Expected Shortage of TB Tests Prompts New CDC Recommendations

Veronica Hackethal, MD

June 20, 2019

The Centers for Disease Control and Prevention (CDC) has issued new recommendations for tuberculosis (TB) skin testing in response to the anticipated 3- to 10-month nationwide shortage of Aplisol (Par Pharmaceuticals), a purified-protein derivative (PPD) tuberculin antigen approved by the US Food and Drug Administration (FDA) for tuberculin skin tests (TSTs).

The report was published this week in MMWR.

The manufacturer has told the CDC they expect an interruption in Aplisol 5 mL (50 multidose vials) starting in June 2019, as well as an interruption of the supply of Aplisol 1 mL (10 multidose vials) starting in November 2019. However, the timeframe could change, depending on demand for the tests.

Aplisol is one of two FDA-approved PPD tuberculin antigens used for TSTs, along with Tubersol (Sanofi Pasteur).

Most cases of TB in the United States are diagnosed using a combination approach that includes one of these two TSTs and/or interferon-gamma release assay (IGRA) blood tests. Additional evaluation beyond skin tests and IGRA, such as chest X-ray and bacterial cultures, is needed to distinguish between latent and active TB.

The CDC's recommendations are intended to address the potential decrease in TB testing because of the shortage. Key points include:

  • Substitute IGRA blood tests for TSTs. (Note: The criteria for interpretation of IGRA blood tests are different than for TSTs).

  • Substitute Tubersol for Aplisol for skin testing.

  • Prioritize who receives TSTs, in consultation with state and local public health authorities. (Note: Some people may need to defer testing, depending on their risk for TB. Testing is recommended only in at-risk individuals and may not be needed when the likelihood of TB exposure is low. Annual testing of healthcare providers is not recommended unless they have been exposed to TB.)

According to the report, those at high risk for TB include individuals with recent contacts exposed to TB; individuals born in or with frequent travel to countries with high rates of TB; individuals who currently or in the past have lived in large group settings (such as homeless shelters or correctional facilities); immunocompromised individuals; children who fall into one of the previous groups, especially those younger than age 5 years.

Although studies suggest the results are similar for TSTs in most patients, the CDC cautions that switching between tests could lead to some individuals testing negative after an initial positive test and vice versa.

"Clinicians should assess test results based on the person's likelihood of infection and risk for progression to TB disease, if infected," according to the CDC.

The supply interruption will be updated at the FDA's Center for Biologics Evaluation and Research–Regulated Products: Current Shortages website.

MMWR. 2019;68:552-553. Full text

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