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
- 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
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