Study of Differentiating Pleural Effusion as Transudative and Exudative Using Computed Tomography Scan and Thoracocentesis: A Cross-sectional Study in Central India

Aims and background: When there is excessive accumulation of fluid in pleural cavity, it is known as pleural effusion and classified as transudative or exudative on the basis of etiology. Distinguishing between them is critical for diagnosis and treatment. Light's criteria, an invasive method, remains the standard for classification. The purpose of this study is to ascertain how well computed tomography (CT) attenuation values distinguish between transudative and exudative pleural effusions. Materials and methods: Over the course of 18 months, a cross-sectional study was carried out in the Department of Pulmonary Medicine, SAMC & PG Institute, Indore. A total of 100 patients with pleural effusion detected on CT scan were recruited based on inclusion criteria. Patients having prior chest tube placement, poor image quality, or sampling not done in the first week were excluded. CT scans were performed using a 64-slice multidetector CT (MDCT) scanner, and attenuation values [Hounsfield units (HUs)] were recorded. Pleural fluid was analyzed based on Light's criteria for classification into transudate and exudate. SPSS (Statistical Package for Social Sciences) software (version 2.0) was used for statistical analysis and p-value < 0.05 was considered as significant. Results: Out of 100 patients, 57% had exudative and 43% had transudative effusions. The mean CT attenuation value for exudative effusions was 33.29 ± 12.23 HU, while for transudative effusions, it was 17.90 ± 8.26 HU (p < 0.01). A 22 HU was the optimal cutoff value to distinguish transudate from exudate as accuracy at this level was 79%, sensitivity 74.42%, and specificity 82.46%. The area under the receiver operating characteristic (ROC) curve was 0.729, which indicated fair discriminative ability. Conclusion and clinical significance: CT attenuation values provide a noninvasive method to differentiate pleural effusions with a reasonable accuracy. A cutoff value of 22 HU effectively classifies pleural effusions, potentially decreasing the chance for invasive diagnostic procedures such as thoracocentesis. Further studies having large sample size with advanced imaging techniques are warranted to enhance diagnostic precision.