Detection of TB by smear microscopy and GeneXpert MTB/RIF assay in non expectorating pulmonary TB suspects and pleural TB in high prevalent low income setting

Introduction Pakistan is 4 th among the 12 countries with 75% of 2.9 million missing TB cases. Not expectorating pulmonary TB cases are often missed. Gastric aspirate is obtained in these cases for AFB smear and culture. Diagnoses of extra pulmonary TB especially the pleural TB is difficult. GeneXpert MTB/RIF (Xpert) Assay has shown promising results in diagnosis of TB. The purpose of this study was to test the efficiency and reliability Xpert system for the detection of M. tuberculosis bacteria in gastric aspirate and pleural fluids Method Gastric aspirated were taken from all non expectorating TB suspects attending Ojha institute of chest diseases Karachi In 2013. Pleural tap was obtained from pleural TB suspects. Specimens were tested for Mycobacterium by smear microscopy and Xpert assay. Result Out of 521 specimens tested 110, 113 and 38 were gastric aspirate, pleural fluid and pleural pus. Among these 57(51.8%), 17(44.7%) and 64(90.1%) of gastric aspirate, pleural pus and pleural fluid tested respectively were new cases. Smear was positive in 65(59.1%), 16(42.1%) and 7(9.1%) of gastric aspirate, pleural pus and pleural fluid respectively. TB was detected in 66(60%), 21(55.3%) and 8(11.3%) of gastric aspirate, pleural pus and pleural fluid with Xpert respectively. Rifampacin(R) resistance was detected in 8 gastric aspirates and 1 pleural pus. Conclusion Xpert shows additional detection of 1%, and 2% by gastric aspirate and pleural fluid but 12% additional detection in pleural pus. R resistance was detected in 7.2% gastric aspirates and 2.6% pleural pus. Therefore Xpert should be more frequently used.