Can pleural biopsy histology in combination with pleural fluid adenosine deaminase be used for diagnoses of pleural TB?

<b>Background:</b> Tuberculous pleural infection is the most common form of extrapulmonary TB, pleural fluid adenosine deaminase (pfADA) has been used to provide supportive evidence for a diagnosis of TB. Alternatively, reports suggest pleural histology has a sensitivity of 69-97% and can, therefore, be used as a biomarker for the diagnosis of pleural TB. <b>Aim:</b> To identify the utility of pleural biopsy histology and pfADA in the diagnosis of pleural TB. <b>Methods:</b> We conducted a retrospective case series collection of 106 patients diagnosed with pleural Tuberculosis at a tertiary pleural service from 2010 to 2019. All patients received treatment for TB as per UK national guidelines and adjusted for culture sensitivities. <b>Results:</b> 106 patients were identified, of which 12 were excluded due to insufficient data. 77 patients had a pleural biopsy performed, 50 had pfADA sent; 42 patients had pleural biopsy histology tested and a pfADA measurement. In 100% (42/42) the measured pfADA was ≥30 IU/l; of which 90% (38/42) had granulomatous inflammation on the histopathology biopsy specimen. Of these 40 patients had pfADA &gt;45 IU/l. Of patients with pfADA &gt; 45 IU/l, 65% (26/40) had necrotising granuloma, 25% (10/40) had non-necrotising granuloma, and 10% (4/40) did not have granulomas. Those that did not have granulomas were treated on pleural fluid culture and ADA with positive clinical history. <b>Conclusion:</b> Pleural biopsy histology demonstrating granulomatous inflammation in combination with pfADA &gt;45 IU/l is a useful biomarker for diagnosing pleural TB.