Evaluation of Pleural Fluid Adenosine Deaminase Activity and Its Biochemical and Physiological Significance in the Diagnosis of Tuberculous Pleural Effusion among Symptomatic Patients

Abstract

Background: One of the frequent extrapulmonary TB manifestation is tuberculosis Pleural effusion, which is often paucibacillary, making it a diagnostic challenge. Traditional techniques like pleur Tib and microbiological testing can be invasive, time consuming or only yield results in some cases. It has been suggested that the activity of adenosine deaminase in the pleural fluid can be used as a useful supportive test to support the early diagnosis of tuberculous pleural effusion.

Objective: To determine the diagnostic accuracy of adenosine deaminase activity in the diagnosis of tuberculous pleural effusion among symptomatic patients.

Methods: This is a cross sectional study of diagnostic accuracy conducted from 25th March 2025 to 25th June 2025 in Department of Medicine, Women Medical College, Abbottabad. The number of patients was 100, and the sampling method used was non-probability consecutive sampling, which were patients with symptoms of pleural effusion ranging in age from 16 to 75 years. Thoracentesis was performed to obtain the pleural fluid for ADA measurement. Tuberculous Pleural Effusion was considered to be positive when ADA level was >55.8 U/L. Biopsy of the pleura was done and was the gold standard. The data were analyzed by SPSS version 25. A 2×2 table was used to calculate sensitivity, specificity, positive and negative predictive value, and diagnostic accuracy.

Results: The mean age of the patients was 42.6 ± 14.8 years, and 58.0% were male. Pleural biopsy confirmed tuberculous pleural effusion in 35.0% of patients, while ADA was positive in 39.0%. When ADA findings were compared with pleural biopsy, 31 cases were true positive, 57 were true negative, 8 were false positive, and 4 were false negative. The sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy of ADA were 88.6%, 87.7%, 79.5%, 93.4%, and 88.0%, respectively. Patients with biopsy-confirmed tuberculous pleural effusion had significantly higher pleural fluid lymphocyte percentages and lymphocyte-to-neutrophil ratios than biopsy-negative patients. Lymphocyte-predominant pleural effusion was present in 91.4% of biopsy-positive patients compared with 60.0% of biopsy-negative patients (p = 0.001). A significant association was observed between ADA results and pleural biopsy findings (p < 0.001).

Conclusion: Pleural fluid adenosine deaminase activity showed good diagnostic accuracy for tuberculous pleural effusion in symptomatic patients. ADA testing is a rapid, simple, and less invasive supportive diagnostic tool, especially in settings where tuberculosis is common. However, ADA should be interpreted along with clinical findings, radiological assessment, and confirmatory investigations where required.