while it was 7.237 for pleural fluid pH with 91% sensitivity and 96% specificity and 640 mg/L for pleural fluid glucose with 92% sensitivity and 86% specificity and 800 IU/L for pleural fluid LDH with 81% sensitivity and 90% specificity. In conclusion: Combination of classical criteria with pleural fluid sTREM-1 could be useful in discrimination between nonpurulent complicated and non complicated parapneumonic pleural effusions and hence early pleural drainage in patients with complicated parapneumonic effusions which may affect disease outcome