In June, CDC announced a nationwide shortage of Aplisol (Par Pharmaceuticals), a purified-protein derivative (PPD) tuberculin antigen. According to the agency, the shortage is expected to last 3 to 10 months, with a supply interruption of Aplisol 5 mL (50 tests) beginning in June 2019 and Aplisol 1 mL (10 tests) in November 2019 or sooner if demand increases before November. Aplisol is one of two PPD tuberculin antigens approved by FDA to perform tuberculin skin tests (TST) for the detection of latent Mycobacterium tuberculosis (TB) infection. The other is Tubersol (Sanofi Pasteur). Amid this shortage, CDC has released the following recommendations to mitigate the limited supply of Aplisol and prevent a decline in TB testing capability:▪Substitute interferon-gamma release assay (IGRA) blood tests for TSTs.▪Substitute Tubersol for Aplisol.▪Prioritize allocation of TSTs to at-risk groups in consultation with state and local public health authorities. According to the agency, the high-risk groups that take priority are as follows:▪People who have been recently exposed to persons with TB disease▪People born in or who frequently travel to countries where TB disease is common▪People who currently live or used to live in large group settings such as homeless shelters or correctional facilities▪People with weaker immune systems, such as those with certain health conditions or taking medications that may alter immunity▪Children, especially those younger than age 5 years, if they are in one of the risk groups mentioned above With the release of these new recommendations, CDC assured providers that the overall concordance among the different tests for TB disease is high. However, the agency cautioned that “switching between PPD skin test products or between TSTs and blood tests in serial testing may cause apparent conversions of results from negative to positive or reversions from positive to negative.” The agency explained that this may be due to “inherent inter-product or inter-method discordance, rather than change in M. tuberculosis infection status.” False-positive reactions may occur with TSTs. Causes may include, but are not limited to, infection with nontuberculosis mycobacteria, previous bacilli Calmette-Guerin (BCG) vaccination, incorrect method of TST administration, incorrect interpretation of reaction, and incorrect bottle of antigen used. IGRA blood tests or TSTs (but not both) can be used in most situations when testing for TB infection. However, when substituting IGRA blood tests for TSTs, CDC reminds clinicians that the interpretation criteria for IGRA blood tests differ from that of TSTs. Pharmacists should keep in mind that IGRA blood tests are preferred in persons who have received BCG either as a vaccine or for cancer therapy, as well as in individuals from groups that historically have had poor rates of return for TST reading. On the other hand, TSTs are preferred in children younger than 5 years because data are limited on use of IGRA blood tests in this patient population. In settings with low likelihood of TB exposure or infection, clinicians should consult with public and occupational health authorities and consider deferring routine serial testing. In addition, new CDC guidelines state that annual TB testing of health care personnel who do not have latent TB disease is no longer required. CDC reported that the United States saw a total of 9,029 new TB cases in 2018, which is a 0.7% decrease from the 9,094 cases in 2017. Among the 9,029 TB cases, 69.5% occurred in non–U.S.-born individuals, and 29.5% occurred in U.S.-born individuals. Alaska reported the highest incidence of TB in the nation, with 8.5 cases per 100,000 people. However, CDC said that four states—California, Florida, New York, and Texas—accounted for approximately one-half of the reported cases of TB in the country, “as has been the case for over 2 decades.” While the number of TB cases in the United States continues to decrease, the rate of decline has slowed. As such, CDC reported that the goal of eliminating TB in the country (annual incidence of < 1 case per 1 million persons) is unlikely to become a reality in the 21st century without increased investment and effort. Clinicians can monitor the status of the Aplisol shortage at www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/cber-regulated-products-current-shortages.
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