Ultrasound elastography: a novel tool for the differential diagnosis of pleural effusion

Introduction: Traditional thoracic ultrasound (TUS) is often the initial tool used to help diagnose malignant pleural effusion (MPE). Ultrasound elastography, a relatively new technique, has been used to differentiate malignant disease from benign disease by evaluating tissue "stiffness". However, no studies evaluating the efficacy of ultrasound elastography for diagnosing MPE are available. We assessed the value of ultrasound elsatography for diagnosing MPE prospectively. Methods: All 244 enrolled patients were divided into a development set and a validation set in chronological order. The cut-off elasticity index was established using a receiver operating characteristic curve constructed from the continuous data of the patients in the development set. The diagnostic performance of ultrasound elastography was compared with that of TUS in the validation set. Results: In the development set, the mean elasticity index (47.25 kPa) was the optimal cut-off. In the validation set, pleural ultrasound elastography had a sensitivity of 83.64%, a specificity of 90.67%, a positive predictive value of 86.79%, a negative predictive value of 88.31%, a positive likelihood ratio of 8.96 and a negative likelihood ratio of 0.18 for diagnosing MPE. The sensitivity of ultrasound elastography was significantly higher (p=0.006) than that of TUS (60%). Conclusion: Pleural ultrasound elastography is a better technique than TUS for differentiating MPE from benign pleural disease.