TB Flashcards
How is TB transmitted?
Airborne transmission.
If TB is consumed by macrophages, there is no infection
If TB replicates in the lungs, cellular immunity activated -> latent TB.
If no robust cellular immunity, pt develops active TB and is symptomatic.
What is a significant risk factor for both latent and active TB?
HIV
Signs and symptoms of TB?
Productive cough, hemoptysis, fever, fatigue, night sweats and weight loss.
Radiological findings for TB?
Infiltrates in apical region of lung
Cavitary lesions
Difference between TB and pneumonia?
TB has a gradual onset.
Pneumonia has an acute onset.
Indication for latent TB infection screening?
High risk group AND intent to treat if positive.
High risk:
- children with recent TB contact
- HIV infected individuals
- patients considered for tumour necrosis factor antagonist therapy
- transplant patients
- dialysis patients
What are the two ways of latent TB diagnosis?
Tuberculin skin test (cutoff is 10mm) - false positive if BCG vaccination and environmental contact with non tuberculous mycobacteria. False negative if immunosuppressed. Inter reader variability.
Interferon-gamma release assay (need blood sample). No false positive in BCG vaccination. Minimal cross reactivity with non tuberculous mycobacteria. Results obtained faster within few hours. However, more expensive, need blood samples and false negative if immunosuppressed.
Infection control considerations?
For latent TB, no special precautions needed.
For active TB,
In hospitals, need airborne precautions. Treatment decreases infectiousness -> airborne precautions no longer needed after 2 weeks of effective treatment.
In community, no need to avoid household members bc risk of transmission while on effective treatment is low. Take TB medications, practice cough etiquette and ventilate homes.
Prior to initiating treatment for latent TB, what must be done?
- exclude active TB
- weigh risks vs benefits
Mono therapy is adequate. Helps to reduce lifetime risk of progression to active TB.
Treatment for latent TB?
Isoniazid: 5 mg/kg PO daily x 6 months (9 months if HIV) . Preferred regimen, especially in pregnancy, lactation and HIV. Coadminister with pyridoxine (at least 10mg/day) to minimise neuropathy.
OR
Rifampicin 10 mg/kg PO daily x 4 months (alternative in patients who cannot tolerate isoniazid)
What is the treatment for active TB?
Rifampicin: 10mg/kg daily OR 10mg/kg 3x/week (max dose is 600mg)
Isoniazid: 5mg/kg daily OR 15mg/kg 3x/week (max dose is 300mg if daily and 900mg if 3x a week)
Pyrazinamide: 15-30mg/kg daily (max dose is 2g)
Ethambutol: 15-25mg/kg daily (max dose is 1.6g)
Renal dosage adjustment needed for P and E.
What is the standard regimen for active TB?
Standard 6 month treatment:
Intensive phase for 2 months:
Daily administration of R, I, P AND E.
If there is confirmed susceptibility to R and I, OR culture negative TB, can step patient down to continuation phase of 4 months.
Daily or 3x a week administration of R and I.
If patient cannot tolerate pyrazinamide (P), what is the treatment like?
Standard 9 month treatment if unlikely to tolerate pyrazinamide (elderly or liver disease):
Intensive phase of 2 months:
Daily administration of R, I and E.
If confirmed susceptibility to R and I OR
Culture negative pulmonary TB, can step down to
Continuation phase of 7 months
Daily or 3x a week administration of R and I.
What type of killing does TB medications exhibit?
Concentration dependent killing, administer once a day.
Hepatotoxicity of TB medications?
R, I and P have hepatotoxicity.
Risk factors: age>35years, female, underlying liver disease, concurrent alcohol use, HIV.
Educate all patients on symptoms of hepatotoxicity. i.e.nausea,vomiting,unexplainedfatigue,
abdominal discomfort or pain)
If present, stop treatment and see doctor immediately.
