What Is Tuberculosis?
Mycobacterium tuberculosis infects more than 2 billion people. The leading risk factors for tuberculosis (TB) are poverty, HIV infection, and drug resistance. It is initially a lung disease that goes on to involve the bronchial tree, lymph nodes, and can even result in spread to distant sites. Late-stage disease involves destruction of lung tissue. TB is 2-3 times more frequent in older adults and immunocompromise increases the risk of being affected.
Primary TB: new TB infection in someone who has never had it. The most frequent symptom is fever (most common) and pleuritic/retrosternal pain (25%). On X-ray can be seen enlargement of lymph nodes in the hilar regions of the lungs in 65%, pleural effusions in 1/3, and pulmonary infiltrates (27%).
When a person ingests aerosol droplets from a person with TB, either:
- The organism is cleared
- The organism causes primary TB
- The patient develops latent infection
- A previous latent disease can become reactivated
Normal immunity causes 90% of infections to go into a “latent” phase. 10% progress to pneumonia and progressive infiltrates. Meningitis, pericarditis, or distant seeding can occur.
Reactivation TB: reactivation of a prior TB infection. Symptoms begin 2-3 years or longer after primary infection and include a low-grade fever, a cough, weight loss, fatigue, fever, night sweats, chest pain, and dyspnea.
Endobronchial TB: TB of the tracheobronchial tree. This results in difficulty breathing and distortion of the bronchi and bronchioles.
Complications of TB
Complications include coughing up blood (hemoptysis), pneumothorax from ruptured subpleural necrosis, bronchiectasis, progressive destruction of lung, septic shock, and increased risk of lung cancer and chronic pulmonary fungal aspergillosis.
How Is Tuberculosis Diagnosed?
Those at risk for new TB infection:
- Close and even casual contact with untreated persons with active TB
- Illicit drug use
- Those in institutionalized settings
- Health workers
Those at risk for reactivation:
- HIV infection
- Immunocompromise (transplant, chemotherapy, etc.)
- Renal failure (dialysis)
- Those on systemic steroids
- Those from TB-endemic countries
A tuberculin skin test should be performed in any person with a cough lasting for weeks, accompanied by lymph node enlargement, fever, and weight loss. A positive test only indicates exposure and possibly active infection. This test is useful for identifying latent TB.
TB diagnosis is established by isolating M. tuberculosis from bodily secretions such as sputum, bronchial lavage, pleural fluid, or tissue (lung/pleural biopsy). Another test is to test for acid-fast (stain) bacteria and nucleic acid amplification. X-rays are supportive tools only.
Tests for drug-resistant TB are necessary when there has been prior TB treatment or progression while on TB medication. Culture of the Mycobacterium with sensitivity testing for anti-TB drugs will identify any drug-resistances.
Bronchoscopy can be done when other attempts to retrieve material for culture fail. When this is not definitive, tissue biopsy is the next step.
How Can I Manage Tuberculosis?
Tuberculosis can be cured, but this can only happen when a patient is compliant with his or her antitubercular therapy.
There is an initial intensive phase of therapy, followed by a continuation phase. As the first sortie of attack, a 4-drug regimen of antitubercular agents is used, synchronized for optimal antitubercular effect:
- Pyrazinamide This can be eliminated in pregnancy and liver disease
These are used for two months, followed by a 2-drug regimen for at least another 4 months:
If there are complications such as cavitation or continued positive sputum cultures, the continuation phase can be extended to seven months instead of two (total time 9 months).
Drug intolerance, side effects, lack of compliance, and unavoidable interruptions require an individualized approach based on the time of therapy and the severity of the disease.
Prevention of Tuberculosis
Prevention in Areas of Risk
Prevention of tuberculosis (TB) is most important in immumocompromised individuals and those in health care facilities. Since person-to-person transmission is usually from inhaling infected aerosol droplets, group activities such as singing and close dancing in institutions should be discouraged. Persons with a chronic cough should don a barrier to block the projectile aerosol droplets. Visitors should be screened for suspicious symptoms such as a positive cough history or travel to a TB-endemic area.
Prevention in Hospitals
In hospitals, use of isolation is protocol in those with positive skin testing or a history of primary TB. Healthcare workers and visitors should use a mask effective as a barrier for aerosolized droplets.
Diabetics should practice strict glycemic control. Those on systemic steroids or who are immunosuppressed (HIV) should practice caution in crowded places.
Prevention in High Risk Individuals
Those who are at increased risk for reactivation–HIV or anyone with prior primary TB–should be followed closely by his or her primary care physician for diagnostic tests that can identify active disease at the earliest opportunities. Those on systemic corticosteroids should be reminded of their risk so that they can report any chronic cough or acute dyspnea that develops.
Prevention in the Household
The best strategy for preventing TB from passing from household member to member is effective treatment of the TB of the affected individual. This means support of compliance for the intensive phase and continuation phase of therapy.