title: Comparison of Xpert MTB/RIF with line probe assay for detection of rifampin-monoresistant Mycobacterium tuberculosis.
abstract: The MTBDRplus line probe assay (LPA) and Xpert MTB/RIF have been endorsed by the World Health Organization for the rapid diagnosis of drug-resistant tuberculosis. However, there is no clarity regarding the superiority of one over the other. In a double-blinded prospective study, we evaluated the efficacy of the Xpert MTB/RIF on samples that were first tested by LPA under the revised national tuberculosis control program of India. A total of 405 sputum samples from suspected drug-resistant tuberculosis patients were included. Of these, 285 smear-positive samples were subjected to LPA. Seventy-two (25.8%) samples showed multidrug resistance, 62 (22.2%) showed rifampin monoresistance, 29 (10.3%) showed isoniazid monoresistance, and 116 (41.5%) were pan-susceptible. Six (2.1%) of the samples gave invalid results. Of the 62 rifampin-monoresistant samples by LPA, 38 (61.4%) showed rifampin resistance, while 21 (33.8%) were found susceptible to rifampin by Xpert MTB/RIF using cartridge version G4. Three (4.8%) samples gave an error. Of the 116 pan-susceptible samples, only 83 were available for Xpert MTB/RIF testing; 4 (5.1%) were rifampin resistant, 74 (94.8%) were susceptible, and 5 (6.0%) showed an error. The 25 discrepant samples were further subjected to MGIT960 drug susceptibility testing. The MGIT960 results showed 100% agreement with LPA results but only 64.4% agreement with Xpert MTB/RIF results. Sequencing analysis of discrepant samples showed 91.3% concordance with LPA but only 8.7% concordance with the Xpert MTB/RIF assay. These findings indicate that by using Xpert MTB/RIF testing we might be underestimating the burden of drug-resistant tuberculosis and indicate that country-specific probes need to be designed to increase the sensitivity of the Xpert MTB/RIF.
authors.affiliation: Division of Clinical Microbiology and Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Syed Beenish
authors.initials: SB
authors.lastname: Rufai
authors.affiliation: Division of Clinical Microbiology and Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Parveen
authors.initials: P
authors.lastname: Kumar
authors.affiliation: Division of Clinical Microbiology and Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Amit
authors.initials: A
authors.lastname: Singh
authors.affiliation: Division of Clinical Microbiology and Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Suneel
authors.initials: S
authors.lastname: Prajapati
authors.affiliation: Division of Clinical Microbiology and Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Veena
authors.initials: V
authors.lastname: Balooni
authors.affiliation: Division of Clinical Microbiology and Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India sarman_singh@yahoo.com.
authors.forename: Sarman
authors.initials: S
authors.lastname: Singh
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001431:Bacteriological Techniques / Q000379:methods*; D004311:Double-Blind Method; D024881:Drug Resistance, Bacterial; D005189:False Positive Reactions; D006801:Humans; D007194:India; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000302:isolation & purification*; D011446:Prospective Studies; D012293:Rifampin / Q000494:pharmacology*; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D012293:Rifampin