Post on 27-Mar-2015
Contact Evaluation
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International Standards 18, 19
ISTC TB Training Modules 2009
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 TB Training Modules 2009
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
Contact Evaluation
International Standards 18, 19
ISTC TB Training Modules 2009
Standard 18: Contact Evaluation
All providers of care for patients with TB should ensure that persons who are in close contact with patients who have infectious TB are evaluated and managed in line with international recommendations. The determination of priorities for contact investigation is based on the likelihood that a contact:
1) Has undiagnosed TB
2) Is at high risk of developing TB if infected
3) Is at risk of having severe TB if the disease develops
4) Is at high risk of having been infected by the index case.
(1 of 2)
ISTC TB Training Modules 2009
Standard 18: Contact Evaluation
The highest priority contacts for evaluation are: Persons with symptoms
suggestive of tuberculosis Children aged <5 years Contacts with known or
suspected immunocompromise, particularly HIV infection
Contacts of patients with MDR/XDR tuberculosis
Other close contacts are a lower priority group
(2 of 2)
ISTC TB Training Modules 2009
Standards for Public Health
ISTC TB Training Modules 2009
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 TB Training Modules 2009
% 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 TB Training Modules 2009
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 TB Training Modules 2009
Transmission of M.tb
ISTC TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
Evaluating Contacts & Determining Priorities
ISTC TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
Priorities in Contact Evaluation
Contacts to MDR/XDR cases
• Prioritize active case-finding to reduce further transmission of drug-resistant disease
ISTC TB Training Modules 2009
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 TB Training Modules 2009
Isoniazid Preventive Therapy: 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 TB Training Modules 2009
Isoniazid Preventive Therapy: 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 TB Training Modules 2009
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)
Isoniazid Preventive Therapy: Priorities
ISTC TB Training Modules 2009
ISTC Standard 19: IPT
Children <5 years of age and persons of any age with HIV infection who are close contacts of an infectious index patient and who, after careful evaluation, do not have active tuberculosis, should be treated for presumed latent tuberculosis infection with isoniazid
ISTC TB Training Modules 2009
Contact Evaluation
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 TB Training Modules 2009
Contact Evaluation
Summary (continued): Priorities for evaluation include children
< 5 years of age, persons with HIV infection, contacts of MDR/XDR cases, and highly exposed contacts
Treatment of LTBI may be indicated for high priority contacts
ISTC TB Training Modules 2009
Summary: ISTC Standards Covered*
Standard 18: All providers of care for patients with TB should
ensure that persons (especially if symptoms suggestive of TB, children under 5 years of age, persons with HIV infection, and contacts to MDR/XDR) who are in close contact with patients who have infectious TB are evaluated and managed in line with international recommendations.
The determination of priorities for contact investigation is based on the likelihood that a contact: 1) has undiagnosed TB; 2) is at high risk of developing TB if infected; 3) is at risk of having severe TB if the disease develops; and 4) is at high risk of having been infected by the index case.
*Abbreviated version
ISTC TB Training Modules 2009
Summary: ISTC Standards Covered
Standard 19: Children < 5 years of age and persons of any
age with HIV infection who are close contacts of an infectious index patient and who, after careful evaluation, do not have active tuberculosis, should be treated for presumed latent tuberculosis infection with isoniazid
ISTC TB Training Modules 2009
Alternate Slides
ISTC TB Training Modules 2009
Purpose of ISTC
ISTC TB Training Modules 2009
ISTC: Key Points
21 Standards (revised/renumbered in 2009) 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 TB Training Modules 2009
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 TB Training Modules 2009
Questions
ISTC TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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 TB Training Modules 2009
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