Objective: The aim of the study was to clarify the possibility of using pleural fluid levels of soluble IL-2 receptor (sIL-2R) and type III procollagen N-terminal aminopeptide (PIIIP) for differentiating tuberculous, carcinomatous and parapneumonic pleural effusions.
Methodology: Fifty patients with pleural effusions were investigated retrospectively. The pleural effusions were due to tuberculosis (n = 11), carcinoma (n = 22), pneumonia (n = 9) and heart failure (n = 8). The concentrations of sIL-2R and PIIIP were measured in pleural effusion using commercially available kits.
Results: Soluble IL-2 receptor concentrations were highest in the patients with tuberculosis (6,856 +/- 3,212 U/mL), followed by those with carcinoma (4,680 +/- 1,872 U/mL), pneumonia (2,227 +/- 525 U/mL) and heart failure (1,439 +/- 244 U/mL). Significant differences were found between tuberculosis and carcinoma (P = 0.023), carcinoma and pneumonia (P = 0.015), and pneumonia and heart failure (P = 0.002) groups. Type III procollagen N-terminal aminopeptide concentrations were higher in the patients with tuberculosis (262.5 +/- 157.9 U/mL) and pneumonia (257.0 +/- 96.7 U/mL) than in those with carcinoma (48.0 +/- 27.7 U/mL) and heart failure (10.9 +/- 5.6 U/mL). Significant differences were found between tuberculosis and carcinoma (P < 0.001) and pneumonia and carcinoma (P < 0.001). To differentiate effusions, the cutoff points of sIL-2R (2,980 U/mL) and PIIIP (110.0 U/mL) were obtained from the highest concentration in the pneumonia group and in the carcinoma group, respectively. Using these criteria, the sensitivities for differentiating tuberculous, carcinomatous, and parapneumonic effusions were 90.9, 86.4 and 88.9%, respectively, with 100, 95 and 100% specificity, respectively.
Conclusions: The simultaneous determination of sIL-2R and PIIIP concentrations in pleural effusions may be clinically useful in differentiating tuberculous, carcinomatous, and parapneumonic effusions. Further assessments are required to determine the broad clinical application of this assay.