Key Point

All health care workers who test positive for TB should receive treatment.

NEW ORLEANS—Citing a recent report from the CDC,¹ Timothy R. Sterling, MD, and David W. Haas, MD, of Vanderbilt University School of Medicine in Nashville, called attention to some important aspects of the case, which involved transmission of Mycobacterium tuberculosis from a health care worker to patients: The health care worker was foreign-born and had previously been diagnosed with latent tuberculosis (TB) infection but had declined treatment; the worker developed active disease, which led to a large-scale investigation of the 1,500 patients who were exposed to the causative organism. The authors argue that all health care workers who test positive for TB should receive treatment.²

TB incidence in the United States is the lowest it has ever been. Most of the cases currently reported occur among foreign-born persons. According to Drs. Sterling and Haas, "One third of the world’s population, but less than 10% of the US population, has latent infection." They point out that a consequence of the increase in nonnative health care workers in the American workforce is a rise in latent TB.

THE DANGERS OF UNTREATED LATENT TB INFECTION

Bacille Calmette-Guérin (BCG) vaccination may confound the interpretation of the tuberculin skin test. Moreover, many immigrants assume that they are not at risk for active disease and do not need treatment because their latent infection has lasted for many years. The tuberculin skin test has low specificity, but the authors advocate using newer whole-blood assays—such as the recently approved QuantiFeron-TB Gold test—that detect the release of interferon-g by cells infected with M tuberculosis proteins. The CDC has established guidelines for the new assay’s use. BCG vaccination is less likely to confound results on this test than it is with the tuberculin skin test. The new test may have lower sensitivity than the older test, however.

"Treatment of latent tuberculosis infection should be provided to all health care workers who meet the established criteria, though public health laws do not mandate such treatment in persons who decline it," explain the authors. According to the CDC’s updated guidelines for the prevention of the transmission of M tuberculosis in health care settings, latent TB infection should be treated in health care workers who are at increased risk for progression to active disease.

The investigation of the case involving TB in the aforementioned health care worker revealed that few patients had become infected through exposure, and so far, no secondary cases of active TB have occurred. However, the authors warned that "a low frequency of adverse health outcomes often results in a perceived lack of urgency about treatment and makes it difficult to persuade people with latent tuberculosis infection to complete a course of treatment." Yet, the potential for transmission of the infection nevertheless exists and must be taken seriously.

Drs. Sterling and Haas concluded, "It is important that patients be able to trust their health care providers to ‘do no harm.’" They continue, "All heath care workers in the United States, regardless of their country of birth, must earn that trust by doing everything possible to minimize risk to patients." Therefore, adherence to the guidelines for the prevention of transmission of TB in health care settings must be followed. Treating latent TB infection is an important step towards achieving this goal.

—Tamara Gibb

Reference
1. Centers for Disease Control and Prevention (CDC). Mycobacterium tuberculosis transmission in a newborn nursery and maternity ward—New York City, 2003. MMWR Morb Mortal Wkly Rep. 2005;54:1280-1283.
2. Sterling TR, Haas DW. Transmission of Mycobacterium tuberculosis from health care workers. N Engl J Med. 2006;355:118-121.

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