title: Evaluation of the direct nitrate reductase assay for rapid detection of extensively drug-resistant tuberculosis.
abstract: METHODS
  Jiangxi, China.
  
  
  OBJECTIVE
  To evaluate the performance of the direct nitrate reductase assay (D-NRA) for rapid, low-cost detection of multidrug-resistant (MDR-) and extensively drug-resistant tuberculosis (XDR-TB) in high-burden, resource-limited settings.
  
  
  METHODS
  A total of 225 smear-positive sputum samples were collected from consecutive drug-resistant TB subjects. Samples were processed at the Province TB Reference Laboratory and tested for susceptibility to rifampicin (RMP), isoniazid (INH), ofloxacin (OFX), kanamycin (KM) and capreomycin (CPM) by D-NRA, using the indirect Löwenstein-Jensen proportion method (LJ-PM) as reference.
  
  
  RESULTS
  Of the 225 smear-positive sputum samples, 214 isolates were identified as Mycobacterium tuberculosis and analysed for further comparison. The sensitivity of the D-NRA in the detection of resistance to RMP, INH, OFX, KM and CPM was respectively 95.1% (97/102), 93.1% (135/145), 97.4% (76/78), 88.9% (40/45) and 90.6% (29/32); specificity was respectively 100% (112/112), 97.1% (67/69), 100% (136/136), 98.8% (167/169) and 96.7% (176/182). The median time to culture positivity was significantly shorter for NRA than for the indirect LJ-PM (14 days vs. 70 days, P < 0.001).
  
  
  CONCLUSIONS
  D-NRA showed high sensitivity and specificity in the rapid diagnosis of MDR- and XDR-TB in a high-burden, resource-limited setting.
authors.affiliation: Department of Clinical Laboratory, First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
authors.forename: Z-K
authors.initials: ZK
authors.lastname: Huang
authors.affiliation: Department of Clinical Laboratory, First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Luo
authors.affiliation: Intensive Care Unit, First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
authors.forename: C
authors.initials: C
authors.lastname: Qing
authors.affiliation: Department of Clinical Laboratory, First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
authors.forename: Y-T
authors.initials: YT
authors.lastname: Deng
authors.affiliation: Department of Clinical Laboratory, Jiangxi Chest Hospital, Nanchang, Jiangxi, China.
authors.forename: G-L
authors.initials: GL
authors.lastname: Xiong
authors.affiliation: Department of Clinical Laboratory, First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
authors.forename: J-M
authors.initials: JM
authors.lastname: Li
mesh_terms: D000328:Adult; D002207:Capreomycin / Q000494:pharmacology; D002681:China; D024901:Drug Resistance, Multiple, Bacterial; D054908:Extensively Drug-Resistant Tuberculosis / Q000175:diagnosis* / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology; D007612:Kanamycin / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000302:isolation & purification; D050901:Nitrate Reductase / Q000032:analysis*; D015242:Ofloxacin / Q000494:pharmacology; D011446:Prospective Studies; D012293:Rifampin / Q000494:pharmacology; D012680:Sensitivity and Specificity; D013183:Sputum / Q000187:drug effects / Q000382:microbiology
chemical_list: D002207:Capreomycin; D007612:Kanamycin; D015242:Ofloxacin; D050901:Nitrate Reductase; D007538:Isoniazid; D012293:Rifampin