Thoracic Ultrasonography May Not Reliably Diagnose Transudative Pleural Effusion

Thoracic ultrasonography may not be a reliable method for distinguishing transudative pleural effusions from exudative pleural effusions, according to study results published in CHEST.

Researchers retrospectively identified 285 patients who underwent a thoracic ultrasonography and a diagnostic thoracentesis with a pleural fluid analysis. A total of 300 consecutive pleural effusions were included in the analysis. The images of the pleural effusions were classified as anechoic, complex non-septated, complex septated, or complex homogenous. Diagnostic performance of the thoracic ultrasonography findings for predicting transudative vs exudative pleural effusions was assessed.

In 76% (n=229) of cases, the pleural effusions were classified as exudative. The thoracic ultrasonography demonstrated anechoic effusions in 40% (n=122) of cases, whereas 60% (n=178) of cases were identified as complex effusions. Thoracic ultrasonography images that demonstrated an anechoic appearance correlated with 56% (n=68) of cases being identified as exudative effusions vs 44% (n=54) of cases being identified as transudative effusions 54/122 (44%).

A thoracic ultrasonography that showed a complex-appearing effusion featured a positive predictive value of 90% in terms of its ability to detect exudative effusion. Despite this finding, none of the 4 characteristics associated with thoracic ultrasonography showed high levels of specificity of a pleural diagnosis.

Limitations of the study included being conducted in a single institution as well as the lack of standardization for thoracic ultrasonography images. Additionally, some of the investigators treated the cases in this study, which may have introduced recall bias.

The researchers added that while “the [thoracic ultrasonography] finding of a complex appearing pleural effusion strongly suggests an exudate, thoracentesis is still needed to establish a diagnosis.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Shkolnik B, Judson MA, Austin A, et al. Diagnostic accuracy of thoracic ultrasonography to differentiate transudative from exudative pleural effusion [published online March 17, 2020]. CHEST. doi:10.1016/j.chest.2020.02.051