Pleural ultrasonic elastography in the diagnosis of malignant pleural effusion

Background: Thoracic ultrasound (TUS) is useful in diagnosis of malignant pleural effusion (MPE). While ultrasonic elastography (UE) has been shown to be valuable in the diagnosis of thyroid and breast cancers, its usage in the diagnosis of MPE has not been assessed. Here a study was performed to assess the accuracy of UE of pleura in differentiating MPE from benign pleural diseases. Methods: Sixty one consecutive patients with suspected MPE were undertaken TUS and UE (ShearWave™ Elastography, Supersonic Imagine, France). Receiver operating characteristic curve of elasticity value (EV) was built to confirm the cut-off of diagnosis of MPE. Definitive diagnosis of MPE was based on histocytology, and benign pleural effusion was based on negative histocytology and follow-up over 12 months. The UE diagnosis was compared with definitive diagnosis. Results: Malignant diagnoses included lung cancer (19/26), malignant mesothelioma (3/26) and breast cancer (1/26). Benign diagnoses included tuberculous pleuritic (23/35), parapneumonic pleural effusion (5/35), bacterial empyema (2/35), cardiac failure (2/35) and rheumatoid arthritis(1/35). When 48.7 kilo-Pascals (kPa) was set as the cut-off of mean EV or 60.05 kPa was set as the cut-off of maximum EV (sensitivity 80.8%, specificity 80%, positive predictive value 75%, negative predictive value 84.8%; Area under curve was 0.780 and 0.792 separately). The tuberculous pleuritis and empyema was the main reason for false positivity of UE in diagnosis of MPE. Conclusion: pleural ultrasonic elastography is a valuable and effective technique in differentiating MPE from benign pleural effusion and may become an important adjunct in diagnostic methods.