-
7/31/2019 190_Tuberculin Test _ Fact and Myth
1/17
Tuberculin Test
Fact & Myth
Magdy M Khalil
Prof. Chest Medicine, Ain Shams University
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
2/17
History
Tuberculin is an extract of tubercle bacilli
Robert Koch 1890: TB remedy Clemen von Pirquet 1890s: TB
immunity
Seibert 1930s: PPD
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
3/17
Mantoux test
ID, 0.1ml of PPD, 5TU
Reading after 48-72 h
Induration
Positive: 10 mm
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
4/17
Five years ago
32 ys old lady , pregnant 3rd trimester
R. cervical lymphadenopathy TB skin test: positive
Anti TB
Do you recommend TB test in this case?Q:
Anti TB for 3 months with good response
Delivered and stopped medications
Resumed anti TB medications 6 months later
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
5/17
Two weeks ago
R. thyroid swelling Ultrasound: Mass with breakdowns
TB skin test: positive
Referral to chest clinic for anti TB
Q: Do you recommend TB test in this case?
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
6/17
Natural history
Organism: Myc. tuberculosis
Entry
Respiratory tract
Alimentary tract
Skin
Immune response Cell-mediated immunity
Delayedtype hypersensitivity
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
7/17
InfectionLatent TB
No symptoms
No spread of infection Radiology ?
Microbiology: -ve
TB skin test: Positive (usually)
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
8/17
DiseaseTB
Symptoms: +ve
May spread infection Radiology: abnormal
Microbiology: positive
TB skin test: Positive (usually)
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
9/17
TBHealedOld May have radiographic findings
No symptoms or symptoms related to
fibrosis
TB skin test: Positive (Usually)
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
10/17
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
11/17
Facts Searching for diseases?
Positive TB skin test indicates infection;
not necessarily disease
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
12/17
Facts Screening for infection?
TB skin test is not absolutely
sensitive or specific for TB
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
13/17
Screening for TB infection?
Contacts
Anti TNF-alfa
Immigration
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
14/17
Highly +ve TB skin test?
Disease: No prognostic significance
Infection:
>25 mm ? Risk for active disease
Strong antigenic stimuliMore efficient response
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
15/17
TB skin test and BCG?
Distinguishing between a TB skin testreaction caused by
infection with M.tuberculosis and a reaction caused by
BCG is difficult However:
Larger induration
Contact with TBinterval between vaccination and testing
the greater is likelihood that the reaction
represents infection with M.tuberculosis
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
16/17
TB blood test?IFN- release assays (IGRAs)
QuantiFeron-TB Gold or T Spot-TB
Infectionspecificity (latent TB vs prior BCG)
Disease? sensitivity in detecting active TB
-
7/31/2019 190_Tuberculin Test _ Fact and Myth
17/17
Back to the lady!
Would you have recommended TB test?
[email protected]
