Tuberculosis Flashcards
What is the causative organism of TB?
Mycobacterium TB
What are the options that can occur on TB exposure?
Immediate clearance
Primary disease: Onset of active disease
Latent infection- Infection is contained and suppressed by the immune system. This can then re-activate to cause secondary infection
What are some symptoms of primary TB infection?
Haemoptysis Night sweats Fever Weightloss Fatigue
What might cause reactivation of latent TB?
Immunosupression
Anti TNF therapy
HIV
What investigation is done for TB?
Sputum culture- ZN/AFB staining, TB culture
Tuberculin Skin Test- Shows exposure to BCG or TB (therefore indicates latent TB too)
Interferon gamma release assay- more specific to TB
CXR- Apical cavitating nodules, effusions, hilar lymphadenopathy
If no sputum- may induce sputum or BAL
Biopsy of extrapulmonary sites- Caseating granulomas
ALWAYS DO A HIV TEST (REACTIVATION OCCURS WITH IMMUNOSUPPRESSION)
What might be seen on CXR for TB?
Upper lobe cavitating masses
Hilar lymphadenopathy
Pleural effusion
What are the majority of cases of active TB due to?
Reactivation in a patient with latent TB
This can occur with immunosuppression, HIV, anti TNF therapy
What is miliary TB?
Widespread TB that has spread via haematogenous spread. Causes milliarly seeded appearance on a CXR
What type of granuloma is seen in TB?
Caseating granuloma
Note non-caseating granulomas are seen in sarcoidosis.
Outside of the lungs where the other two most common places for TB to infect?
Lymph nodes
Gastrointestinal system
CNS and bone infection also common.
What is the treatment for active pulmonary TB?
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
6 months of top two
2 months at start with all four
What is a Ghon focus?
This is where the caesiating granuloma is
What is a Ghon complex?
Ghon focus and the lymph node involved with caseating granuloma
Undergo fibrosis and calcification making them visible on the CXR
What does TB cause with renal involvement?
Sterile pyuria
What does TB cause with adrenal gland involvement?
Addisons
What does the tuberculin skin test show?
It shows prior exposure to TB therefore may indicate active or latent TB
Immune reaction occurs within 48-72 hours
What test can be done to test for exposure to TB?
Tuberculin skin test
Interferon Gamma Release Assays (Blood test)
How long is rifampicin and isoniazid give for?
6 months
How long are ethambutol and pyrazinamide given for?
2 months
How might samples be obtained for AFB/ZN staining or TB culture?
Sputum
BAL
Induced sputum- nebulised salbutamol
Biopsy
What should you also test for in patients with TB?
HIV
What are some side effects of rifampicin?
Liver toxicity
Renal failure
Thrombocytopenia
What are some side effects of isoniazid?
Peripheral neuropathy
Liver toxicity
What are some side effects of pyrazinamide?
Liver toxicity
What are some side effects of ethambutol?
Rarely causes optic toxicity so baseline visual acuity should be checked.
Why is BCG vaccination contraindicated in HIV positive patients?
It is a live vaccine
If a patient is diagnosed with active TB what needs to be done?
Contact tracing
Test all family members, colleagues, classmates
Where should patients with suspected TB be kept in a hospital?
In side rooms
FFP3 face masks must be used when seeing them as well as standard PPE.
How can you test for latent TB?
Tuberculin skin test
Interferon gamma release assay
Why does latent TB occur?
Immune system prevents primary infection but this is done through granuloma formation where the mycobacterium are walled off to prevent spread. Granulomas are maintained with TNF alpha.
Who should be tested for latent TB?
Contacts of people with active TB
New healthcare workers
Immunocompromised patients
New entrants from high incidence countries
How is latent TB treated?
Isoniazid and rifampicin daily for 3 months
This reduces risk of reactivation later on
