title: The Colour Test for drug susceptibility testing of Mycobacterium tuberculosis strains.
abstract: METHODS
  Tartu, Estonia.
  
  
  OBJECTIVE
  To assess the performance and feasibility of the introduction of the thin-layer agar MDR/XDR-TB Colour Test (Colour Test) as a non-commercial method of drug susceptibility testing (DST).
  
  
  METHODS
  The Colour Test combines the thin-layer agar technique  with a simple colour-coded quadrant format, selective medium to reduce contamination and colorimetric indication of bacterial growth to simplify interpretation. DST patterns for isoniazid (INH), rifampicin (RMP) and ciprofloxacin (CFX) were determined using the Colour Test for 201 archived  Mycobacterium tuberculosis isolates. Susceptibilities were compared to blinded DST results obtained routinely using the BACTEC™ Mycobacteria Growth Indicator Tube™ (MGIT) 960 to assess performance characteristics.
  
  
  RESULTS
  In all, 98% of the isolates produced interpretable  results. The average time to positivity was 13 days, and all results were interpretable. The Colour Test detected drug resistance with 98% sensitivity for INH, RMP and CFX and 99% for multidrug-resistant tuberculosis. Specificities were respectively 100% (95%CI 82-100), 88% (95%CI 69-97)  and 91% (95%CI 83-96) and 90% (95%CI 74-98). Agreement between the Colour Test and BACTEC MGIT 960 were respectively 98%, 96%, 94% and 97%.
  
  
  CONCLUSIONS
  The Colour Test could be an economical, accurate and simple technique for testing tuberculosis strains for drug resistance.  As it requires little specialist equipment, it may be particularly useful in resource-constrained settings with growing drug resistance rates.
authors: Department of Mycobacteriology, United Laboratory, Tartu University Hospital, Tartu, Estonia. Kadri.Toit@kliinikum.ee
authors: K
authors: K
authors: Toit
authors: S
authors: S
authors: Mitchell
authors: Y
authors: Y
authors: Balabanova
authors: C A
authors: CA
authors: Evans
authors: T
authors: T
authors: Kummik
authors: V
authors: V
authors: Nikolayevskyy
authors: F
authors: F
authors: Drobniewski
mesh_terms: D000995:Antitubercular Agents / Q000627:therapeutic use; D002939:Ciprofloxacin; D003116:Color; D024901:Drug Resistance, Multiple, Bacterial; D004957:Estonia; D054908:Extensively Drug-Resistant Tuberculosis / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D005240:Feasibility Studies; D006801:Humans; D007538:Isoniazid; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification; D011237:Predictive Value of Tests; D012293:Rifampin; D012680:Sensitivity and Specificity; D013997:Time Factors; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D002939:Ciprofloxacin; D007538:Isoniazid; D012293:Rifampin