title: Active case finding and prevention of tuberculosis among a cohort of contacts exposed to infectious tuberculosis cases in New York City.
abstract: BACKGROUND
  Tuberculosis contact investigation identifies individuals who may be recently infected with tuberculosis and are thus at increased risk for disease. Contacts with latent tuberculosis infection (LTBI) are offered chemoprophylaxis to prevent active disease; however, the effectiveness of this intervention is unclear as treatment completion is generally low.
  
  
  METHODS
  A retrospective cohort study of 30 561 contacts identified during investigation of 5182 cases of tuberculosis diagnosed in New York City, 1997-2003, was performed. We searched the NYC tuberculosis registry to identify contacts developing active tuberculosis within 4 years of follow-up. We estimated the following: number of contacts undergoing evaluation (ie, tuberculin skin test and/or chest radiograph) per prevalent case diagnosed; number of contacts with LTBI that need to be treated with standard chemoprophylaxis to prevent 1 active case.
  
  
  RESULTS
  Of 30 561 contacts, 27 293 (89%) were evaluated and 268 prevalent cases were diagnosed (102 contacts evaluated per prevalent case diagnosed, 95% confidence interval [CI], 90-115). LTBI was diagnosed in 7597 contacts, including 6001 (79%) who initiated chemoprophylaxis, 3642 (61%) who later completed treatment, and 2359 (39%) who did not complete treatment. During 4 years of follow-up, active tuberculosis was diagnosed in 46 contacts with LTBI, including 22 of 6001 (0.4%) who initiated chemoprophylaxis and 24 of 1596 (1.5%) who did not initiate treatment. The absolute risk reduction afforded by chemoprophylaxis initiation was 1.1% (95% CI, .6%-1.9%), leading to an estimated 88 contacts treated to prevent 1 tuberculosis case (95% CI, 53-164).
  
  
  CONCLUSIONS
  Contact investigation facilitates active case finding and tuberculosis prevention, even when completion rates of chemoprophylaxis are suboptimal.
authors.affiliation: Bureau of Tuberculosis Control, New York City Department of Health and Mental Hygiene, New York 11101, USA. hollyannanger@gmail.com
authors.forename: Holly A
authors.initials: HA
authors.lastname: Anger
authors.forename: Douglas
authors.initials: D
authors.lastname: Proops
authors.forename: Tiffany G
authors.initials: TG
authors.lastname: Harris
authors.forename: Jiehui
authors.initials: J
authors.lastname: Li
authors.forename: Barry N
authors.initials: BN
authors.lastname: Kreiswirth
authors.forename: Elena
authors.initials: E
authors.lastname: Shashkina
authors.forename: Shama D
authors.initials: SD
authors.lastname: Ahuja
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000904:Antibiotics, Antitubercular / Q000627:therapeutic use; D000995:Antitubercular Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D016358:Contact Tracing / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007538:Isoniazid / Q000627:therapeutic use; D055985:Latent Tuberculosis / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification; D009519:New York City / Q000453:epidemiology; D061366:Numbers Needed To Treat; D015995:Prevalence; D012189:Retrospective Studies; D012293:Rifampin / Q000627:therapeutic use; D014374:Tuberculin Test; D014376:Tuberculosis / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D055815:Young Adult
chemical_list: D000904:Antibiotics, Antitubercular; D000995:Antitubercular Agents; D007538:Isoniazid; D012293:Rifampin