Eiman Mokaddas
Kuwait University, Kuwait
Title: Evaluation of the performance of 2 DNA-based methods for the detection of extra-pulmonary tuberculosis in comparison with the conventional culture technique.
Biography
Biography: Eiman Mokaddas
Abstract
Introduction:
Diagnosing extra-pulmonary tuberculosis continues to be a challenge for both infectious disease specialists and microbiologists.
Objectives:
This prospective study was done to evaluate the performance of 2 DNA-based methods for the detection of extra-pulmonary tuberculosis in comparison with conventional culture technique.
Methods:
All extra-pulmonary specimens received by the Kuwait National Tuberculosis Reference from October 2011 till August 2013 were included in the study. Smears were stained by Zeil Nelson ( Merck, Germany) followed by inoculation of the specimens into Gene Xpert MTB/RIF assay ( Cephieid, USA) , Prob Tec ET PCR(Becton Dickinson) and MGIT 960( Becton Dickinson). Urine was inoculated into Lowenstein Jonson media ( MAST).
Results:
A total of 1674 extra-pulmonary specimens ( pleural fluid 553, ascetic fluid 194, cerebrospinal fluid ( CSF) 85, Urine 67, other sterile body fluids 153, Fine needle aspirates ( FNA) 301, pus 181, tissue 102, swabs 27 and stool 11) were evaluated. Out of 155 extra-pulmonary specimens that grew Mycobacterium tuberculosis by culture, 143 were positive by GeneXpert compared to 128 by ProbTec with a sensitivity of 92% and 83%, respectively. Out of 1517 specimens which did not grow by culture,52 were detected by GeneXpertwhile 46 were detected by ProbTec with specificity of 96.5 and 96.9%, respectively. All the 4 Smear- negative CSF samples which grew M.Tuberculosis were positive by GeneXpert with a sensitivity of 100% compared to only 2 detected by ProbTec with a sensitivity of 50%. Additionally all CSF specimens that did not grew by culture were negative by both the molecular methods showing 100% specificity. Of the 3 smear positive urine specimens that grew by culture all were positive and of the 64 samples that did not grew by culture all were negativeby both the molecular methods with a sensitivity and specificity of 100%. For other sterile body fluids the sensitivity and specificity of both the methods were 68% and 99% , respectively. Finally, for FNA, pus and tissue , the sensitivity of GeneXpert was 97% compared to 86% for ProbTec.
Conclusion:
DNA-Based technology looks promising for the rapid diagnosis of extr-pulmonary Tuberculosis with an over all better performance of GeneXpert over PropTec.