title: Prevalence and determinants of positive tuberculin reactions of residents in old age homes in Hong Kong.
abstract: OBJECTIVE
  To determine the prevalence of tuberculous infection and the predictors of positive tuberculin reactivity in old age home residents in Hong Kong.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  A questionnaire-interview and review of medical records were carried out, together with measurement of weight and height/arm span and assessment of nutritional status. A one-stage tuberculin skin test (TST) was performed using two units of PPD RT23. An induration > or = 10 mm was considered as positive.
  
  
  RESULTS
  Of 3682 residents (71.7% participation, mean age 82 years) who agreed to undergo a TST, 46.3% had a positive reaction. Factors associated with a significantly higher risk of a positive TST included being male, an ex- or current smoker and having a past history of tuberculosis (TB). Factors associated with reduced positive tuberculin reactivity included older age groups (> 70 years), a history of cancer and chronic obstructive pulmonary disease and low body mass index quartiles.
  
  
  CONCLUSIONS
  In old age homes, the high prevalence of latent tuberculous infection is responsible for the high rate of active TB due to reactivation. Early diagnosis and treatment are necessary to prevent transmission of disease in these crowded environments with susceptible individuals.
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Hong Kong SAR, China. mmwchan@hkucc.hku.hk
authors.forename: M
authors.initials: M
authors.lastname: Chan-Yeung
authors.forename: A H K
authors.initials: AH
authors.lastname: Cheung
authors.forename: D L K
authors.initials: DL
authors.lastname: Dai
authors.forename: F H W
authors.initials: FH
authors.lastname: Chan
authors.forename: K M
authors.initials: KM
authors.lastname: Kam
authors.forename: C M
authors.initials: CM
authors.lastname: Tam
authors.forename: C C
authors.initials: CC
authors.lastname: Leung
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000995:Antitubercular Agents / Q000627:therapeutic use; D003430:Cross-Sectional Studies; D005260:Female; D006707:Homes for the Aged; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D016015:Logistic Models; D008297:Male; D009169:Mycobacterium tuberculosis; D011237:Predictive Value of Tests; D015995:Prevalence; D012111:Residence Characteristics; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents