Diagnostic utility of pleural fluid carcinoembryonic antigen in patients with exudative pleural effusion

Pleural effusion (PE) is presenting symptoms of many different diseases and is often a diagnostic challenge. Negative cytology in the malignant PE requires more complicated diagnostic procedures, such as closed pleural biopsy or thoracoscopic pleural biopsy. Not all the patients will be fit for such invasive procedures due to high risk. Tumor markers seem to be a promising alternative and have been proposed to aid in the differentiation of the PE etiology.

The objective of the study was to evaluate the diagnostic value of pleural fluid carcinoembryonic antigen (CEA) in differentiation between malignant and nonmalignant PEs and to compare adenosine deaminase (ADA) levels with respect to malignant and nonmalignant PE.

It was a prospective observational study. Patients who presented with undiagnosed exudative PE during the time period 2016-2018 were studied. Pleural fluid was subjected to all routine investigations such as sugar, protein, lactate dehydrogenase, ADA, and CEA.

A total of 100 patients were included in the study. Fifty-one patients had malignancy. Univariate analysis showed that smoker, previous history of cancer, ADA <20, and CEA of >2.15 were variables associated with malignancy. Multivariate analysis showed pleural fluid CEA >2.15 as only independent risk factor associated with malignancy. The sensitivity of 91.5% and 65% and specificity of 92.5% and 81.4%, respectively, were found for CEA 2.15 ng/dl and ADA <16.5 U/L as plotted from receiver operating characteristic curve. The combined CEA and ADA (2.39 ng/ml and 16.5 U/L) values in pleural fluid had higher sensitivity of 100%.

Our study demonstrated that pleural fluid CEA levels have a sensitivity of 93.5% and specificity of 73% in diagnosing of malignant PE. ADA levels lesser than 16.5 U/L were seen in patients with malignant PE, but less sensitive and specific compared to CEA. Combined ADA and CEA levels had higher sensitivity than CEA alone.