Can someone with a positive indirect Coombs test (Indirect Antiglobulin Test) donate plasma?

Plasma Donation with a Positive Indirect Coombs Test

Individuals with a positive indirect Coombs test (Indirect Antiglobulin Test) can donate plasma for fractionation but are deferred from donating whole blood or components for direct transfusion. 1

Understanding the Indirect Coombs Test and Its Implications

The indirect Coombs test (Indirect Antiglobulin Test or IAT) detects antibodies in the serum that can react with red blood cells. A positive result may indicate:

• Presence of alloantibodies from previous transfusions or pregnancies 2
• Autoantibodies that may cause hemolytic anemia 3
• Antibodies related to certain infections or malignancies 4, 5

Guidelines for Plasma Donation with Positive IAT

Donation Eligibility

• Whole blood and components for transfusion: Donors with repeatedly reactive antibody tests are indefinitely deferred from donating whole blood and components intended for direct transfusion 1

• Plasma for fractionation: The FDA permits plasma from donors with repeatedly reactive antibody tests to be used for further manufacture into injectable products 1

Rationale for Different Standards

The different standards for plasma versus whole blood donation exist because:

• The manufacturing process for plasma derivatives (fractionation) can neutralize or remove potentially harmful antibodies 1
• It remains unclear whether antibody screening may adversely affect the safety of plasma-derived products, particularly immune globulins 1
• The FDA position on plasma donation from antibody-positive donors is subject to reevaluation as additional information emerges 1

Testing and Notification Protocol

When a donor tests positive for antibodies:

1. Initial reactive test: The sample should be retested in duplicate 1

2. If both repeat tests are non-reactive: The unit is considered non-reactive and the donor may return for subsequent donations 1

3. If either repeat test is reactive: The result is designated as repeatedly reactive 1

   • The donor is deferred from whole blood donation
   • The donor remains eligible for plasma donation for fractionation 1

4. Donor notification: Collection facilities must notify donors of repeatedly reactive test results and explain their deferral status 1

   • Notification should include written information presented either by sealed letter or face-to-face interview 1
   • Donors should be informed that the test result may be a false positive but could indicate infection 1
   • Referral to a physician is recommended for further evaluation 1

Special Considerations

• False positives: When screening populations with low prevalence of infection, the proportion of false-positive results will be high 1

  • The rate of anti-HCV repeat reactivity among U.S. blood donors has been reported at 0.5%-1.4% 1

• Supplemental testing: When available, supplemental testing may help interpret repeatedly reactive screening results 1

  • If supplemental testing is negative and ALT levels are normal, the initial test is likely a false positive 1
  • If ALT levels are elevated, physician referral is recommended regardless of supplemental test results 1

• Medical evaluation: Physicians evaluating donors with positive antibody tests should verify the presence of antibodies, assess whether the test result is a true positive, and determine if there is acute or chronic infection 1

Pitfalls to Avoid

• Do not assume a positive indirect Coombs test always indicates active disease; it may be a false positive or clinically insignificant finding 2

• Do not confuse guidelines for whole blood donation with those for plasma donation; they have different eligibility criteria 1

• Avoid misinterpreting test results without considering clinical context and supplemental testing when available 1