A novel diagnostic method for distinguishing parapneumonic effusion and empyema from other diseases by using the pleural lactate dehydrogenase to adenosine deaminase ratio and carcinoembryonic antigen levels
Light, Richard W.
Pleural effusions are a common medical problem not only for pulmonologists but also for general physicians, often needing thoracentesis for a definite diagnosis. However, thoracentesis cannot always reveal malignant cells or microbiological evidence. In this context, we prospectively enrolled a total of 289 patients with pleural effusions due to diverse etiologies: parapneumonic effusion (PPE) (63), empyema (22), tuberculous pleural effusion (TBPE) (54), malignant pleural effusion (MPE) (140), or chronic renal failure (CRF)/congestive heart failure (CHF) (10). The MPE group consisted of lung cancer (adenocarcinoma, n=90; squamous cell carcinoma, n=5; small cell carcinoma, n=4), malignant lymphoma (n=17), malignant mesothelioma (n=11), malignant melanoma (n=3), and metastasis from other organs (n=10). This study demonstrated that the pleural lactate dehydrogenase (LDH) to adenosine deaminase (ADA) ratios differed significantly between patients with CHF/CRF, MPE, TBPE, empyema, and PPE. We discovered a simple method to differentiate pleural diseases based on the pleural LDH to ADA ratio and carcinoembryonic antigen (CEA). A pleural LDH to ADA ratio greater than 15.5 and a pleural CEA level of less than 5ng/mL is indicative of PPE or empyema rather than TBPE, MPE, or transudative pleural effusion (CRF, CHF). This method has a sensitivity of 62.0%, a specificity of 91.0%, and an area under the receiver operating characteristic curve of 0.765 (95% confidence interval [CI]: 0678-0.852, P<.001), odds ratio of 16.6 (95% CI: 7.28-37.8, P<.001), a positive likelihood ratio (LR) of 6.8, and a negative LR of 0.02.