Well-quantified tuberculosis exposure is a reliable surrogate measure of tuberculosis infection

Int J Tuberc Lung Dis. 2012 Aug;16(8):1033-9. doi: 10.5588/ijtld.12.0027. Epub 2012 Jun 11.


Setting: Cape Town, South Africa.

Objective: To develop a standardized, reliable measure of household tuberculosis (TB) exposure that considers child-specific risk factors.

Design: We assessed TB exposure in 536 children. Children were considered Mycobacterium tuberculosis infected if two of three tests of infection were positive. Principal component analysis identified a discrete set of components that collectively described exposure and contributed to a composite contact score. Logistic regression assessed the odds of having M. tuberculosis infection given increasing contact score while controlling for age and past TB treatment.

Results: Four components described 68% of data variance: 1) maternal TB and sleep proximity, 2) index case infectivity, 3) duration of exposure, and 4) exposure to multiple index cases. Components were derived from 10 binary questions that contributed to a contact score (range 1-10, median 5, 25th-75th interquartile range [IQR] 4-7). Among children aged 3 months to 6 years with household exposure, the odds of being M. tuberculosis-infected increased by 74% (OR 1.74, 95%CI 1.42-2.12) with each 1-point increase in the contact score.

Conclusions: Well-quantified TB exposure is a good surrogate measure of M. tuberculosis infection in child household contacts in a high-burden setting, and could guide targeted preventive treatment in children at highest risk of M. tuberculosis infection.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Antitubercular Agents / administration & dosage
  • Chi-Square Distribution
  • Child
  • Child, Preschool
  • Communicable Disease Control / methods
  • Contact Tracing*
  • Drug Administration Schedule
  • Environmental Exposure*
  • Family Characteristics
  • Female
  • Housing
  • Humans
  • Infant
  • Interferon-gamma Release Tests
  • Isoniazid / administration & dosage
  • Logistic Models
  • Male
  • Mycobacterium tuberculosis / isolation & purification*
  • Odds Ratio
  • Predictive Value of Tests
  • Principal Component Analysis
  • Radiography, Thoracic
  • Risk Assessment
  • Risk Factors
  • South Africa
  • Sputum / microbiology*
  • Surveys and Questionnaires
  • Time Factors
  • Tuberculosis, Pulmonary / diagnosis*
  • Tuberculosis, Pulmonary / epidemiology
  • Tuberculosis, Pulmonary / microbiology
  • Tuberculosis, Pulmonary / transmission


  • Antitubercular Agents
  • Isoniazid