Comprehensive Update on Tuberculosis Contact Investigation Strategies by Dr. David Shitrit

1. Update on Tuberculosis contact investigation Dr David Shitrit Maccabi Health Service Rehovot

2. TB Contact investigation

6. * When there is a history of a previous positive tuberculin skin test, tuberculosis or latent infection with M. tuberculosis, no tuberculin skin test should be administered ** BCG-vaccinated: chest X-ray only to avoid boosting of tuberculin skin test in 2d round * When there is a history of a previous positive tuberculin skin test, tuberculosis or latent infection with M. tuberculosis, no tuberculin skin test should be administered ** BCG-vaccinated: chest X-ray only to avoid boosting of tuberculin skin test in 2d round

7. The risk of progression to TB among contacts • A median incubation time of 6 weeks • Highest immediately after incubation time • Exponentially decline during the first 7 years • 60% in the first year • 80% < 2 years • After 7 years: 1 per 1000 person-yrs • Determined by the age: • 30-40% among infant • 2% primary school children

8. Likelihood and risk of transmission • Every TB patient should be interviewed promptly after diagnosis • Isolated extra pulmonary TB require CXR and sputum examination to exclude concomitant pulmonary disease. • The largest number of AFB is found in cavitary lesions • Smear negative, culture positive: 13% of all transmissions

9. Parameters to assess the infectiousness of the index patient Anatomical site: pulmonary TB The production of sputum Results of sputum smear examination Results of sputum culture Cavitation coughing

10. Infectious period • Onset of cough (or other respiratory symptom determine the onset of infectiousness • Pulmonary cases with positive smear: maximum of 3 months • Pulmonary cases with positive culture and 2 negative smear: 1 month • Until 2 weeks of appropriate treatment

11. Locations of transmission • Outdoors vs. Indoors • Specific investigation, preferably a visit is important

12. Susceptibility of the contacts

13. The tuberculin skin test • A positive reaction after 6-8 weeks from the infection • 14% anergy in TB children • 25% anergy in adults with HIV • Sensitivity • 95-99% in PPD>5 mm • 91-95% in PPD> 10 mm • 67-80% in PPD> 15 mm

14. Specificity of PPD • The longer the time since BCG and the larger PPD reaction size, the higher probability of TB • Possible causes of FN PPD • Age (below 6 months, above 65 yrs) • Cellular immune defects • Malignancy • Systemic high dose seteroids • Sarcoidosis

15. IGRA • In immunocompromised persons-more specific and sensitive than PPD • Less sensitive in immunocompetent pts than PPD • The specificity is much superior to PPD in immunocompetent with prior BCG • PPD should not perform in interval of 3 days from IGRA

16. Treatment regimens for Latent TB

17. Thank You!