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Pulmonary TB

Up HIV & TB Pulmonary TB TB meningitis


  • worldwide resurgence
  • exacerbated by the appearance of strains resistant to first-line therapy

Risk factors

  • Living in or originating from a developing country.
  • Age (< 5yrs, middle-aged and elderly men).
  • Alcoholism and/or drug addiction.
  • HIV infection.
    • in Western countries a significant percentage of patients with TB are infected with HIV
  • Diabetes mellitus.
  • Lodging house dwellers.
  • Immunosuppression.
  • Close contact with smear positive patients.
  • Silicosis.
  • Poverty and/or malnutrition.
  • Previous gastrectomy.
  • Smoking.

Clinical features

  • seldom found in asymptomatic individuals, even those with strongly positive tuberculin test (Heaf grade III or IV).
  • classical clincal features:
  • Cough productive of mucoid or purulent sputum.
  • Haemoptysis.
  • Chest wall pain.
  • Dyspnoea.
  • Localized wheeze.
  • Frequent "colds".
  • Unresolved pneumonia.
  • Fever and sweating.
  • Weight loss.
  • Lassitude.
  • Anorexia.
  • Dyspepsia.
  • Apical "crackles".
  • Hyponatraemia/ hypokalaemia.
  • Older patients, who may have co-existent chronic bronchitis, can be missed unless a chest X-ray is taken
  • May also present with pleural effusions, spontaneous pneumothorax and hoarseness or with enlarged cervical nodes or other manifestations of extra-pulmonary disease.
  • Clinical disease seldom found in asymptomatic subjects, even those with a Heaf grade III or IV tuberculin test
  • The presentation and management of TB in HIV positive patients is different

Investigations

Isolation of mycobacteria

  • Multiple sputum samples for microscopy for acid-fast bacilli and culture, preferably on different days.
  • Bronchial washings taken at bronchoscopy and gastric lavage samples should be obtained if sputum is not available.
  • Bronchoscopy and transbronchial biopsy may be useful in patients with suspected TB but negative sputum smear.
  • Advice on the collection and processing of specimens can be obtained from the Centers for Disease Control (CDC)

Chest X-ray

  • Essential.
  • Normal CXR almost excludes TB (except in HIV infected patients) but endobronchial lesions may not be apparent and early apical lesions can be missed.
  • Common appearances:
  • patchy/nodular shadowing in the upper zones (often bilateral)
  • cavitation
  • calcification
  • hilar or mediastinal lymphadenopathy occurs in the primary complex and may cause segmental or lobar collapse.
  • pleural effusion
  • dense round or oval shadows called "tuberculomas" can sometimes be seen
  • diffuse fine nodular shadowing throughout the lung fields in miliary TB.
  • Inactivity of disease cannot be inferred from CXR alone. Requires 3 -ve sputum samples and failure of any lesion seen on CXR to progress.
  • CXR appearances in HIV +ve patients with TB differ from non-HIV infected patients

Other investigations

  • Biopsy
  • Pleural biopsy often helpful.
  • Mediastinoscopy occasionally needed in patients with mediastinal lymphadenopathy.
  • Part of any biopsy specimen should always be sent for culture.

Treatment

6 month regime:

  • rifampicin 600 mg od 30 min before food (450 mg if < 50 kg weight)
  • isoniazid 300 mg od 30 min before food
  • pyrazinamide 2g (1.5g if < 50 kg weight) for 2 months
  • ethambutol 25 mg/kg for 2 months
    • Streptomycin can be substituted for ethambutol
  • Before treatment is started liver and renal function should be checked and visual acuity must be assessed if ethambutol is to be used. Ethambutol is not necessary for patients at low risk of infection with resistant organisms.
  • Pyridoxine for patients at increased risk of isoniazid induced peripheral neuropathy:
    • diabetes mellitus
    • chronic renal failure
    • malnutrition
    • alcohol abuse
    • HIV +ve
  • Recommendations for the management of adverse reactions can be obtained from the British Thoracic Society

Infection control

CDC guidelines

Isolation in isolation room with special ventilation characteristics, including negative pressure, for:

  • patients with infectious TB. Patient should be considered to be infectious if they:
    • are coughing or undergoing cough-inducing procedures
    • have +ve AFB smears and:
      • not on therapy or
      • just started treatment or
      • have poor clinical or bacteriologic response to chemotherapy
  • patients suspected of having active pulmonary TB

Hospitalized patients with active TB should be monitored for relapse by having sputum AFB smears examined every 2 weeks.

United Kingdom guidelines

Isolation for:

  • patients who are sputum smear positive
  • patients with bronchial washings which are smear positive if:
    • they are on a ward with immunocompromised patients or
    • known/suspected multi-drug resistant

Patients with non-drug resistant TB should be non-infectious after 2 weeks of treatment which includes rifampicin and isoniazid.

 

As TB is spread through aerosols it is probably appropriate to isolate patients who are intubated even if only their bronchial washings are smear positive.

Staff who have undertaken mouth-mouth resuscitation without appropriate protection, prolonged care of a high dependency patient or repeated chest physiotherapy on a patient with undiagnosed pulmonary TB should be managed as close contacts.

Prognosis

The outlook of patients with tuberculosis who require ICU admission is poor. In one retrospective study the in-hospital mortality for all patients with tuberculosis requiring ICU admission was 67% but in those with acute respiratory failure it rose to 81%.

Further reading

American Thoracic Society and Centers for Disease Control. (2000). Diagnostic standards and classification of tuberculosis in adults and children. Am. J. Respir. Crit. Care Med 161, 1376-1395. http://www.cdc.gov/nchstp/tb/pubs/1376.pdf

Centers for Disease Control. (1994). Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care facilities, 1994. Morbidity and Mortality Weekly Report 43, 1-141.

Joint Tuberculosis Committee of the British Thoracic Society. (1998). Chemotherapy and management of tuberculosis in the United Kingdom: recommendations 1998. Thorax 53, 536-548. http://www.brit-thoracic.org.uk/pdf/Chemotherapy.pdf

Small, P. M. and Fujiwara, P. I. (2001). Management of tuberculosis in the United States. N. Engl. J. Med 345, 189-200.

Joint Tuberculosis Committee of the British Thoracic Society. (2000). Control and prevention of tuberculosis in the United Kingdom: Code of practice 2000. Thorax 55, 887-901. http://www.brit-thoracic.org.uk/pdf/TB.pdf


©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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