B. Stop further nontubercular diagnostic testing and continue antitubercular therapy
ADA is an enzyme in lymphocytes and myeloid cells that recycles toxic purine pathway metabolites, which are essential for DNA metabolism and cell viability.1,2 ADA levels are elevated in inflammatory effusions, including pleural, pericardial, and joint effusion, caused by bacterial infections, granulomatous inflammation (eg, tuberculosis, sarcoidosis), malignancy, and autoimmune diseases (eg, lupus, vasculitis).1,2 ADA is normally elevated in neutrophil-predominant effusions and is not a useful diagnostic test in the setting of neutrophil-predominant effusions.3 However, among lymphocyte-predominant effusions, levels of ADA are typically higher in those caused by tuberculosis (TB) than those caused by other conditions.1,2