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HIV & TB

HIV & TB. Worldwide TB is the most important opportunistic infection in HIV patients – its the commonest killer. Around 20 million people worldwide are co infected with HIV and TB.

vaughan-cantrell
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HIV & TB

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  1. HIV & TB

  2. Worldwide TB is the most important opportunistic infection in HIV patients – its the commonest killer. • Around 20 million people worldwide are co infected with HIV and TB. • Dual infection of HIV and TB is very low in Australia (sub Saharan Africa > 70%). < 5% of AIDS patients in Australia develop active TB. • 1-7% of the HIV infected people with latent TB, will go on to develop active TB each year – a risk that is 4-25x higher than in non-HIV patients. • TB affects the course of HIV infection: in vitro cytokines released because of Mycoplasma TB enhances HIV replication. • HIV patients newly infected with Mycoplasma TB are more likely to develop symptomatic primary infection.

  3. Clinical manifestation depends on: • CD4 status (level of immunosuppresion) • Whether the TB is from recently acquired TB or from a reactivation of latent TB. • HIV patients with preserved CD4 counts usually present with pulmonary TB. • Atypical manifestations, extra pulmonary or disseminated TB are more common in: • HIV patients with primary TB • Those with reactivated TB • Impaired immunity ( * CD4 count < 200 per microlitre)

  4. Tuberculin skin test should be part of the routine tests of every newly diagnosed HIV infection – test for latent TB. • Also all newly diagnosed patients with TB should be asked for HIV risk factors, and tested for HIV. • A Mantoux rxn of > 5mm is considered to indicated TB infection in people with HIV. • Occasionally patients with pulmonary TB can have normal CXR - unusual. • Diagnosis can be tricky particularly in advanced HIV: • Frequently negative sputum smear findings • Atypical radiographic findings • Higher prevalence of extra-pulmonary TB at inaccessible sites • Resemblance to other opportunistic pulmonary infections • Mycobacterium culture is most useful in Dx in such cases

  5. Rx of TB in HIV patients is complicated – only managed by expert doctors. • Rifampicin has pharmacokinetic interactions with protease inhibitors (PI) – via hepatic cytochrome p450. • There are also overlapping toxicities between HAART and anti-TB drugs: in particular hepatotoxicity, peripheral neuropathy and GI side effects. • In HIV patients not on HAART, standard TB therapy is good. • With those on HAART: • Rifabutin is used instead of rifampicin. • Or rifampicin could be used with efavirenz, or with ritonavir plus saquinavir. • Isonazid, ethambutol and pyrazinamide are used in standard doses. • MDR occurs in about 6% of cases of TB in HIV patients (2nd line Rx – aminoglycosides or quinolones). • Paradoxical treatment rxn – patients who begin HAART and anti-TB drugs at same times can develop fever, lymph gland enlargment or pulmonary infiltration week later – due to heightened immune response to mycoplasma TB secondary to HAART therapy.

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