Plasma donation is a life-saving process where the liquid component of blood, rich in proteins and antibodies, is collected and used to create therapies for various medical conditions. Before donating, potential donors undergo a screening process to ensure the safety of both the donor and the plasma product. This screening includes questions about recent medical procedures, such as a test for Tuberculosis (TB), which is a bacterial infection primarily affecting the lungs. The type of TB test recently performed determines whether a person is immediately eligible to donate or if a temporary waiting period is required.
Waiting Period After a TB Test
The most common screening method for TB exposure is the Purified Protein Derivative (PPD) skin test, also known as the Mantoux test. This procedure involves a small injection of tuberculin antigens just beneath the skin of the forearm. Because the PPD test introduces a foreign protein into the body via injection, plasma donation centers institute a mandatory deferral period.
This deferral is typically in effect from the moment of the injection until the test result is formally read and documented by a healthcare professional. Most centers require a waiting period of at least 48 hours, extending up to seven or even 14 days, depending on specific policies. The donor must wait until the site is examined and the result is clearly recorded as negative before being eligible to donate. If the PPD test result is positive, the donor faces a significantly longer deferral or potential permanent exclusion until further medical clearance is provided.
Skin Tests Versus Blood Tests
The eligibility rules differ significantly based on whether a skin test or a blood test was used for TB screening. The PPD/Mantoux test requires the injection of the tuberculin antigen to elicit a localized skin reaction that is then measured. This injection of foreign material is the primary reason for the temporary deferral, as donation centers must monitor for any potential adverse systemic reactions.
In contrast, Interferon-Gamma Release Assays (IGRAs), such as the QuantiFERON or T-SPOT tests, are blood-based methods that detect the presence of TB infection. These tests involve only a standard blood draw, which does not introduce a foreign protein injection into the donor’s system. Consequently, the IGRA blood tests often do not require the initial mandatory waiting period associated with the PPD test. Donors who frequently give plasma may prefer the IGRA method to avoid the temporary deferral that interrupts their donation schedule.
Safety Concerns and Donor Screening
The deferral rules following a PPD skin test are in place to uphold the safety and integrity of the plasma supply. The primary concern is the injection of the tuberculin material itself, which is considered a non-vaccine foreign substance. Federal regulations generally require a deferral period after any non-vaccine injection to observe the donor for any delayed systemic reactions or signs of infection.
Screening for TB is part of a broader effort to ensure the donor is healthy and does not carry transmissible infectious diseases. Although the risk of transmitting TB bacteria through plasma is extremely low, the screening process minimizes all potential risks. Donors must be honest about all recent medical procedures, including the type and date of their TB test, to accurately determine eligibility. Proper disclosure allows staff to make an informed decision, protecting both the donor and the recipients of the final medicinal products.