TUBERCULOSIS IN HIV Flashcards
What is the difference in lifetime chance of reactivation of latent TB between an individual who is HIV positive and another who is HIV negative?
HIV positive: 10% chance per annum
HIV negative: 10% chance over lifetime
How much more likely is a HIV positive individual to develop active TB than a HIV negative individual?
20-40 times more likely
What proportion of AIDS related deaths around the world are attributable to TB?
Around one quarter
What are the clinical features of TB?
Fever
Night sweats
Weight loss
Haemoptysis
How does HIV change the typical appearance of chest radiograph in someone with HIV?
Lacks characteristic upper zone cavitatory disease
Replaced by pulmonary infiltrates, mediastinal lymphadenopathy and pleural effusions
Are HIV positive patients with pulmonary TB more or less likely to be AFB sputum negative?
More likely which makes this inexpensive and rapid test less sensitive.
What does MODS stand for in the context of TB diagnostic tests?
Microscopic observation drug susceptibility assay
What does the microscopic observation drug susceptibility assay tell you about TB?
Information on drug resistance
How does HIV affect ease of diagnosis of TB?
Tends to make it harder and render tests less sensitive
Which TB diagnostic tests are rendered less sensitive by HIV?
Sputum smear for AFB
Sputum liquid culture
NAAT
Histology of granulomas - less AFB present
TST - tuberculin skin test
Rapid immune-based tests
Which TB diagnostic tests are unaffected by HIV?
MODS (Microscopic observation drug susceptibility assay)
Which TB diagnostic tests are rendered more sensitive by HIV?
Urine LAM (lipoarabinomannan)
What is the prevalence of drug resistant TB in HIV positive patients when compared with HIV negative patients?
2-3 times higher
This is not due to increased susceptibility to these strains, but more because HIV positive patients will rapidly develop active disease
What is the anti-TB drug that TB is most commonly resistant to?
Isoniazid
How does HIV affect anti-TB drug resistance?
Increases likelihood of rifampicin resistances
How does HIV co-infection affect the anti-TB treatment regimens?
It doesn’t in itself although there may be indirect increase in resistance to certain drugs.
What is the standard and reliable anti-TB treatment regimens for those with pulmonary TB or extrapulmonary TB without cerebral involvement?
Rifampicin for 6 months
Isoniazid for 6 months
Pyrazinamide for 4 months
Ethambutol for 4 months
Which anti-TB drug is a potent P450 inducer which therefore has an effect on cART doses?
Rifampicin (a type of rifamycin)
What is alternative to rifampicin that has less of inducing effect of P450 enzymes and is therefore often safer when given in conjunction with anti-HIV cART?
Rifabutin
By how much does effective use of cART reduce risk of developing active TB?
60-90%
Are those with an undetectable HIV load and a good blood CD4 count at increased risk of TB than the general population?
Yes
Which cART drugs should be especially avoided with rifampicin?
Protease inhibitors
Why is a combination of protease inhibitor (as cART) and rifabutin (instead of rifampicin) still not a particularly good regimen to use in a HIV/TB co-infected patient?
Because protease inhibitors inhibit rifabutin metabolism.
What are the risk of starting early (within 2 weeks of diagnosis) concomitant use of cART and anti-TB treatment?
Risk of drug interaction
Overlapping toxicities and additive adverse effects
High pill burden
Risk of reduced patient adherence
Immune reconstitution inflammatory syndrome (IRIS)
What are the most commonly experienced additive adverse effects seen with concomitant use of cART and anti-TB treatment?
Hepatotoxicity
Peripheral neuropathy
Rash
Persistent nausea and vomiting
What is immune reconstitution inflammatory syndrome (IRIS)?
When cART actually worsens existing disease due to an inappropriate response by the newly invigorated immune system. Mechanism is unclear.
What are the risk factors for developing immune reconstitution inflammatory syndrome (IRIS) when cART is started too soon after administration of anti-TB medication?
Very low CD4 count
Disseminated TB
What are the clinical features of immune reconstitution inflammatory syndrome (IRIS)?
New or enlarging lymph nodes, cold abscesses or other focal tissue involvement eg tuberculous arthritis
New or worsening radiological features of TB
New or worsening CNS TB
New or worsening serositis (pleural effusion, ascites or pericardial effusion)
Worsening of constitutional symptoms
Worsening of respiratory symptoms (cough, dyspnoea or stridor)
New or worsening abdo pain accompanied by peritonitis, hepatomegaly, splenomegaly or abdominal adenopathy
How do we treat immune reconstitution inflammatory syndrome (IRIS)?
Normally can be managed without stopping cART or anti-TB medication
More serious disease especially when associated with cerebral or mediastinal disease is likely to cause compression of vital structures. In these cases, corticosteroids should be given. These patients need close monitoring.
