title: Is early tuberculosis death associated with increased tuberculosis transmission?
abstract: BACKGROUND
  Tuberculosis (TB) is now a relatively uncommon disease in high income countries. As such, its diagnosis may be missed or delayed resulting in death before or shortly after the introduction of treatment. Whether early TB death is associated with increased TB transmission is unknown. To determine the transmission risk attributable to early TB death we undertook a case-control study.
  
  
  METHODS
  All adults who were: (1) diagnosed with culture-positive pulmonary TB in the Province of Alberta, Canada between 1996 and 2012, and (2) died a TB-related death before or within the first 60 days of treatment, were identified. For each of these "cases" two sets of "controls" were randomly selected from among culture-positive pulmonary TB cases that survived beyond 60 days of treatment. "Controls" were matched by age, sex, population group, +/- smear status. Secondary cases of "cases" and "controls" were identified using conventional and molecular epidemiologic tools and compared. In addition, new infections were identified and compared in contacts of "cases" that died before treatment and contacts of their smear-matched "controls". Conditional logistic regression was used to find associations in both univariate and multivariate analysis.
  
  
  RESULTS
  "Cases" were as, but not more, likely than "controls" to transmit. This was so whether transmission was measured in terms of the number of "cases" and smear-unmatched or -matched "controls" that had a secondary case, the number of secondary cases that they had or the number of new infections found in contacts of "cases" that died before treatment and their smear-matched "controls".
  
  
  CONCLUSIONS
  In a low TB incidence/low HIV prevalence country, pulmonary TB patients that die a TB-related death before or in the initial phase of treatment and pulmonary TB patients that survive beyond the initial phase of treatment are equally likely to transmit.
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Anu
authors.initials: A
authors.lastname: Parhar
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Alberta, Canada; Department of Medicine, Memorial University of Canada, St. John's, Newfoundland, Canada.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Gao
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Courtney
authors.initials: C
authors.lastname: Heffernan
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Rabia
authors.initials: R
authors.lastname: Ahmed
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Mary Lou
authors.initials: ML
authors.lastname: Egedahl
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Alberta, Canada; School of Public Health, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Long
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D016019:Survival Analysis; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000401:mortality* / Q000635:transmission; D055815:Young Adult