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

Contact Evaluation

Your name Institution/organizationMeetingDate

International Standard 16

ISTC Training Modules 2008

Contact Evaluation

Objectives: At the end of this presentationparticipants 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


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


Standard 16: Contact Evaluation

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.

(1 of 2)


Standard 16: Contact Evaluation

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.

(2 of 2)


Standards for Public Health


Morrison J et al. Lancet ID 2008

% 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.

pooled estimate

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


% 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.

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



Yield: Active TB and LTBI by Age

TB1 LTBI2

Children

< 5 years 8.5 30.4

5 –14 6.0 47.9

All < 15 7.0 40.4

Adults 6.5 64.6

1 = % of examined contacts with clinical and confirmed TB2 = % of examined contacts with latent TB infection


Transmission of M.tb


Transmission of M.tb

CASE CONTACT

Site of TB Cough Bacillary load Treatment

Closeness and duration of contact

Immune status Previous infection

Ventilation Filtration U.V. light

Environment

Droplet nuclei


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


100 µm

5 µm

Evaporation

Fate of M.tb Aerosols

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


Effect of Therapy on M.tbLo

g cf

u

Effective multi-drug therapy reduces bacillary load

Weeks

0 2 4 6 8 10 12 14 16 18 20 22 24


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


Indices of Infectiousness

Loudon RG. ARRD 1969;99:109-11

Source-Case Variables Tuberculin Reactors (%)among household contacts

Radiographic extent of disease

Minimal 16.1

Moderately advanced 28.3

Far advanced (cavitary) 61.5

Bacteriologic status

Smear –, culture – 14.3

Smear –, culture + 21.4

Smear +, culture + 44.3

Mean 8-hour overnight cough count

< 12 27.5

12-48 31.8

> 48 43.9


Prevalence of Infection in Contacts

Grzybowski S. BIUAT 1975;60:90

Source case status

Age (yrs) Smear +Culture ?

Smear –Culture +

Smear –Culture –

GeneralPopulation

0-4 29.1% 6.0% 6.5% 0.7%

5-9 35.9 12.4 6.2 0.9

10-14 39.5 14.1 19.1 2.2

15-19 47.0 18.1 18.1 4.2

20-29 51.5 32.9 43.4 10.5

30-39 59.2 52.2 46.2 21.3

40+ 61.1 50.3 47.9 38.5


Evaluating Contacts & Determining Priorities


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


Circles of Contacts

Index case

Household ContactsAverage 4 – 5/case

Out-of-Household Contacts(Work, school, social) Unknown number

Uninfected, 2

Infected, 3

Uninfected, 10

Infected, 5


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


Levels of Exposure

Closeness and duration of exposure:•Grading exposure settings

1.Size of a car2.Size of a bedroom3.Size of a house4.Larger than a house


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


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


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


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


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


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)

Treatment for LTBI: Priorities


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


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


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.


Alternate Slides


Purpose of ISTC


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


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

ISTC: Key Points


Questions


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:

A. Sputum smear positive for M. tuberculosis

B. Significant cough symptoms

C. Cavitary-disease on chest film

D. Extrapulmonary cervical lymphadenitis


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)


Contact Evaluation2. (Cont.) In regards to planning a contact evaluation for

this case, lowest priority for assessment would be: A. Assessment of the clinical factors that influence

infectious risk, such as the presence and duration of cough symptoms

B. Gathering information regarding age, health status (especially risk for HIV), and presence of TB symptoms in any close contacts

C.Evaluation of his outdoor football teammates as contacts

D.Evaluation of the size and ventilation of the office space, and the amount of contact time between co-workers and the patient


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:

A. Children <5 years of age

B. Spouses due to the extended duration of exposure

C. Persons with HIV infection

D. Both A and C

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

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