title: Active case finding for pulmonary tuberculosis using mobile digital chest radiography: an observational study.
abstract: BACKGROUND
  Mobile digital chest radiography (CXR) is used routinely to screen for pulmonary tuberculosis (PTB) in London among homeless populations, persons accessing drug treatment services and prisoners.
  
  
  OBJECTIVE
  1) To establish the sensitivity and specificity of mobile digital  CXR, and 2) to test the hypothesis that actively identified cases have reduced odds of sputum smear positivity vs. those presenting passively to health care services from the same populations.
  
  
  METHODS
  Sensitivity and specificity were calculated using a gold standard comparator of culture-confirmed  cases of PTB reported to the national surveillance system within 90 days of screening. Logistic regression was used to determine whether actively detected cases had reduced odds of smear positivity compared to passively detected cases after adjustment for confounding.
  
  
  RESULTS
  The intervention  had a sensitivity of 81.8% (95%CI 64.5-93.0) and a specificity of 99.2% (95%CI 99.1-99.3). After adjusting for confounding, there was evidence that cases identified through screening were less likely to be smear-positive than passively identified cases (OR 0.34, 95%CI 0.14-0.85;  likelihood ratio test P = 0.022).
  
  
  CONCLUSIONS
  Digital CXR achieves a high level of sensitivity and specificity in an operational setting; targeted mobile radiographic screening can reduce the risk of onward transmission by identifying cases before they become infectious.
authors.affiliation: Find and Treat, University College London Hospitals NHS Foundation Trust, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Story
authors.forename: R W
authors.initials: RW
authors.lastname: Aldridge
authors.forename: I
authors.initials: I
authors.lastname: Abubakar
authors.forename: H R
authors.initials: HR
authors.lastname: Stagg
authors.forename: M
authors.initials: M
authors.lastname: Lipman
authors.forename: J M
authors.initials: JM
authors.lastname: Watson
authors.forename: A C
authors.initials: AC
authors.lastname: Hayward
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006703:Ill-Housed Persons; D006801:Humans; D016015:Logistic Models; D008131:London / Q000453:epidemiology; D008297:Male; D008403:Mass Screening / Q000379:methods; D008952:Mobile Health Units; D011329:Prisoners; D011856:Radiographic Image Enhancement / Q000379:methods*; D013902:Radiography, Thoracic / Q000379:methods*; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D016320:Substance Abuse Treatment Centers; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D055815:Young Adult