Validation of an indigenous assay for rapid molecular detection of rifampicin resistance in presumptive multidrug-resistant pulmonary tuberculosis patients
NS Gomathi1, Manjula Singh2, VP Myneedu3, DS Chauhan4, Srikanth Tripathy5, Rohit Sarin6, Anant Mohan7, Anuj Bhatnagar8, Jiten Singh Khangembam9, T Kannan10, MV V. Rao9, Jyoti Logani11, Bindu Dey11, RR Gangakhedkar2, Soumya Swaminathan12, Urvashi B Singh13
1 Department of Bacteriology, Epidemiology Unit, Chennai, Tamil Nadu, India
2 Division of Epidemiology & Communicable Diseases, Indian Council of Medical Research, New Delhi, India
3 Department of Microbiology, National Institute of Tuberculosis & Other Respiratory Diseases, New Delhi, India
4 Department of Microbiology & Molecular Biology, ICMR-National JALMA Institute for Leprosy & Other Mycobacterial Diseases, Agra, Uttar Pradesh, India
5 ICMR-National Institute of Research in Tuberculosis, Chennai, Tamil Nadu, India
6 National Institute of Tuberculosis & Other Respiratory Diseases, New Delhi, India
7 Department of Pulmonary Medicine & Sleep Disorders, All India Institute of Medical Sciences, New Delhi, India
8 Department of Chest & TB, Rajan Babu Institute of Pulmonary Medicine and Tuberculosis, New Delhi, India
9 ICMR-National Institute of Medical Statistics, New Delhi, India
10 Statistics Section, Epidemiology Unit, ICMR-National Institute of Research in Tuberculosis, Chennai, Tamil Nadu, India
11 Department of Biotechnology, Ministry of Science & Technology, New Delhi, India
12 World Health Organization, Geneva, Switzerland
13 Department of Microbiology, All India Institute of Medical Sciences, New Delhi, India
Urvashi B Singh
Department of Microbiology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110 029
Source of Support: None, Conflict of Interest: None
Background & objectives: There is a need for an affordable, easy, high-sensitivity test usable at the peripheral health facility for diagnosis of drug-resistant (DR) tuberculosis (TB) to interrupt disease transmission. Nucleic acid amplification tests (NAATs) for early detection of DR-TB are ideal to bring testing near to the patient. TruenatTM MTB (Mycobacterium tuberculosis) and TruenatTM MTB-RIF (rifampicin) is an indigenous chip-based real-time polymerase chain reaction (PCR) based test for detection of multidrug-resistant (MDR) TB. The test involves extraction of DNA using automated, battery operated Trueprep instrument and real-time PCR performed on the Truelab analyzer. We report here multicentric validation of Truenat MTB-RIF for detection of DR-TB in suspected DR-TB patients.
Methods: Consecutive patients aged 18-65 yr, with symptoms suggestive of TB and with a history of previous treatment, reporting to the National TB Elimination Programme (NTEP) clinics under four national institutes, namely AIIMS (All India Institute of Medical Sciences, New Delhi), NITRD (National Institute of Tuberculosis and Respiratory Diseases, New Delhi), NIRT (National Institute for Research in Tuberculosis, Chennai) and ICMR-National JALMA Institute for Leprosy and other Mycobacterial Diseases, Agra, were included in the study. Two sputum samples (one spot and one morning) were collected from each patient, after obtaining informed written consent. The samples were subjected to smear, GeneXpert and MGIT 960 culture (and drug susceptibility testing to RIF) (surrogate for MDR-TB) to serve as reference tests. The samples were coded to ensure blinding and subjected to Truenat MTB-RIF. Truenat MTB-RIF Version 1.5 was used for testing 1084 samples for RIF resistance, while Version 2.0 was used to test another 1201 samples.
Results: Truenat MTB-RIF Version 1.5 in comparison with comprehensive laboratory reference standards yielded sensitivity and specificity of 76.2 and 94.7 per cent, respectively for the detection of RIF resistance in 1084 samples, collected across four sites. Based on the analysis of discordant samples, Version 2.0 of Truenat was developed by the manufacturer and this was further tested on additional 1201 samples, yielding a sensitivity of 87.5 per cent and specificity of 99.5 per cent.
Interpretation & conclusions: Multicentric trial of TruenatTM MTB-RIF demonstrated a great potential of this point of care NAAT for detection of MDR-TB. The test would be useful in limited resource settings and inaccessible areas without need for any additional infrastructure.