Upon completion of the chapter, the reader will be able to:
Compare the risk for active tuberculosis (TB) disease among patients based on their age, immune status, place of birth, and time since exposure to an active case.
Design an appropriate therapeutic plan for a patient with active TB disease.
Distinguish among the diagnostic tests used for patients potentially infected with TB.
Assess the effectiveness of therapy in TB patients.
Describe the common and important adverse drug effects caused by TB drugs.
Select patients for whom therapeutic drug monitoring (TDM) may be valuable and identify the necessary laboratory monitoring parameters for patients on antituberculosis medications.
Design appropriate antimicrobial regimens for the treatment of latent TB infection.
Tuberculosis (TB) remains one of the leading infectious causes of death worldwide. In 2012, about 8.6 million people developed TB and 1.3 million people died from the disease.1 Most deaths are preventable if access to health care for diagnosis and correct treatment are provided.
EPIDEMIOLOGY AND ETIOLOGY
KEY CONCEPT Roughly one-third of the world’s population is infected and drug resistance is increasing in many areas.1 The majority of cases worldwide are found in South-East Asia and Africa. In the United States, about 13 million people have latent TB infection (LTBI), evidenced by a positive skin test (purified protein derivative [PPD]) but no signs or symptoms of disease. The PPD is the antigen derived from Mycobacterium tuberculosis used to determine the presence of an immune response in patients with previous exposure. Patients testing positive have roughly a 1 in 10 chance of active disease during their lives, with the greatest risk in the first 2 years after infection. In 2013, 9588 new TB cases were reported in the United States; a 4.2% decline from 2012.2
The most recent data from the Centers for Disease Control and Prevention (CDC) indicate that TB deaths in the United States have increased slightly to 7.6%, from 529 deaths in 2009 to 569 deaths in 2010.3 (For details, visit the CDC website at www.cdc.gov/nchstp/tb.)
Risk Factors for Infection
Location and Place of Birth
California, New York, Florida, and Texas accounted for approximately 50% of all TB cases in 2013.2 These higher numbers may reflect the high immigration rates into these states.2 Mexico, the Philippines, Vietnam, India, and China account for the largest numbers of these immigrants.2 TB is most prevalent in large urban areas and is exacerbated by crowded living conditions.2 Those in close contact with patients with active pulmonary TB are most likely to become infected.2,3
Race, Ethnicity, Age, and Gender
In 2012, Asians accounted for 30% of new TB cases, followed by Hispanics (28%) and African Americans (22%), ...