Role of line probe assay in detection of extra-pulmonary tuberculosis: Experience from a tertiary care hospital in western Maharashtra.

BACKGROUND: Diagnosis of extra pulmonary tuberculosis (EPTB) is challenging due to its atypical clinical presentation and frequently results in a delay or deprivation of treatment. Apart from rapid case detection, early determination of MDR status is imperative in such situations. The commercially available Geno Type MTBDRplus assay version 2.0 (Hain Lifescience, Nehren, Germany) detects both the presence of Mycobacterium tuberculosis (MTB) complex as well as the presence of INH and Rifampcin resistance. We aim to evaluate the role of this test in diagnosis and detection of resistance by comparing its performance against gold standard i.e. culture and against the composite reference standards (CRS) in the diagnosis of EPTB. MATERIAL AND METHODS: The data of 130 EPTB samples processed form January 2014 till May 2017 at Poona Hospital and Research centre were selected for the study. All the samples were processed for Ziehl-Neelsen stain, Geno Type MTBDRplus assay (LPA) and liquid automated culture (BacT/Alert) simultaneously. Geno Type MTBDRplus assay (LPA) was performed directly on the samples. The 24 samples giving positive results on LPA and grown M. tuberculosis on culture were subjected to anti mycobacterial susceptibility testing for 1st line anti-tubercular drugs by BACTEC MGIT 320 system. RESULTS: Out of 130 samples, 7 samples grew atypical mycobacterium and all the 7 samples turned negative on Line Probe Assay. Direct LPA on processed samples yielded 48/130 (36.9%) positivity. Geno Type MTBDRplus assay was positive for M. tuberculosis in (72.09%) 31/43 culture positive cases and (21%) 17/80 of culture negative cases. Geno Type MTBDRplus assay sensitivity and specificity results were assessed in comparison to CRS made up of culture results and clinical, radiological and histological findings. The overall sensitivity of Geno Type MTBDRplus assay was 45.19% (47/104) and specificity was 94.73 (18/19). Out of 24 samples which were compared for results between LPA and culture, Geno Type MTBDRplus assay accurately identified 3 of 3 of Rifampcin resistant strains and 20 of 21 Rifampcin sensitive strains. Geno Type MTBDRplus assay identified 4 of 4 INH resistant strains and 19 of 20 INH sensitive strains and MDR was obtained for 3 of 3 strains. CONCLUSIONS: Geno Type MTBDRplus assay can give early diagnosis and sensitivity for both INH and Rifampcin in extra pulmonary samples. More number of studies is further required to establish Geno Type MTBDRplus assay as an important tool for obtaining diagnosis and resistance to first line drugs in extra pulmonary samples.

Incidence of tuberculosis among HIV infected individuals on long term antiretroviral therapy in private healthcare sector in Pune, Western India.

BACKGROUND: Despite rapid scale up of antiretroviral therapy (ART), Tuberculosis (TB) remains the commonest opportunistic infection and cause of death among HIV infected individuals in resource limited settings like India. Incidence of TB in individuals on ART in private healthcare sector in India is infrequently studied. METHODS: This retrospective cohort study conducted between 1st March 2009 and 1st March 2017 aimed to evaluate rate of incident TB in individuals initiated on ART at 3 private sector ART clinics in Pune, India. Individuals more than 12 years of age with ART duration of atleast 6 months were included. Patients were classified as having prevalent TB if they had a TB episode within the year prior to ART initiation or if they developed TB within 6 months of starting ART. Individuals who were diagnosed with TB after 6 months of starting ART were classified as incident TB cases. A recurrent episode of TB after treatment completion or cure of prevalent TB was also regarded as incident TB. Patients were classified as definitive TB if Mycobacterium tuberculosis was grown in culture from a biological sample or a positive rapid molecular test. Patients were classified as probable TB if there was radiologic evidence of TB in absence of confirmatory culture or PCR. RESULTS: 1904 patients with a median duration of follow up on ART of 57 (IQR = 32.0, 84.0) months were included. Of these, 182 developed incident TB (22% definitive TB, 38% recurrent cases). TB incidence at 6-12 months, 13-24 months, 25-60 months and > 60 months of ART was 24.32, 5.46, 2.54 and 0.75 cases per 100 person years respectively. Current time updated CD4 count < 500 cells/mm3 (p < 0.0001), virologic failure on ART (adjusted Hazard Ratio (aHR): 3.05 (95% CI: 2.094, 4.454), p < 0.0001) and receipt of ART without IPT (aHR: 8.24 (95% CI, 3.358, 20.204), p < 0.0001) were associated with higher risk of incident TB. CONCLUSION: Starting ART early in treatment naïve individuals, prompt detection of virologic failure on ART and providing IPT along with ART will be useful in reducing incident TB. Efforts from private sector are crucial in achieving Sustainable Development Goals set by Government of India and attaining the vision of a TB free India.