Pulmonary TB Flashcards
Define TB
infection caused by bacteria of the Mycobacterium tuberculosis complex
Most common cause(s) of TB
Mycobacterium tuberculosis = number 1
Mycobacterium bovis
Mycobacterium africanum
How is TB predominantly spread in the UK?
Inhaling the bacterium in respiratory droplets that are released when a person with infectious active TB coughs
Define active TB
Evidence of symptomatic or progressive disease of the lung and/or other organs
- 54.4% pulmonary
Define latent disease
Persistent immune response to stimulation by Mycobacterium tuberculosis antigens, with no evidence of clinically active TB
What is multi-drug resistant TB?
Resistant to two first-line drugs (isoniazid and rifampicin), with or without any other drug resistance
What is extensively drug resistant TB?
MDR + resistance to fluoroquinolone and any of the three specialist second line injectable agents
TB risk factors
Being born in high prevalence areas e.g. India, Pakistan, Romania, Bangladesh, and Somalia.
Children less than 5 years of age.
Close contacts with a person with active TB
History of untreated or inadequately treated active TB infection.
Co-morbid conditions e.g. HIV, diabetes, on RRT, previous gastrectomy
Immunosuppresive drugs
Under-served groups
History of excessive alcohol, injecting drug users, and smokers.
Symptoms/signs of TB (pulmonary)
Weight loss, fever, night sweats, anorexia, or malaise.
Persistent productive cough, breathlessness, haemoptysis
Symptoms/signs of TB (extrapulmonary)
Lymphadenopathy (often cervical or supraclavicular)
Bone or joint pains, back pain, and joint swelling
Abdominal or pelvic pain, constipation, bowel obstructio
Sterile pyuria
Headache, vomiting, irritability, confusion, cranial nerve abnormalities
Skin lesions — e.g. erythema nodosum, lupus vulgaris
Breathlessness, chest pain, or ankle swelling = TB pericarditis
Investigations for TB
CXR - cavitation, pleural effusion, mediastinal or hilar lymphadenopathy, or parenchymal infiltrates, mainly in the upper lobes.
Three sputum samples for microscopy for acid-fast bacilli, Mycobacteria culture, and specialist molecular tests/drug sensitivity testing
If think extrapulmonary TB - joint or spinal XRs, abdo renal tract lymph node USS, urine dipstick + microscopy + culture, echo, CT chest/CNS/bones/joints
Specialist assessment - rapid diagnostic nucleic acid amplification tests if need a rapid diagnosis. May need sputum induction, bronchoscopy and lavage, gastric aspiration, organ-specific aspiration or biopsy, and CT or MRI scans.
People who have been in contact with a person with active TB should have screening - who does this include?
All household members. Close contacts (such as partner, house visitors, and close workplace contacts) if the person with TB has a positive sputum smear result. Casual contacts (such as most work colleagues) if the index person with TB is particularly infectious or if casual contacts are at increased risk of infection
What is the Mantoux test?
This is a type of tuberculin skin test where tuberculin is injected intradermally. The skin is inspected for signs of a local skin reaction (induration) after 2–3 days, and the test is considered positive at an induration of 5 mm or more.
What is the interferon gamma release assay (IGRA) test?
Blood test based on detecting the response of white blood cells to TB antigens. It is less likely to give false positive results compared with a Mantoux test and gives a rapid result.
Differentials
Viral URTI Asthma Chest infection COPD Lung fibrosis Lung cancer
Drug treatment for TB
Isoniazid (with pyridoxine) Rifampicin
Pyrazinamide
Ethambutol
for 2 months
Then isoniazid and rifampicin for another 4 months.
What is DOT?
Directly observed therapy
- where drug treatment is given under the observation of a key worker (three times a week) and the person is observed to swallow each dose of medication, can be done by video = VOT
This is to improve adherence, reduce the risk of stopping treatment early, and reduce drug resistance.
What is primary TB?
A non-immune host who is exposed to M. tuberculosis may develop primary infection of the lungs. A small lung lesion known as a Ghon focus develops (composed of tubercle-laden macrophages). The combination of a Ghon focus and hilar lymph nodes is known as a Ghon complex.
In immunocompotent people the intially lesion usually heals by fibrosis. Those who are immunocompromised may develop disseminated disease (miliary tuberculosis).
What is post-primary (secondary) TB?
If the host becomes immunocompromised the initial infection may become reactivated. Reactivation generally occurs in the apex of the lungs and may spread locally or to more distant sites.
The lungs remain the most common site for secondary tuberculosis. Extra-pulmonary infection may occur in the
central nervous system, vertebral bodies, cervical lymph nodes, kidneys, or GI tract.
How is latent TB treated?
3 months of isoniazid and rifampicin
OR 6 months of isoniazid (with pyridoxine)
How long are patients with meningeal TB treated for?
at least 12 months
+ given steroids
Rifampicin side effects
potent liver enzyme inducer
hepatitis, orange secretions
flu-like symptoms
Isoniazid side effects
peripheral neuropathy
hepatitis, agranulocytosis
liver enzyme inhibitor
Pyrazinamide side effects
gout
arthralgia, myalgia
hepatitis
Ethambutol side effects
optic neuritis
Who is the BCG offered to?
- all infants living in high incidence areas or with a parent or grandparent born in a high incidence country
- all infants with a parent or grandparent who was born in a country where the annual incidence of TB is 40/100,000 or greater.
- previously unvaccinated tuberculin-negative contacts of cases of respiratory TB
- previously unvaccinated, tuberculin-negative new entrants under 16 years of age who were born in or who have lived for a prolonged period (at least three months) in a high incidence country
- healthcare workers
- prison staff
- staff of care home for the elderly
- those who work with homeless people
