Tuberculosis Flashcards
What is tuberculosis, how does it develop and what causes it?
Tuberculosis (TB) is a bacterial infection spread through inhaling tiny droplets from the coughs or sneezes of an infected person. TB is from an airborne infection called mycobacterium tuberculosis.
Pulmonary TB affects the lungs/throat and is infectious, but non-pulmonary TB is not infectious and can affect any part of the body.
What are the symptoms of TB?
- persistent cough that lasts more than three weeks and usually brings up phlegm, which may be bloody
- weight loss
- night sweats
- high temperature (fever)
- tiredness and fatigue
- loss of appetite
- swellings in the neck
How is pulmonary TB diagnosed?
Diagnosing pulmonary TB can be difficult, and several tests are usually needed.
• CXR
• Sputum culture
• Sputum microscopy – shows red/pink rods that are acid-fast bacilli (AFB)
What does primary TB look like on a chest x-ray?
There are no radiological features which are in themselves diagnostic of primary mycobacterium tuberculosis infection (TB) but a chest X-ray may provide some clues to the diagnosis:
- consolidation of the upper zone with
- ipsilateral hilar enlargement due to lymphadenopathy.
What does ‘healed primary TB’ look like on a chest x-ray?
Following an immune response to primary infection, a caseating granuloma forms which calcifies over time – this is known as a ‘Ghon focus’. A Ghon focus is a rounded, well-defined focus of calcific density (as dense as bone) usually located in the periphery of the lung. This chest X-ray shows a large, rounded calcified focus near the right hilum. The CT (not usually necessary) shows it is located in the lung peripherally.
What does ‘post-primary TB’ look like on a chest x-ray?
Post-primary TB (secondary TB or reactivation TB) is more common in immunocompromised individuals – for example those with HIV/AIDS, those on immunosuppressing drugs, or those with malnutrition or diabetes
The upper lobes are more commonly affected
Consolidation often extends to the hilum
The hilar structures may be distorted due to volume loss of the upper lobe
What does ‘healed post-primary TB’ look like on a chest x-ray?
Following an immune response to post-primary infection, the affected area often becomes scarred (fibrotic) and calcified. The combined fibrosis and calcification can be described as ‘fibro-calcific change’
What does ‘miliary TB’ look like on a chest x-ray?
Miliary TB is due to disseminated spread of mycobacterial infection. It can occur either at the time of primary infection or on disease reactivation – prognosis is poor. Very fine nodules are typically seen scattered throughout the lungs
Why would you need to test for latent TB?
In some circumstances, you may need to have a test to check for latent TB – where you’ve been infected with TB bacteria, but don’t have any symptoms. For example, you may need to have a test if you’ve been in close contact with someone known to have active TB disease involving the lungs, or if you’ve recently spent time in a country where TB levels are high. If you’ve just moved to the UK from a country where TB is common, you should be given information and advice about the need for testing. Your GP may suggest having a test when you register as a patient.
What is the Mantoux test, when is it used, why is it used and how does it work?
The Mantoux test is a widely used test for latent TB. It involves injecting a small amount of a substance called PPD tuberculin into the skin of your forearm. It’s also called the tuberculin skin test (TST). If you have a latent TB infection, your skin will be sensitive to PPD tuberculin and a small, hard red bump will develop at the site of the injection, usually within 48 to 72 hours of having the test. If you have a very strong skin reaction, you may need a chest X-ray to confirm whether you have active TB disease.
If you don’t have a latent infection, your skin won’t react to the Mantoux test. However, as TB can take a long time to develop, you may need to be screened again at a later stage. If you’ve had the BCG vaccination (Bacillus Calmette–Guérin (BCG)) you may have a mild skin reaction to the Mantoux test. This doesn’t necessarily mean you have latent TB.
What is the interferon gamma release assay (IGRA) test, how does it work and why is it needed?
The interferon gamma release assay (IGRA) is a blood test for TB that’s becoming more widely available. The IGRA may be used to help diagnose latent TB:
• if you have a positive Mantoux test
• if you previously had the BCG vaccination – the Mantoux test may not be reliable in these cases
• as part of your TB screening if you’ve just moved to the UK from a country where TB is common
• as part of a health check when you register with a GP
• if you’re about to have treatment that will suppress your immune system
• if you’re a healthcare worker
How is TB treated?
With treatment, TB can almost always be cured. A course of antibiotics will usually need to be taken for six months. Several different antibiotics are used because some forms of TB are resistant to certain antibiotics. If you’re infected with a drug-resistant form of TB, treatment with six or more different medications may be needed.
The treatment of TB is two phased. The first phase includes the use of four antibiotics (RIPE/PIER) for 2 months. After the initial phase, daily treatment is continued for 4months using isoniazid and Rifampicin
If you have this form of the disease, you’ll need to take a number of antibiotics for 6 to 9 months. These four medications are most commonly used to treat it (RIPE):
- Rifampicin
- Isoniazid
- Pyrazinamide
- Ethambutol
Common side effects
Reduced appetite, nausea, vomiting
Deranged LFT’Ss
Rifampicin increases metabolism, in the liver, of other medications – drug interaction. Reduced bioavailability of other medications (hepatic induction)
What precautions do you need to take if diagnosed with TB?
If you’re diagnosed with pulmonary TB, you’ll be contagious for about two to three weeks into your course of treatment. You won’t usually need to be isolated during this time, but it’s important to take some basic precautions to stop the infection spreading to your family and friends.
You should:
• stay away from work, school or college until your TB treatment team advises you it’s safe to return
• always cover your mouth when coughing, sneezing or laughing
• carefully dispose of any used tissues in a sealed plastic bag
• open windows when possible to ensure a good supply of fresh air in the areas where you spend time
• avoid sleeping in the same room as other people
• If you’re in close contact with someone who has TB, you may have tests to see whether you’re also infected. These can include a chest X-ray, blood tests, and a Mantoux test.
How is latent TB treated?
Isoniazid (INH): This is the most common therapy for latent TB. You typically take an isoniazid antibiotic pill daily for 9 months.
Rifampicin : You take this antibiotic each day for 4 months. It’s an option if you have side effects or contraindications to INH.
Isoniazid and rifapentine: You take both antibiotics once a week for 3 months under your doctor’s supervision.
Which vaccine is used for TB?
The BCG vaccine offers protection against TB, and is recommended on the NHS for babies, children and adults under the age of 35 who are considered to be at risk of catching TB.
