Contact Evaluation

1. Contact Evaluation Your name Institution/organization Meeting Date International Standard 16

2. Contact Evaluation Objectives: At the end of this presentation participants will be able to: • Describe how Mycobacterium tuberculosis (M.tb) is transmitted • Evaluate the risk of transmission based on the clinical extent of disease and diagnostic tests • Identify and evaluate contacts who are at increased risk for acquisition of infection • Determine who among contacts is at greatest risk should infection occur • Make decisions concerning the treatment of latent tuberculosis infection

3. Contact Evaluation Overview: • Value (yield) of contact evaluation • Transmission of M.tb • Clinical factors influencing transmission • Evaluating contacts and determining priorities • Vulnerable contacts • Treatment of infected contacts

4. Standard 16: Contact Evaluation (1 of 2) All providers of care for patients with tuberculosis should ensure that persons (especially children under 5 years of age and persons with HIV infection) who are in close contact with patients who have infectious tuberculosis are evaluated and managed in line with international recommendations. 

5. Standard 16: Contact Evaluation (2 of 2) Children under 5 years of age and persons with HIV infection who have been in contact with an infectious case should be evaluated for both latent infection with M. tuberculosis and for active tuberculosis.

6. Standards for Public Health

7. Yield of Contact Evaluations: All Active TB • On average, 4.4 household contacts were investigated per index case • 4.5% of evaluated household contacts will have active TB • Therefore, investigation of approximately 5 households yields one active TB case pooled estimate % of Contacts with Active TB (with or without positive bacteriology): Systematic Review. Graph compares results of individual studies in low- and middle-income countries. Pooled average of all studies indicated by arrow. Morrison J et al. Lancet ID 2008

8. Yield of Contact Evaluations: LTBI LTBI among household contacts • Nearly one-half of the household contacts evaluated had LTBI indicated by a positive tuberculin skin test, but a negative evaluation for active TB. pooled estimate % Contacts with LTBI: Systematic Review. Graph compares results of individual studies in low- and middle-income countries. Pooled average of all studies marked by arrow. Morrison J et al. Lancet ID 2008

9. 1 = % of examined contacts with clinical and confirmed TB 2 = % of examined contacts with latent TB infection Yield: Active TB and LTBI by Age Morrison J et al. Lancet ID 2008

10. Transmission of M.tb

11. Transmission of M.tb Droplet nuclei CASE CONTACT Environment • Site of TB • Cough • Bacillary load • Treatment • Ventilation • Filtration • U.V. light • Closeness and duration of contact • Immune status • Previous infection

12. Generation of Droplet Nuclei • One cough produces 500 droplets • The average TB patient generates 75,000 droplets per day before therapy • This falls to 25 infectious droplets per day within two weeks of effective therapy

13. Fate of M.tb Aerosols 100 µm Evaporation 5 µm • Large droplets settle to the ground quickly • Droplets < 100 m fall <1 meter before evaporating to 1-10 mm size • Smaller droplets form “droplet nuclei” of 1-5 µm diameter and can be inhaled and deposited in the distal airspaces • Droplet nuclei remain airborne indefinitely

14. Effect of Therapy on M.tb 0 2 4 6 8 10 12 14 16 18 20 22 24 Weeks Effective multi-drug therapy reduces bacillary load Log cfu

15. Assessing Infectiousness • High degree of infectiousness • Sputum smear-positive pulmonary TB • Symptomatic with cough • Cavitation on chest radiograph (correlates with positive smear) • Lesser degree of infectiousness • Sputum smear-negative, culture positive pulmonary TB • Minimal if any cough • Lesser radiographic extent of disease • Extrapulmonary TB

16. Indices of Infectiousness Loudon RG. ARRD 1969;99:109-11

17. Prevalence of Infection in Contacts Source case status Grzybowski S. BIUAT 1975;60:90

18. Evaluating Contacts & Determining Priorities

19. Decisions in Contact Evaluation • Deciding to initiate a contact evaluation • Investigating the index case and sites of transmission • Identifying contacts and assigning priorities • Evaluation of contacts • Treatment for contacts with latent tuberculosis infection

20. Circles of Contacts Index case Uninfected, 2 Uninfected, 10 Infected, 3 Infected, 5 Household Contacts Average 4 – 5/case Out-of-Household Contacts (Work, school, social) Unknown number

21. Identification of Contacts • Interview newly diagnosed TB patients to identify contacts • Focus on those in same household but don’t neglect out-of-household contacts • Tailor interview to patient’s circumstances (homeless, congregate living facility, etc.) • Determine the circumstances of exposure, and attempt to quantify the closeness and duration • Determine if there are other persons within the group of contacts who have symptoms associated with TB

22. Levels of Exposure Closeness and duration of exposure: • Grading exposure settings • Size of a car • Size of a bedroom • Size of a house • Larger than a house

23. Levels of Exposure Estimating critical exposure duration • Thresholds are highly variable • Exposure duration threshold should be determined by index case characteristics, settings, contact risk factors

24. Priorities in Contact Evaluation At greatest risk of acquiring infection • Close contacts of smear positive index cases • Persons with HIV infection (?) • Highly exposed persons At greatest risk of active TB • Children < 5 years of age • Persons with HIV infection • Persons with other immunocompromising conditions or therapies

25. Initial Assessments of Contacts Assessment depends on local circumstances, resources, and policies. • Minimal evaluation: Question contacts about symptoms and evaluate if symptoms are present • Tuberculin skin test followed by chest radiographs for all positives (either > 5 mm or > 10mm, depending on local policies) • Chest radiographs for all children < 5 years of age • Sputum examinations for all symptomatic contacts and all with radiographic abnormalities

26. Treatment for LTBI: Rationale • Risk of active tuberculosis is greatest soon after infection occurs • Contacts of infectious cases are likely to have been infected recently • Treatment of those found to have a positive tuberculin skin test will reduce the likelihood of active tuberculosis

27. Treatment for LTBI: Evaluation • Evaluate all potential LTBI treatment candidates for active TB • Identify those who have been treated previously • Identify those with contraindications to treatment for LTBI (prior allergic reactions, severe unstable liver disease) • Identify co-morbid conditions and other medications being used

28. Treatment for LTBI: Priorities • Children < 5 years of age • Persons with HIV infection • Persons with other immunocompromising conditions • Close contacts of highly infectious index case • Persons with other conditions that increase risk (example: silicosis)

29. Contact Investigation Summary: • Between 4 and 5 % of household contacts of new cases will be found to have active TB and 50% will have LTBI • The likelihood of transmission relates directly to the bacillary burden of the index case • Environmental factors also play an important role

30. Contact Investigation Summary: • Priorities for evaluation include children <5 years of age, persons with HIV infection, and highly exposed contacts • Treatment of LTBI may be indicated for high priority contacts

31. Summary: ISTC Standard Covered Standard 16: • All providers of care for patients with tuberculosis should ensure that persons (especially children under 5 years of age and persons with HIV infection) who are in close contact with patients who have infectious tuberculosis are evaluated and managed in line with international recommendations. • Children under 5 years of age and persons with HIV infection who have been in contact with an infectious case should be evaluated for both latent infection with M. tuberculosis and for active tuberculosis.

32. Alternate Slides

33. Purpose of ISTC

34. ISTC: Key Points • 17 Standards • Differ from existing guidelines:standards present what should be done, whereas, guidelines describe how the action is to be accomplished • Evidence-based, living document • Developed in tandem with Patients’ Charter for Tuberculosis Care • Handbook for using the International Standards for Tuberculosis Care

35. ISTC: Key Points • Audience: all health care practitioners, public and private • Scope:diagnosis, treatment, and public health responsibilities; intended to complement local and national guidelines • Rationale:sound tuberculosis control requires the effective engagement of all providers in providing high quality care and in collaborating with TB control programs

36. Questions

37. Contact Evaluation 1.A 23 year-old school teacher has recently been diagnosed with active pulmonary TB. She is concerned about the risk of transmitting disease to the children she teaches in a small, poorly-ventilated classroom. Aspects of her clinical presentation that would suggest a higher degree of infectious risk include all of the following except: Sputum smear positive for M. tuberculosis Significant cough symptoms Cavitary-disease on chest film Extrapulmonary cervical lymphadenitis

38. Contact Evaluation 2.A 42 year-old man has been diagnosed with smear-positive pulmonary TB. He works five days per week as an accountant in a small office with two other co-workers and lives in an apartment building with his wife and son. Other activities include a 2-hour weekly football game with his teammates outdoors. (Continued)

39. Contact Evaluation 2. (Cont.) In regards to planning a contact evaluation for this case, lowest priority for assessment would be:   Assessment of the clinical factors that influence infectious risk, such as the presence and duration of cough symptoms Gathering information regarding age, health status (especially risk for HIV), and presence of TB symptoms in any close contacts Evaluation of his outdoor football teammates as contacts Evaluation of the size and ventilation of the office space, and the amount of contact time between co-workers and the patient

40. Contact Evaluation 3.Contacts to an infectious pulmonary case of TB found to have latent TB infection (LTBI) who have the highest risks for progression to active TB disease once infected include: Children <5 years of age Spouses due to the extended duration of exposure Persons with HIV infection Both A and C