PUBLIC HEALTH

CDC Announces Shortage of TB Skin Test Antigen, New TB Testing Guidelines

The U.S. Centers for Disease Control and Prevention (CDC) announced a three-to 10-month national shortage of Aplisol (Par Pharmaceuticals; Chestnut Ridge, N.Y.), one of two purified-protein derivative (PPD) tuberculin antigens licensed by the Food and Drug Administration for use in tuberculin skin tests.

Interruption of supply for Aplisol 5 mL (50 multidose vials) began in June 2019, while interruption of the supply of Aplisol 1 mL (10 multidose vials) is anticipated in November 2019.

As a result of the shortage, CDC recommends three general approaches to prevent a decrease in tuberculosis testing capability. First, clinicians can substitute interferon-gamma release assay (IGRA) blood tests for tuberculin skin tests, with the caveat that clinicians should be aware that the criteria for test interpretation differ between the tests. Second, Tubersol can be used instead of Aplisol for skin testing. Previous studies have shown the two skin tests produce similar results.

“While overall test concordance is high, switching between PPD skin test products or between tuberculin skin tests and blood tests in serial testing may cause apparent conversions of results from negative to positive or reversions from positive to negative,” the CDC cautions. This may be due to inherent inter-product or inter-method discordance, rather than change in M. tuberculosis infection status.”

Additionally, the CDC is recommending consultation with state and local public health authorities in order to prioritize allocation of tuberculin skin tests to high-risk groups, while deferring others. Groups at high-risk for tuberculosis include: people who were recently exposed to persons with TB disease; people born in or who frequently travel to countries where TB disease is common; people living in large group settings, such as homeless shelters or correctional facilities; people with weaker immune systems; and children under the age of 5 years in one of the previously mentioned risk groups.

Annual TB testing of health care personnel is not recommended unless there is a known exposure or ongoing transmission (see box).

Health Care Personnel No Longer Need Annual TB Testing

U.S. health care personnel do not need routine, serial TB testing after a baseline test in the absence of a known exposure or ongoing transmission, according to recommendations from the National Tuberculosis Controllers Association and CDC, published May 17 in Morbidity and Mortality Weekly Report.

Based upon a systematic literature review that showed a low percentage of health care personnel have a positive TB test at baseline and upon serial testing, the joint workgroup revised the CDC’s 2005 TB testing recommendations for annual testing.

The revised recommendations call for baseline TB screening, including an individual risk assessment for all U.S. health care personnel. Postexposure, health care personnel should have a timely evaluation and additional testing, if warranted with either an interferon-gamma release assay or a tuberculin skin test. No routine, serial TB testing at any interval after baseline is called for in the absence of a known exposure or ongoing transmission.

Takeaway: Adjustments in tuberculosis testing will be needed during a nationwide shortage of Aplisol, a tuberculin antigen used in tuberculin skin tests. Changes in recommendations calling for only baseline TB testing among U.S. health care personnel may help with prioritization of testing during the shortage.

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