Diagnostic value of the cancer ratio in pleural effusion – a retrospective study

Abstract

<b>Introduction:</b> The cancer ratio (CR), which is defined as serum lactate dehydrogenase to pleural fluid adenosine deaminase (sLDH/pADA) ratio, has been identified as a potential diagnostic parameter in malignant pleural effusion (MPE). Nonetheless, the available studies were based on exudates as control, whilst transudates were usually not included. <b>Objective:</b> This study aimed to assess the diagnostic value of CR in the diagnosis of MPE when compared with benign pleural effusions (BPE), both exudates and transudates. <b>Methods:</b> Retrospective analysis of 295 patients with pleural effusion (PE) between 2014 and 2021, including clinical and laboratory data. The diagnostic performance of CR&nbsp;was analyzed using the receiver operating characteristic (ROC) curves and the area under the curve (AUC) as a measure of accuracy. <b>Results:</b> Of the 295 PE studied, 51 were transudates. The remaining exudates included 121 MPE and 134 BPE, of which 15 were misclassifications (PE from heart failure after diuretic therapy). Significantly higher CR levels were observed in MPE than in exudative BPE (p&lt;0.001). When comparing MPE to exudative BPE (without misclassifications), the CR ratio at a cut-off value of 20 showed an AUC 0.91 with a sensitivity of 84% and a specificity of 92%. The inclusion of misclassified exudative BPE and transudates led to a reduction in diagnostic accuracy (AUC 0.87/0.75, sensitivity 84%/84% and specificity 87%/69%, respectively). <b>Conclusion:</b> The cut-off level for CR of &gt;20 is highly predictive of malignancy in patients with exudative PE, without requiring additional testing. In order to maximize its diagnostic accuracy it is important to always classify transudates and exudates before using the CR.