06/21/2019: Lab Advisory: Nationwide Shortage of Tuberculin Skin Test Antigens
Audience: Clinical Laboratory Partners and Laboratories
Level: Lab Advisory: Important information for a specific incident or situation; contains recommendations or actionable items to be performed by public health officials, laboratorians, and clinicians.
Nationwide Shortage of Tuberculin Skin Test Antigens
CDC is expecting a 3–10 month nationwide shortage of Aplisol, a product of Par Pharmaceuticals, and one of two purified-protein derivative (PPD) tuberculin antigens licensed by the Food and Drug Administration (FDA) for use in performing tuberculin skin tests.
Two types of immunological methods (tuberculin skin tests [TSTs] and interferon-gamma release assay [IGRA] blood tests) are used for detecting Mycobacterium tuberculosis infection. TSTs and IGRAs are used for the diagnosis of latent tuberculosis (TB) infection and can aid in the diagnosis of TB disease, but additional evaluation and testing is necessary to distinguish between latent TB infection and TB disease to determine the appropriate treatment.
Two FDA-approved PPD tuberculin antigen products are available in the United States for use in performing TSTs: Tubersol (Sanofi-Pasteur) and Aplisol. As a result of this shortage, clinical and public health laboratories should anticipate an increased demand for Tubersol and IGRA blood tests.
Recommendations for Patient Care and Public Health Practice
CDC recommends the following approaches for the expected shortage of Aplisol:
- Substitute IGRA blood tests for TSTs. Clinicians who use the IGRA blood tests should be aware that the criteria for test interpretation are different from the criteria for interpreting TSTs.
- Substitute Tubersol for Aplisol for skin testing. In studies, the two skin test products give similar results for most patients.
- Prioritize allocation of TSTs, in consultation with state and local public health authorities. Prioritization might require the deferment of testing some persons. CDC recommends testing only for persons who are at risk for TB. Groups at high risk for TB infection include
- Persons who are recent contacts exposed to persons with TB disease
- Those born in or who frequently travel to countries where TB disease is common
- Those who currently or previously lived in large group settings (such as homeless shelters or correctional facilities)
- Persons with compromised immune systems, including those with health conditions or taking medications that might alter immunity
- Children, especially those aged <5 years, if they are in one of the risk groups noted above
Although overall test concordance is high, switching between PPD skin test products or TSTs and blood tests in serial testing might result in apparent conversions from negative to positive or reversions from positive to negative that might be attributable to inherent inter-product or intermethod discordance rather than a change in M. tuberculosis infection status. Clinicians should assess test results based on the person’s likelihood of infection and risk for progression to TB disease, if infected.
For more information, see the Morbidity and Mortality Weekly Report (MMWR), June 21, 2019.