Plasma donation is a life-saving process where the liquid component of blood is collected to create therapies for various medical conditions, including immune deficiencies and bleeding disorders. Individuals must pass a rigorous screening process before donating, which leads to questions about how recent medical procedures affect eligibility. Whether a recent tuberculosis (TB) test prevents donation depends entirely on which of the two primary types of TB tests was administered.
The Two Types of TB Tests and Their Impact on Donation
Tuberculosis testing uses two distinct methods that differ in their regulatory impact on plasma donation. The first method is the Tuberculin Skin Test (TST), widely recognized as the Purified Protein Derivative (PPD) or Mantoux test. This test involves a small intradermal injection of TB protein derivatives into the forearm. The second method is the Interferon-Gamma Release Assay (IGRA), a modern blood test requiring only a standard venipuncture. The distinction between injecting foreign material and a routine blood draw determines whether a donor must wait before giving plasma.
Immediate Eligibility When No Deferral is Required
If a healthcare provider uses the Interferon-Gamma Release Assay (IGRA) to screen for TB exposure, the donor is eligible to proceed with plasma donation right away, provided all other health criteria are met. The IGRA is a simple diagnostic blood test, meaning it only requires a standard venipuncture. This procedure does not introduce any foreign substances, vaccines, or biological materials into the body. Since the IGRA is just a blood collection, it does not trigger the temporary deferral periods associated with injections or vaccinations. Donors who choose this testing method can avoid unnecessary delays in their donation schedule.
Understanding the Temporary Deferral Period
The Tuberculin Skin Test (TST), or PPD test, requires a temporary deferral before a person can donate plasma. This waiting period is necessary because the PPD material injected under the skin must be examined for a reaction, typically between 48 and 72 hours after administration. Most plasma centers require donors to wait until the test has been officially read and the results documented by a licensed healthcare professional. The specific timing ensures the donation center has a complete medical history regarding the test outcome before collecting plasma.
Why the PPD Test Requires a Waiting Period
The requirement for a temporary deferral following a PPD test stems from the regulatory classification of the injected substance. The PPD material, a purified protein derivative, is considered a biological foreign material, similar to certain vaccines. When foreign proteins are intentionally introduced into the body, regulatory guidelines mandate a waiting period to ensure the donor does not experience any systemic adverse reaction. This measure safeguards the donor’s health and protects the safety of the plasma products derived from the donation. By classifying the PPD injection like a vaccination with foreign proteins, a brief deferral is enforced to mitigate potential complications and ensure product purity.