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Open Access Highly Accessed Research article

Factors affecting pleural fluid adenosine deaminase level and the implication on the diagnosis of tuberculous pleural effusion: a retrospective cohort study

Tunn Ren Tay* and Augustine Tee

Author Affiliations

Department of Respiratory Medicine, Changi General Hospital, 2 Simei Street 3, Singapore 529889, Singapore

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BMC Infectious Diseases 2013, 13:546  doi:10.1186/1471-2334-13-546

Published: 16 November 2013

Abstract

Background

Adenosine deaminase (ADA) is useful in the diagnosis of tuberculous pleural effusion (TPE). This study aims to determine the factors affecting pleural fluid ADA levels and to establish the optimal ADA levels for diagnosis of TPE for different age groups.

Methods

This was a retrospective study from January 2007 to October 2011. One hundred and sixty patients who had pleural fluid ADA performed for investigation of pleural effusion were analyzed. Variables examined included demographics, pleural fluid characteristics and peripheral blood counts. The ADA cut-offs according to age were selected using the receiver operating characteristic (ROC) curve.

Results

The mean pleural fluid ADA was significantly higher in the TPE group (100 ± 35 IU/L) compared to non TPE patients (30 ± 37 IU/L). There was significant correlation between pleural fluid ADA and age, pleural fluid protein, LDH, and fluid absolute lymphocyte count. The strongest correlation was seen with age (r = −0.621). For patients ≤ 55 years old the ROC for ADA had area under curve (AUC) of 0.887. A pleural fluid ADA of 72 IU/L had sensitivity of 95.1%, specificity of 87.5%, positive predictive value (PPV) of 95.1% and negative predictive value (NPV) of 87.5% for the diagnosis of TPE. For patients > 55 years old the AUC is 0.959. ADA of 26 IU/L had a sensitivity of 94.7%, specificity of 80.4%, PPV of 62% and NPV of 97.8%.

Conclusions

There is a significant negative correlation between pleural fluid ADA and age. For older patients, a lower ADA cut-off should be used to exclude TPE.

Keywords:
Adenosine deaminase; Tuberculosis; Pleural effusion; Biological markers