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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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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)
ISTC Training Modules 2008
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)
ISTC Training Modules 2008
Standards for Public Health
ISTC Training Modules 2008
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
ISTC Training Modules 2008
% 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.
Morrison J et al. Lancet ID 2008
pooled estimate
ISTC Training Modules 2008
Morrison J et al. Lancet ID 2008
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
ISTC Training Modules 2008
Transmission of M.tb
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
Evaluating Contacts & Determining Priorities
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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.
ISTC Training Modules 2008
Alternate Slides
ISTC Training Modules 2008
Purpose of ISTC
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
ISTC Training Modules 2008
Questions
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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)
ISTC Training Modules 2008
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
ISTC Training Modules 2008
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
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