title: Risk factors for extensively drug-resistant tuberculosis: a review.
abstract: BACKGROUND
  Extensively drug-resistant tuberculosis (XDR-TB) is emerging as a global public health problem. Its treatment is more expensive and difficult, and the outcomes much severe. The identification of risk factors for XDR-TB is of paramount importance to design effective TB control strategies.
  
  
  OBJECTIVE
  To review published articles on risk factors for XDR-TB.
  
  
  METHODS
  We identified 249 English articles on PubMed, and 182 were excluded by the abstract. The remaining articles were retrieved for full-text detailed evaluation by authors, and 27 relevant articles were selected for final review.
  
  
  RESULTS
  Some risk factors were consistently present, mainly previous TB treatment and its length. Other conditions often associated were immigration, alcoholism and HIV coinfection. Pre-XDR-TB points to an increased risk of XDR-TB.
  
  
  CONCLUSIONS
  The information regarding determinants of XDR-TB is relatively weak. However, special emphasis should be given to minimize the risks of TB retreatment to prevent the emergence of highly resistant TB.
authors.affiliation: Master Programme in Medicine, Hospital de São João and University of Porto Medical School, Portugal.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Flor de Lima
authors.forename: Margarida
authors.initials: M
authors.lastname: Tavares
mesh_terms: D060085:Coinfection / Q000453:epidemiology; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data; D054908:Extensively Drug-Resistant Tuberculosis / Q000453:epidemiology* / Q000517:prevention & control / Q000628:therapy; D014943:Global Health; D015658:HIV Infections / Q000453:epidemiology; D006801:Humans; D011329:Prisoners / Q000706:statistics & numerical data; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology
keywords: XDR-TB; drug resistance; extensively drug-resistant tuberculosis; risk factors