Tuberculosis (TB) remains one of the top 10 causes of death in the world with 9.27 million new cases and approximately 1.7 million deaths in 2007.1-2 The highest TB incidence occurs in Asia and Africa (86%).1 The incidence is lower in the United States with 13,299 TB cases in 2007 and rates continue to decline in the United States.3 The HIV-positive population has a significantly higher incidence than the general population and deserves additional attention for TB.4
Tuberculosis is caused by Mycobacterium tuberculosis, an acid-fast bacillus (AFB). Acid-fast bacteria retain their staining color after being washed with acid-alcohol washes.5 Transmission of TB is person to person through inhalation of droplet nuclei in the air. The majority of patients infected with M. tuberculosis do not develop active, symptomatic, contagious disease; they are said to have latent tuberculosis infection.6 Approximately 10% of those patients will go on to have active disease if not treated. Risk is highest in the first 2 years after infection.6-7 Cell-mediated immunity is the body's main defense against TB.6
TB's main site of infection is pulmonary. Clinical presentation of pulmonary TB includes: productive cough, fever, weight loss, night sweats, and hemoptysis.6 Extrapulmonary TB can develop in sites including: genitourinary, skeletal, central nervous system, pericardial system.6 Disseminated TB can also occur in several parts of the body. Immunosuppression puts people at higher risk for forms of TB other than pulmonary.6
Targeted tuberculin skin testing is used to identify patients with TB infection. The Mantoux test is where tuberculin purified protein derivative (PPD) is injected intradermally on the inner portion of the forearm.6 The induration at the injection should be read within 48 to 72 hours.6 The size of the induration and the patient's risk determine whether the test is read as positive.6 Patients who have previously received the bacillus Calmette-Guerin vaccine in another country can have a positive skin test due to the vaccine.6 This vaccination is not recommended for most of the US population.6 The QuantiFERON TB-Gold test measures the level of interferon gamma released in a blood sample in response to PPD.8 This test can provide more rapid diagnosis confirmation than skin testing.8 Sputum cultures, chest radiographs, and drug susceptibilities are obtained at first suspicion of active disease.6
The goals of TB treatment include: controlling the spread of TB, reducing the development of drug resistance, and preventing relapse to active disease.9 A four-drug regimen comprised of isoniazid, pyrazinamide, rifampin, and ethambutol is initiated in suspected active TB infection.9 The combination therapy prevents selecting out drug-resistant organisms. Typical treatment for active disease includes an initial 2 month phase of four drugs and a continuation phase of 4 months (18 weeks) with two drugs.9 First-line drug treatment regimens for TB recommended by the Center for Disease Control and Prevention are listed ...