Combined analysis of C-reactive protein in pleural fluid and serum is effective in the differential diagnosis of exudative pleural effusions

Abstract

Background: Exudative pleural effusion (EPE) is one of the common pleural manifestations of various diseases. Differential diagnosis of EPE is imperative clinically as it identifies different causes of EPE, thereby, enabling effective treatments. Thoracoscopy is a useful tool for differential diagnosis of EPE; however, some patients refuse thoracoscopic examination due to its invasive nature. In addition, the specificity and sensitivity of existing routine tests of EPE are unsatisfactory. Therefore, there is a great need to establish an effective method for the differential diagnosis of EPE.Methods: This study was a single-institution retrospective analysis of diagnostic efficiency of C-reactive protein (CRP) and procalcitonin (PCT) between March 2018 and September 2018. A total of 87 patients diagnosed with EPE were enrolled. All participants underwent diagnostic thoracentesis. The EPE was examined using biochemical, routine, microbiological, and cytological methods. Pathological cytology detection was necessary for those suspected of malignant PE. Benign PE originates in patients with pneumonia, empyema, and tuberculosis. The levels of CRP and PCT in EPE and serum were measured before treatment.Correlation analysis and receiver-operating characteristic (ROC) curve analysis were conducted to determine the underlying relationship between levels of CRP and PCT, and for differential diagnosis. Results:The ROC analysis showed that the sensitivity and specificity for the analysis of pleural fluid CRP (p-CRP) were higher (cut-off: 17.55 pg/mL; sensitivity: 75.00%, specificity: 83.90%) than that of serum CRP (s-CRP, cut-off: 23.90 pg/mL; sensitivity: 71.00%, specificity: 80.4%) in the differential diagnosis for EPE. However, the analysis of pleural fluid PCT (p-PCT) and serum PCT (s-PCT) did not demonstrate correlations with EPE. Combined analysis of p-CRP (cut-off: 17.55 mg/dL) with s-CRP (cut-off: 23.9 pg/mL) showed the highest diagnostic accuracy (88.4%) in diagnosing infectious EPE. Conclusions:The data support the close relationship between combined analysis of p-CRP with s-CRP and effective and accurate differential diagnosis of EPE, due to its higher sensitivity and specificity. However, as a highly sensitive marker for diagnosing bacterial infections, neither s-PCT nor p-PCT, showed correlations with the differential diagnosis of EPE.

The Role of Pleural Fluid C-Reactive Protein in the Diagnosis of Exudative Pleural Effusions

“…Pleural fluid neutrophils were predominantly observed in the empyema and parapneumonic groups, while pleural fluid lymphocytes were predominant in tuberculous and malignant effusion. These findings are comparable with the results obtained by Watanabe et al [ 5 ] and Qu et al [ 16 ]. Pleural fluid ADA level was significantly higher in tuberculous effusion [87.1 (68.1-121.15)] than in other causes of exudative effusion.…”

“…Pleural fluid ADA level was significantly higher in tuberculous effusion [87.1 (68.1-121.15)] than in other causes of exudative effusion. Studies by Qu et al [ 16 ] and Radhakrishnan et al [ 4 ] also reported that the pleural fluid ADA level was significantly higher in the tuberculous effusion group.…”

“…In our study, patients were in the age range of 20-79 years, with males predominantly affected compared to females. The study by Qu et al [ 16 ] involving 87 patients with exudative pleural effusion also reported that males were more affected (62 cases) than females (25 patients). In our study, the most common cause of exudative effusion was TB (80%), followed by parapneumonic and malignant effusion in 8% and 7% of patients, respectively.…”

“…Light's criteria are currently used to differentiate transudative from exudative effusion [ 2 ]. Exudative pleural effusion is clinically common in various respiratory disorders, and its further sub-classification mainly relies on pleural fluid routine and biochemical, cytological, and pathological examinations [ 16 ]. However, the sensitivity and specificity of the above tests are unsatisfactory for achieving a specific diagnosis of exudative effusion.…”

Evaluation of the efficiency of the systemic immune‐inflammation index in differentiating parapneumonic effusion from empyema

“…In an adult study conducted from Turkey in the empyema group, WBC, CRP, ALC, and LMR were found to be significantly higher than PPE group and LMR was more sensitive than other markers. 13 Qu et al 14 reported that the neutrophil percentage and CRP level of the empyema group were significantly higher than the PPE group, and the lymphocyte percentage was significantly lower in the empyema group. In a study evaluating 477 pediatric patients with CAP, it was reported that WBC count, ANC, CRP and procalcitonin are generally not useful to discriminate nonsevere from severe disease in children with CAP, although CRP and procalcitonin may have some utility in predicting the most severe outcomes.…”