International Journal of Advances in Medicine | February 2022 | Vol 9 | Issue 2 Page 102 International Journal of Advances in Medicine Nishanth PS et al. Int J Adv Med. 2022 Feb;9(2):102-106 http://www.ijmedicine.com pISSN 2349-3925 | eISSN 2349-3933 Original Research Article Diagnostic utility of cancer ratio in differentiating malignant from non- malignant pleural effusions in a tertiary care centre in central Kerala P. S. Nishanth, Thomas Vadakkan Devassy*, Tessa Jose INTRODUCTION Exudative effusion is commonly seen in three conditions namely cancer, tuberculosis and parapneumonic effusion. Malignant pleural effusion (MPE) is associated with unfavorable prognosis and is a common clinical condition observed in patients suffering from malignant diseases, such as primary thoracic cancer, pleural mesothelioma, metastatic cancer, etc. 1-3 It is associated with unfavorable prognosis and a median survival time of 3-12 months. 4,5 Assessment and comparison of serum Lactate dehydrogenase (LDH) and protein with the pleural fluid LDH and protein (based on Light‘s criteria) is the first step determine the exudative or transudative nature of the effusion associated with the management of pleural effusion. 6-9 Once an exudative effusion is identified, further work-up entails its analysis for cell count, glucose, pH, Adenosine deaminase (ADA), cytology and TB culture. If the biochemical results are inconclusive then invasive techniques closed pleural biopsy or thoracoscopy is done to confirm the diagnosis. Low diagnostic yield of pleural fluid cytology (∼60%), and the invasive nature of closed or thoracoscopic pleural biopsy are a significant limitation in detecting MPE. 10-12 Often the low levels of ADA are used as a surrogate indicator of malignant effusion while waiting for the cytology result. Among the routinely performed tests for investigating pleural effusion, serum LDH, pleural ADA and pleural ABSTRACT Background: Malignant pleural effusion (MPE) is a common clinical condition observed in patients suffering from malignant diseases. None of the tumour markers have both high sensitivity and specificity. A retrospective study on patients with pleural effusion was done to evaluate the diagnostic accuracy of Cancer ratio (CR) in diagnosing MPE. Methods: A retrospective analysis of patients with undiagnosed exudative pleural effusion was done. Results of serum Lactate dehydrogenase (LDH), pleural fluid Adenosine deaminase (ADA), pleural fluid analysis such as cytology and histopathology reports of pleural biopsy were analyzed. Serum LDH: pleural fluid ADA ratio (CR) was calculated and compared with histopathology report. Data were analyzed statistically. Results: A total of 102 patients were enrolled in the study (56 males and 46 females). The sensitivity and specificity of CR at the cut off level of >20 were 57.14% and 75.47% respectively. The positive predictive value was 68.29% and the negative predictive value was 65.57%. CR>20 (p<0.001) is statistically significant in predicting malignancy in undiagnosed exudative pleural effusions. Conclusions: CR has a high sensitivity and specificity and is a novel tool in differentiating malignant from nonmalignant pleural effusions. Patients with unconfirmed diagnosis but higher CR will identify the need for early biopsy, follow-up and frequent or repeat chest imaging to assess the progression. Keywords: Cancer ratio, Malignant pleural effusion, Tubercular pleural effusion, Parapneumonic effusion Department of Pulmonary Medicine, Amala Institute of Medical Sciences, Thrissur, Kerala, India Received: 04 January 2022 Accepted: 19 January 2022 *Correspondence: Dr. Thomas Vadakkan Devassy, E-mail: drvdthomas@gmail.com Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. DOI: https://dx.doi.org/10.18203/2349-3933.ijam20220116