Pulmonary Tuberculosis

Background

• Pulmonary tuberculosis (TB) refers to the clinical syndrome associated with infection of the respiratory system caused by Mycobacterium tuberculosis.
• The World Health Organization estimates that in 2018, 10 million people developed TB and 1.5 million died from the disease, with 9,029 cases reported in the United States.
• M. tuberculosis is spread through the air from one person to another when bacteria are aerosolized from a person with pulmonary TB.
• Risk factors for developing TB include:
  • Close contacts of a person with infectious TB disease.
  • Children < 5 years old who have a positive tuberculin skin test.
  • Persons who have immigrated from regions of the world with high rates of TB.
  • Groups with high rates of TB transmission including persons with HIV infection, injection drug users, and homeless persons.
  • Working or residing with people at high risk for TB in facilities or institutions.
  • Medical conditions that weaken the immune system such as HIV infection, treatment with immunosuppressive medications, diabetes, malignancy, organ transplantation, silicosis, substance abuse disorder, severe kidney disease, or low body weight.

Evaluation

• Suspect pulmonary tuberculosis (TB) in patients with suggestive symptoms including fever, fatigue, weight loss, night sweats, cough, or hemoptysis.
• Identification of Mycobacterium tuberculosis in respiratory specimen confirms diagnosis of pulmonary TB in patients with compatible clinical symptoms.
• Tests used for bacteriologic diagnosis include:
  • Acid fast bacillus (AFB) smear microscopy, though this test is not specific to M. tuberculosis.
  • Nucleic acid amplification testing (NAAT).
  • Liquid and solid mycobacterial culture (gold standard for diagnosis).
• Diagnosis often supplemented with additional evidence such as:
  • Chest x-ray abnormalities.
  • Evidence of immune response by tuberculin skin test (TST) and/or interferon gamma release assay (IGRA), though these tests will also be positive in patients with previously treated TB or latent TB infection.

Management

• Tuberculosis (TB) is a reportable disease in the United States. Report all cases of suspected or confirmed TB to local health authorities and manage patients with TB in collaboration with Health Departments.
• Place hospitalized patients with suspected TB or who have an acid-fast bacilli (AFB) smear-positive sputum in airborne infection isolation with appropriate infection control measures for providers and visitors.
• The recommended empiric treatment for newly diagnosed pulmonary TB caused by Mycobacterium tuberculosis susceptible to all first-line drugs is a 2-month initial or intensive phase followed by a 4-month continuation phase (Strong recommendation).
  • The 2-month initial phase consists of isoniazid, rifampin, pyrazinamide, plus ethambutol.
  • The 4-month continuation phase consists of isoniazid plus rifampin.
  • The CDC has issued guidance regarding use of rifampin and rifapentine for treatment of active and latent TB infection after some manufacturers detect nitrosamine impurities in their products.
• Supplement isoniazid treatment with pyridoxine 25 mg/day in patients with nutritional deficiency, diabetes, HIV infection, renal failure, or alcoholism, in pregnant and breastfeeding women, and in children to prevent adverse events.
• Directly observed therapy (DOT) preferred over self-administered therapy (SAT) for routine treatment of patients with all forms of TB (Weak recommendation).
• Perform sputum smear microscopy at completion of intensive phase of treatment for smear-positive patients treated with first-line regimen. May also consider monthly sputum smears until two consecutive negative smears.
  • If specimen obtained at the end of intensive phase (month 2) is smear-positive, perform sputum smear microscopy at end of the third month.
  • If specimen obtained at end of month 3 is smear positive, perform sputum culture and drug susceptibility testing.
• If cavities are present on an initial chest radiograph and if a culture of a specimen obtained at 2 months remains positive, consider extending the continuation phase to 7 months (9 months total).
• All patients with TB caused by M. tuberculosis demonstrating drug resistance should be cared for by those with an expertise in the management of drug-resistant TB.