Laboratory and radiological discrimination between tuberculous and malignant pleural effusions with high adenosine deaminase levels

Abstract

Background/aims: Pleural fluid adenosine deaminase (ADA) levels are useful in discriminating tuberculous pleural effusions (TPEs) from malignant pleural effusions (MPEs). However, some patients with MPE exhibit high-ADA levels, which may mimic TPEs. There is limited data regarding the differential diagnosis between high-ADA MPE and high-ADA TPE. This study aimed to identify the predictors for distinguishing high-ADA MPEs from high-ADA TPEs.

Methods: Patients with TPE and MPE with pleural fluid ADA levels ≥ 40 IU/L were included in this study. Clinical, laboratory, and radiological data were compared between the two groups. Independent predictors and their diagnostic performance for high-ADA MPEs were evaluated using multivariate logistic regression analysis and receiver operating characteristic curve.

Results: A total of 200 patients (high-ADA MPE, n = 30, and high-ADA TPE, n = 170) were retrospectively included. In the multivariate analysis, pleural fluid ADA, pleural fluid carcinoembryonic antigen (CEA), and pleural nodularity were independent discriminators between high-ADA MPE and high-ADA TPE groups. Using pleural ADA level of 40 to 56 IU/L (3 points), pleural CEA level ≥ 6 ng/mL (6 points), and presence of pleural nodularity (3 points) for predicting high-ADA MPEs, a sum score ≥ 6 points yielded a sensitivity of 90%, specificity of 96%, positive predictive value of 82%, negative predictive value of 98%, and area under the receiver operating characteristic curve of 0.965.

Conclusion: A scoring system using three parameters may be helpful in guiding the differential diagnosis between high-ADA MPEs and high-ADA TPEs.

Keywords: Adenosine deaminase; Carcinoembryonic antigen; Malignant pleural effusions; Pleural nodularity; Pleural tuberculosis.

Figure 1

Flowchart of the study population. MPE, malignant pleural effusion; TPE, tuberculous pleural effusion; ADA, adenosine deaminase; CT, computed tomography; CEA, carcinoembryonic antigen.

Figure 2

(A) Distribution of pleural fluid adenosine deaminase (ADA) levels in patients with high-ADA malignant pleural effusion (MPE) and high-ADA tuberculous pleural effusion (TPE). Black solid and red dotted lines indicate 56 and 40 IU/L, respectively. (B) Distribution of pleural fluid carcinoembryonic antigen (CEA) levels in patients with high-ADA MPE and high-ADA TPE. Black solid line indicates 6 ng/mL. (C) Proportion of pleural nodularity on chest computed tomography in patients with high-ADA MPE and high-ADA TPE.