Utility of GeneXpert MTB/Rif for detection of drug resistance in tuberculous pleural effusion(TPE) in high endemic areas

Abstract

<b>Background:</b> TPE is a paucibacillary disease and GeneXpert MTB/Rif has a modest sensitivity of 40-60% in diagnosis of TPE. It provides additional information for Rifampicin resistance(RR) which is used as a surrogate marker for multidrug resistant(MDR-TB) tuberculosis and this is particularly useful in high endemic MDR TB areas. However,in the presence of a low tuberculous bacillary load,although GeneXpert MTB/Rif can detect presence of Mycobacterium Tuberculosis(MTB),RR may be undiagnosed and is often reported as ‘Indeterminate’. <b>Aim:</b> To assess&nbsp;RR patterns in patients with TPE with a positive GeneXpert MTB/Rif on their pleural sample. <b>Methods:</b> Retrospective review of pleural fluid/pleural tissue samples sent at PD Hinduja National Hospital, Mumbai for Genexpert MTB/Rif from Jan2019–Dec2021 was carried out. <b>Results:</b> GeneXpert MTB/Rif detected MTB in 284 pleural samples. Of these,249 were pleural fluid and 35 were pleural tissue samples. Overall RR patterns were available in 58%(165/284) specimens,while the remaining 42%(119/284) samples had an indeterminate resistance pattern. Overall Rif Susceptibility and Rif resistance were seen in 45%(128/284) and 13%(37/284) samples respectively. Indeterminate results were seen in 55%(136/249) and 17%(6/35) of pleural fluid and tissue specimens respectively. MTB was detected as ‘trace’ in 97%(116/119) of the indeterminate samples. <b>Conclusion:</b> In pleural samples where GeneXpert MTB/Rif is positive,pleural tissue is more likely&nbsp;to provide a resistance pattern as compared to pleural fluid(p value 0.001). In high&nbsp;MDR-TB endemic areas,attempts should be made to send pleural tissue for GeneXpert MTB/Rif in addition to pleural fluid.