Application of Adenosine Deaminase and γ-Interferon Release Assay in Pleural Fluid for the Diagnosis of Tuberculous Pleural Effusion in Patients Over 40 Years Old

Abstract

Background

In patients with tuberculous pleural effusion (TPE) of various ages, the diagnostic accuracy of pleural biomarkers varies, and there are insufficient studies specifically in different age groups. Therefore, we investigated the adenosine deaminase cut-off value and its combination with the gamma interferon release assay for the diagnosis of TPE among patients aged ≥40 years.

Methods

A retrospective analysis of 198 patients who underwent medical thoracoscopy and were admitted to the hospital between 2015 and 2020 with exudative pleural effusion and either fever, night sweats, fatigue, cough, or other clinical manifestations was performed. The medical thoracoscopy, ADA, and T-SPOT results were analysed in the pleural fluid. The patients were divided into groups based on age: 18–39, 40–59, and 60–87.

Results

The best cut-off values of ADA were 29.5, 31.5 and 19.5 U/L, respectively, for the aged 18–39, aged 40–87 and aged 60–87 groups. The accuracy of 31.5 U/L was higher than 40 U/L for aged ≥40 years (86 vs 83%). The ADA diagnostic accuracy was higher than that of people under 40 years (83 vs 77%) when cut-off value of ADA was 40 U/L, but the IGRA accuracy was lower than that of people under 40 (87 vs 91%). The sensitivity of ADA or IGRA detection in patients over 40 years was 99%, and the specificity was 78%. The ADA specificity combined with IGRA for TPE was the highest (100%) in the ≥40 age group, and the sensitivity was 69%.

Conclusion

Our study revealed the best cut-off values of ADA for TBE in different age groups. Combining ADA and IGRA in pleural fluid improves the detection rate of TPE in patients over 40 years of age with exudative pleural effusion. ADA combined with IGRA increases specificity, and ADA or IGRA increases sensitivity substantially.

Keywords:

• adenosine deaminase
• interferon gamma releasing assays
• aged
• diagnosis
• pleural effusion
• tuberculosis

Abbreviations

TPE, tuberculous pleural effusion; ADA, Adenosine deaminase; IGRA, interferon gamma release test; PF, pleural fluid; SFCs, Spot-forming cells; MTB, Mycobacterium tuberculosis; SPSS, Statistical package for social sciences; CI, Confidence interval; Acc, accuracy; LR+, positive likelihood ratio; LR−, negative likelihood ratio; PPV, positive predictive value; NPV, negative predictive value.

Data Sharing Statement

The data will be available on a reasonable request from the corresponding author.

Ethics Approval

All procedures performed in our study were in accordance with the ethical standards of the Medical Ethics Committee of Guangyuan Central Hospital and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. As the study design was retrospective, we used the currently existing samples collected during routine medical care and did not pose any additional risks to the patients. Thus, the informed consent was waived by Medical Ethics Committee of Guangyuan Central Hospital.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

This work was supported by the key R&D projects of the Science and Technology Bureau of Guangyuan City, Sichuan Province [20ZDYF0007].