Cancer ratio and other new parameters for differentiation between malignant and nonmalignant pleural effusions

Introduction In contrast to tuberculous pleurisy (TP), no accurate and commonly accepted biochemical marker of malignant pleural effusion (MPE) has been established. Objectives We aimed to evaluate the ability of a previously reported cancer ratio (CR) to discriminate between MPEs and non-MPEs; to test whether age may have additional value in differentiating MPEs from non-MPEs; and if so, to combine lactate dehydrogenase (LDH) and age with other TP biomarkers in search of an index useful in the identification of MPEs. Patients and methods A retrospective analysis of data from 140 patients with malignant (n = 74), tuberculous (n = 37), and parapneumonic (n = 29) pleural effusions was performed. The diagnostic performance of a test to discriminate between MPEs and non-MPEs was evaluated using the receiver operating characteristic curve analysis. Results Three ratios showed the largest area under the curve (AUC): serum LDH to pleural fluid soluble Fas ligand, age to pleural fluid adenosine deaminase (ADA), and serum LDH to pleural fluid interleukin 18; moreover, the ratios were characterized by high sensitivity (95%, 93.2%, and 92.9%, respectively) and fair specificity (64.8%, 71.2%, and 58.5%, respectively) for differentiating MPEs from non-MPEs. The AUC for CR was lower and showed a sensitivity of 94.6% and a specificity of 68.2%. Conclusions Our study showed a lower specificity of the CR for discriminating between MPEs and non-MPEs than previously reported. We demonstrated that the combinations of serum LDH with other pleural fluid biomarkers of TP have a similar diagnostic performance. We also found that age might be an important factor differentiating between MPEs and non-MPEs and proposed a new age to pleural fluid ADA ratio which has a discriminative potential similar to that of the CR.