U13W3: TB Flashcards
What is the legalities of informing a partner of a TB/HIV infection?
GMC
May discolse information to a person who is a close contact with a patient who has serious communicable disease if you have a reason to think that:
The person is at risk of infection that is likely to result in serious harm.
The patient has not informed them and cannot be persuaded to do so.
What is the TB action plan for England?
Launched in July 2021 by UKHSA
To improve prevention, detection and control of TB in England.
This includes the new entrant LBTI testing programme, increasing resources for TB services and targeting intervention at at risk groups such as asylum seekers and the homeless.
Most people with TB in Englands were….
born outside the UK
What are the most common risk factors for UK born population with TB?
Social risk factors
Drug or alcohol misuse
History of imprisonment
What were the most common social risk factors for TB amongst non UK born population?
Homelessness
Asylum seeker status
Mental health conditions.
What are TB rates in the UK like?
Highest in regions in central London
Also high in the North West and West Midlands
TB incidence is increasing - additional 6.5% in London and up 23.8% in North East
What is the purpose of bronchoalveolar lavage?
Sampling from deep within the respiratory ract including the alveoli
Normally done for patients unable to cough up sputum or when require analysis of deep lung conditions.
What are the key symptomatic presentations of TB?
Persistent cough
Fever
Night sweats
Weight loss
Chest pain
Fatigue
Loss of appetite
Coughing up blood.
What is the basic idea of the tuberculin skin test?
INject a small amount of purified protein derivative (PPD) derived from TB bacteria into the skin of the foraem.
After 48-72 hours any resulting induration is measured.
What is the basic idea of the IGRA test for TB?
Interferon Gamma Release Assays measure the production of interferon-gamma by T cells in response to specific antigens present in Mtb.
Blood samples are collected and incubated with these antigens in the laboratory, and the amount of interferon-gamma produced is measured.
How can the TST test lead to false positive results?
Due to cross reactivity with antigens from other mycobacteria or previous BCG vaccination
Sensitivity can also be affected by immunocompromised states.
Why is the specificity and sensitivity of the IGRA test better than the TST test?
IGRA - more specific antigens for Mtb are used
More sensitive - as results are not influenced by previous BCG vaccination, less likely to be a false positive
What other terms are used to refer to the TST tesk for TB?
Mantoux test
PPD (purified protein derivative)
Heaf test
How long does the IGRA and TST test take to get good results?
IGRA - few days for blood lab analysis
TST - 48 to 72 hrs - type 4 delayed hypersensitivity response
What are the different risk factors for TB?
Socioeconomic status - poverty, overcrowding, poor living conditions, malnutrition, lack of adequate healthcare and incarceration
Overall health/immune system: suppression, HIV co-infection, diabetes, TB within the last 2 years, transplant patients, malignancy
Alcoholism
Smoking
Drug users
Mental health (delay seeking care, mis doses)
Health care workers - exposure to category three organisms
Genetic predisposition
How does latent and extra pulmonary tb present different to active TB symptoms be?
Asymptomatic - particularly if latent
Extrapulmonary - symptoms specific to affected organs, e.g spine - back pain and spinal abnormalities, kidneys - flank pain and blood in urine.
What is the pathophysiological process of TB?
Infection beings with phagocytosis of bacteria by alveolar macrophages triggered by various receptors
In phagosome is subject to various killing mechanisms (may be cleared)
Mtb reproduces exponentially inside the macrophage and the alveolar space. Tissue dies in the centre of the granuloma (caseous necrosis) forms a Ghon focus.
If not contained within granuloma may enter local lymph nodes (lymphadenopathy enlarged and inflammed) - Ghon complex
Bacteria proliferate inside amac and migrate from lungs via blood stream to other tissue (military TB). More extensive damage occurs including cavity formation in the lungs.
Ghon complex enters a state of latents, may health with calcification, this contains the infection (forming a Ranke Complex)
Granulomas that don’t heal still contain viable bacteria and can be activated particularly if patient becomes immunocompromised
These new lesions typically occur at the lung apices.
How are the granuloma features in latent and active TB tend to be different?
Latent - Ranke complex - calcification - indicates has healed, is inactive
Active - caseous necrosis (does not normally occur in latent as bacteria are inactive)
Ghon complex and ghon focus can be associated with initial stages of disease that may lead to active or latent disease. Differentiation is based on whether bacteria are replicating and if symptomatic.
What pathoplogical land mark indicates the intitial site of infection with TB?
The ghon focos - site of granulomatous inflammation
The ghon complex - indicates the regional lymph node involvement
What are some presentation of systemic miliary TB?
Meninges - meningitis
Adrenal gland - addisons disease
Kidneys - sterile pyuria
Liver - hepatitis
Joints and bone - arthiritis and osetomyletisis
Lumbar vertebrae - Potts disease
Cervical lymph nodes - lymphadenitis in neck.
What is meant by pulmonary TB?
Infection starts in lungs
85% of cases
May spread to other parts of the body
What is extra-pulmonary TB?
Generally non-contagious
15% of cases
Occurs more frequently in immunosuppressed individuals
Most common sites are - military, lymph nodes, peritoneal, Potts disease, meningitis, skin (lupus vulgaris), genitourinary.
