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

2. TB Contact investigation

3. Conditions increasing the risk for progression to tuberculosis and relative odds (OR, from retrospective studies) or relative risk (RR, from prospective studies)
Condition
OR or RR
Immune suppression
HIV-positive and tuberculin skin test-positive [C]
AIDS68, 69 [C]
Solid organ transplantation related to immunosuppressant therapy 70 71, 72[D]
Receiving anti-TNF-alpha treatment [B]
Corticosteroids >15mg prednisolone equivalent per day for >2-4 wks 76, 77 [D*]
Malignancy
Haematological malignancy (leukemias, lymphomas) 78
Carcinoma of the head or neck and lung 79
Gastrectomy 80, 81
Jejunoileal bypass 82, 83
Silicosis 84-86
Chronic renal failure / haemodialysis 87, 88
Diabetes mellitus 89-92
Smoking 93-97
Underweight 98, 99
Age < 5 years (see table 3) 27
50-110
20-74
1.5-17
4.9
4-8 16
2.5
27-63 30
10-25
2-3.6
2-3
2-5

4. Classification of contacts around the index case according to the degree of exposure.
1st circle of contacts
(inner circle)
Close household contacts
Those who live in the same household as the infectious case.
Close non-household contacts
Contacts with regular, prolonged (more than an arbitrary minimum of 40 cumulative hours) contact with the source case, sharing breathing space but who do not live in the same household or who spent eight or more cumulative hours with the source case in a confined space, such a as a car, sweat shop or prison cell. These may also include contacts such as close friends and colleagues.
2nd circle of contacts
(middle circle)
Casual contacts
Those who spent less time with the infectious case. These may include frequent visitors to the home, friends, relatives, school or class mates, colleagues at work or leisure contacts and members of a club or team.
3rd circle of contacts
(outer circle)
Community contacts
Those living in the same community or attending the same school, sports club or workplace who may have had sporadic contact.

5. High priority contacts
Priority groups of contacts
High priority contacts
First circle contacts at increased risk of developing tuberculosis following infection
Other first circle contacts
Second circle contacts at increased risk of developing tuberculosis following infection
Medium priority contacts
Second circle contacts
Third circle contacts or middle circle
Low priority contacts
Third circle contacts or outer circle

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
Organization and timing of evaluation of contacts of infectious tuberculosis patient.
Contact group
Timing
< 1 wk after diagnosis
(or as soon as possible)
After window period
(8 weeks after end infectious period)
High priority
Vulnerable close contacts
Contacts with symptoms of tuberculosis
Tuberculin skin test*/IGRA and chest X-ray **
Tuberculin skin test /IGRA and chest X-ray
Other close contacts
Optional, or when proved transmission among (vulnerable) close contacts:
Tuberculin skin test /IGRA
Medium priority
Vulnerable casual contacts
When proved transmission among high priority contacts: Tuberculin skin test*/IGRA and chest X-ray
Other medium priority contacts
When proved transmission among high priority contacts:
Low priority
When proved considerable transmission among medium priority contacts: Tuberculin skin test /IGRA

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
Risk of meningeal/ disseminated TB
Risk of Pulmonary disease
Age at primary infection
10-20%
30-40%
<12 Months
2-5%
12-24 months
0.5% 5%
2-4 years
<0.5% 2%
5-10 years
>10 years

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
Level of evidence
Efficacy
Treatment regimen A
93%
12 months IZN C
90%
9 months IZN
69%
6 months IZN
Unknown (>3HR)
4 months Rifampicin
Equivalent to 6 IZN
3 months IZN+RIF(HR)

17. Thank You!