A70-44 Adeno--Not--Carcinoma--Adenosine Deaminase in Current Day Practice

Abstract Introduction The incidence of Tuberculosis (TB) in the United States of America is 2.9 cases per 100000 persons in 2023. Pleural TB accounts for 3.3% to 4% of all TB cases. We present a case of culture-negative pleural TB that ultimately led to the diagnosis of active pulmonary TB. Description of actual case report A 93-year-old male was initially hospitalized for acute hypoxic respiratory failure secondary to a large right pleural effusion. Pleural fluid analysis revealed an exudative effusion with a total nucleated cell count of 1,050/µL, showing 86% lymphocytic predominance. Cytology was negative for malignancy. Adenosine deaminase (ADA) levels were markedly elevated at 96 U/L (normal: 0-30), and the QuantiFERON-TB Gold test was positive. Sputum acid-fast bacilli (AFB) stains and cultures were negative. A chest tube was placed for complete drainage of the effusion. During pulmonary follow-up, a repeat chest CT demonstrated new infiltrates in the right middle and lower lobes. Given concern for active tuberculosis, the patient was referred to the state health department. Subsequent testing confirmed Mycobacterium tuberculosis by polymerase chain reaction (PCR). He was initiated on standard anti-tuberculous therapy consisting of isoniazid, rifampin, ethambutol, and pyrazinamide. Notably, in 2020, the patient had a right upper lobe cavitary lesion. Bronchoalveolar lavage (BAL) was negative for AFB on stain and culture. He was empirically treated with oral antibiotics for four weeks, after which a follow-up CT scan showed resolution of the cavitary lesion. Discussion of novelty and importance Tuberculosis is relatively rare in the United States, and pleural TB represents an even smaller subset of cases. The diagnosis of pleural TB by routine microbiological tests is challenging because of its paucibacillary nature. One study finds the sensitivity of TB PCR to be 1.4% and AFB culture to be 5.6% in pleural fluid. Other findings, such as lymphocytic effusion and elevated adenosine deaminase levels, can aid in the diagnosis of pleural tuberculosis. Elevated ADA is 93 % sensitive and 92 % specific for TB pleural effusions. Early initiation of treatment, along with drainage of the effusion, reduces the likelihood of residual pleural thickening and functional impairment. Conclusion In patients presenting with pleural effusion characterized by lymphocytic predominance, a high index of suspicion for TB should be maintained—especially in the absence of an alternative diagnosis. ADA levels can be a valuable diagnostic tool in such cases, particularly when sputum acid-fast bacilli smears and cultures are initially negative. This abstract is funded by: None