Tuberculosis Flashcards
Mantoux interpretation
> 5 mm Positive
HIV-infected Immunosuppressed (TNFa, Tx, Close contacts of infectious TB Old TB on CXR
> 10 mm Positive
Medical risk factors (CRF, CA etc.) Foreign born endemic TB area HCW Nursing home, prisoners
> 15 mm Positive
All other persons BCG vaccinated
Interferon gamma release assay
Detects immune response to TB antigen
Cannot distinguish from active and latent TB
Once positive, always positive
Does not reflect severity or prognosis
Negative test does not always exclude TB
4 common extrapulmonary sites for TB
Lymph nodes
Bones and joints
Urine
Meninges/CNS
Presentation of TB meningitis
- 1% of TB
- Peak incidence children <4yrs
- Adults with HIV/ immunosuppression
- Subacute meningitis – 1wk-1m of fever, meningeal symptoms
- Focal neurology, seizures
- +/- pulmonary involvement
- Diagnostics
– AFB smear/ TB-PCR poor sensitivity
– MRI- basal meningitis
– CSF- lymphocytic pleocytosis, low glucose
Treatment of TB meningitis
Isoniazid, Rifampicin, Pyrazinamide and moxifloxacin for 8-12 months
Dexamethazone 6-8 weeks
Adverse effects of TB treatment
• Common even with first line agents
– ~10% serious AE
– Risk factors- Age >60, female, HIV+
– Generally in first 2 months of therapy
- Isoniazid- hepatitis, rash, neuropathy
- Rifampicin- drug interactions, hepatitis
- Pyrazinamide- hepatitis, skin, joint (gout)
- Ethambutol- optic neuropathy
TB treatment induced hepatitis
Pyrazinamide most common, followed by isoniazid and rifampicin
Liver safe drugs ethambutol, moxifloxacin, amikacin
Need to cease therapy if LFT >5x baseline or >3x and acute hepatitis
If can’t stop therapy, use liver safe drugs
Otherwise wait until LFTs reach baseline and restart one at a time
TB drug resistance types
Monodrug resistance - Isoniazid resistance
Multidrug resistant TB 5% world wide- resistant to isoniazid and rifampicin and additional resistance
Extensive drug resistant TB - resistant to isoniazid, rifampicin, quinolones, and 1 injectable - amikacin, capreomycin or kanamycin
Risk factors for drug resistance
Previous TB treatment
Contact with MDR TB infected patients
HIV
No clinical pattern predicts MDR
60-70% have no prior treatment
Treatment for MDR TB
‘Bangladeshi regimen’
• 9-12 months treatment
4 Isoniazid(2x dose), FQ, Pyrazinamide, Ethambutol,, Amikacin, prothionamide, Clofazimine
• 5-8 months
Pyrazinamide, Etambutol, FQ, Clofazimine
• Treatment success 80-90%
Indications for moxifloxacin in TB regimen
MDR-TB
Ethambutol required but contraindicated
IV therapy required or hepatotoxicity
Possible role in severe isoniazid resistant disease (BIII)
TB presentation in HIV CD4 <200
Most commonly extra-pulmonary
- Lymphadenopathy
- Miliary TB
- Meningitis
Pulmonary - non cavitating lesions, normally smear negative
CD4>200, will contract TB as any other non-HIV patient
Drug interactions NNRTI
– Efavirenz (EFV) 600mg (800mg if >60kg) + Rifampicin
– EFV (800mg) + Rifabutin (450mg) (Increases dose of both drugs)
– Rifabutin preferred with Etravirine/Rilpivirine/ Nevirapine
Drug interactions protease inhibitors
Rifampicin contraindicated, rifabutin at lower dose
Drug interactions integrase inhibitors
– Rifabutin preferred- usual dosing
– Double dose Raltegravir (50mg bd), Dolutegravir (800mg bd) if used with with rifampicin
– Elvitegravir (Genvoya/ Stribild) not with rifampicin
