Pulmonary tuberculosis

Background

Microbiology

• See Mycobacterium tuberculosis

Clinical Manifestations

• Presents as reactivation of latent infection months or years after primary tuberculosis
• Subacute or chronic cough (at least 2 to 3 weeks) eventually becoming productive and occasionally involving hemoptysis
  • Should be suspected in any patient with cough and HIV infection
• Constitutional symptoms, with fevers, night sweats, and unexplained weight loss
• Usually from reactivation of latent tuberculosis infection, and usually reactivates in lung apices
• May transiently improve with partially-active antibiotics such as fluoroquinolones

Diagnosis

• At least three consecutive sputum specimens, collected q8-24h, with at least one being an early morning specimen
• Spontaneous sputum, induced sputum, or bronchoalveolar lavage specimens
• Can be sent for either acid-fast staining of a smear and culture, or for PCR (e.g. GeneXpert)
• Chest x-ray may show signs of prior tuberculosis, including dense pulmonary nodules (with or without calcification) which can be hilar or upper lobe; small nodules with or without scarring/fibrosis in the upper lobes; upper lobe volume loss or bronchiectasis; pleural scarring

Management

• Empiric treatment for suspected drug-susceptible tuberculosis is RIPE x2mo then RI x4mo
  • Isoniazid 5mg/kg/d, max 300mg daily, with pyridoxine 25 mg po daily
  • Rifampin 10mg/kg/d
  • Pyrazinamide 25mg/kg/d, max 2g daily
  • Ethambutol 20mg/kg/d, max 1.2g daily, which can be dropped once susceptibility testing shows that it is pan-susceptible
• Standard duration for uncomplicated disease is 6 months total, though it is extended if high risk of relapse (see Special Populations, below)
• Treatment for multidrug-resistant tuberculosis is discussed separately

Special Populations

• For the elderly, or those at elevated risk of hepatotoxicity: can do induction phase without pyrazinamide and extend continuation phase to 7 months (from 4)
• For pregnant women: can consider dropping pyrazinamide and extending the course by 3 months, but if there is severe disease then likely should follow standard treatment
• For high risk of relapse, including extensive or cavitary disease in the first 2 months of treatment, culture-positivity after 2 months of treatment, or cavitary disease on CXR at end of treatment: the consolidation phase should be extended by 3 months (to 9 months total treatment)
• For severe liver disease:
  • Avoid rifampin, isoniazid, and pyrazinamide
  • Recommend a fluoroquinolone, ethambutol, and amikacin for 2 months followed by fluroquinolone and ethambutol for 18 months
  • Can consider adding rifampin if they are monitored closely

Adjunctive Therapies

• The addition of metformin to the induction regimen has been shown to speed resolution of radiographic findings, such as cavitations1
  • Metformin 500 mg p.o. daily for 1 week then 1000 mg p.o. daily for 7 weeks
  • No difference in conversion of sputum culture

Infection Control

• Airborne precautions until:
  • Treated for at least 2 weeks and symptoms are clearly improving
  • 3x negative sputum smears
  • They can be discharged home when clinical improvement, drug-resistant TB is not suspected and there is no contraindication for home isolation