Optimizing tuberculosis diagnosis: A comparative study of mycobacterial growth indicator tube (MGIT) versus GeneXpert for smear-negative pulmonary and extra-pulmonary cases

• Author Details:   
• Kayalvili Kaliyamoorthy Sabha ^*
• Nivedhitha Elangovan
• Arulselvan Subramanian
• Selvi Elangovan

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Background: Tuberculosis being a major global health issue. Accurate diagnosis of tuberculosis and drug resistance detection are the key components to manage Tuberculosis. Diagnosis in smear-negative pulmonary specimens & Extra-pulmonary specimens constitutes a major challenge. We studied the performance of the micro Mycobacterial Growth indicator tube instrument (MGIT) & GeneXpert the Nucleic Acid Amplification Testing (NAAT) assay for the timely diagnosis of tuberculosis in smear-negative pulmonary and extra-pulmonary specimens from the tuberculosis suspected patients.
Materials and Methods: This study was done at the Department of Microbiology, a tertiary care centre, Stanley medical college and Hospital. Pulmonary specimens (only smear-negative) and extra-pulmonary specimens (both smear-positive and negative) were collected from the tuberculosis suspects and tested for MGIT culture & GeneXpert.
Results: A total of 100 specimens were included among them 49% were pulmonary specimens (smear-negative) and 51% were extrapulmonary specimens (both smear positive and negative). In total Mycobacterial Growth Indicator tube detected 17 % and GeneXpert detected 26%. Out of 49 smear-negative pulmonary specimens MGIT detected 16% (8/49) whereas GeneXpert detected 10/51(20%). Out of 51 extra pulmonary specimens MGIT detected 17.6% (9/51) and GeneXpert detected 31 % (16/51). There was 90% correlation between MGIT & GeneXpert with respect to Mycobacterium tuberculosis complex identification.
Conclusion: This study supports that the concurrent use of MGIT culture with GeneXpert could increase the detection rate of tuberculosis within a shorter Turn around time (TAT), especially in paucibacillary specimens.

Keywords: microMGIT – Mycobacterial growth indicator tube, GeneXpert, NAAT - Nucleic acid amplification technique, TAT - Turn around time.