Plasma Donation False Positive Test Results: HIV/Hep Appeal Process (2026)

What Are False Positives in Plasma Screening?

Every plasma donation is screened for transfusion-transmissible infections (TTIs) including HIV, hepatitis B, hepatitis C, syphilis, and others. These tests are highly sensitive — meaning they catch most real infections — but they are not 100% specific, meaning they occasionally produce false positives (positive results in people without the disease).

Sensitivity vs. Specificity in Screening

• Sensitivity: How well a test detects the disease when it is actually present. High sensitivity means fewer missed cases but more false positives.
• Specificity: How well a test confirms absence of disease when the disease is not present. High specificity means fewer false positives but may miss some real cases.
• Screening vs. confirmation: Initial plasma screening uses highly sensitive tests (to catch all potential risks). Confirmatory testing uses highly specific tests (to rule out false positives).

The FDA requires plasma centers to use screening tests with very high sensitivity (often 99.5% or higher) for HIV, hepatitis, and syphilis. This high sensitivity is intentional — it is better to have false positives (which are later ruled out) than to miss a real positive result that would harm recipients.

Prevalence of False Positives

Common Causes of False Positive Results

False positives occur due to various biological, technical, and immunological factors. Understanding these helps explain why you may have received a false positive result.

Biological Causes

• Recent vaccination: Vaccines (especially for hepatitis B, MMR, or flu) can trigger temporary antibody production that may cross-react with screening tests, producing a false positive for the disease the vaccine prevents.
• Autoimmune disease: Conditions like lupus, rheumatoid arthritis, and Sjögren syndrome cause high levels of nonspecific antibodies that may react on screening tests.
• Recent infection (non-matching): A recent viral illness or even a common cold may trigger elevated immunoglobulin M (IgM) that cross-reacts with screening reagents.
• Pregnancy and postpartum: Pregnancy-related immune changes and postpartum hormone fluctuations can increase nonspecific antibody reactivity.
• Monoclonal gammopathy: Overproduction of a single type of immunoglobulin (sometimes present in aging donors or those with lymphoid disorders) can cause false reactivity.

Technical Causes

• Hemolysis: If your blood sample hemolyzed (red blood cells ruptured) during collection or processing, it can produce false positive results.
• Lipemia: High triglycerides or cholesterol in your blood can interfere with optical readings on automated screening machines.
• Sample contamination: Rare contamination during collection or processing can produce false results.
• Reagent lot variation: Slight variations in test kit batches can occasionally produce false positives.

Immunological Cross-Reactivity

• Syphilis false positives: Most common because RPR (rapid plasma reagin) is a nonspecific test that detects general antilipid antibodies, not syphilis-specific antibodies. Many conditions produce these nonspecific antibodies.
• Hepatitis C false positives: Can result from cross-reactivity with other viral infections or contamination with hepatitis C surrogate tests.
• HIV false positives: Rare with modern 4th generation tests, but can occur with cross-reactivity to other retroviruses or technical issues.

False Positives by Infection Type: Causes and Rates

Syphilis (RPR/VDRL) False Positives

Syphilis testing has the highest false positive rate of all plasma screening tests. RPR (rapid plasma reagin) is a nonspecific test that detects a general antilipid response, not syphilis-specific antibodies.

Common causes of false positive syphilis tests:

• Recent viral infections (EBV, CMV, HIV, hepatitis)
• Autoimmune diseases (lupus, rheumatoid arthritis, Sjögren syndrome)
• Recent vaccinations (MMR, hepatitis B, influenza)
• Malignancy (lymphoma, ovarian cancer)
• Pregnancy
• Chronic liver disease
• Advanced age (older donors have higher false positive rates)

Confirmation test: Syphilis is confirmed with FTA-ABS (fluorescent treponemal antibody absorption) or TP-PA (Treponema pallidum particle agglutination), which are syphilis-specific and resolve false positives.

Hepatitis B (HBsAg) False Positives

Hepatitis B surface antigen (HBsAg) false positives occur in 10-20% of positive screens, usually due to:

• Recent hepatitis B vaccination
• Resolved hepatitis B infection with lingering immune response
• Cross-reactivity with other infections or immunological conditions
• Sample contamination or hemolysis

Confirmation test: Hepatitis B core antibody (anti-HBc) and recombinant immunoassay (RIA) or chemiluminescence distinguish true HBsAg positives from false positives.

Hepatitis C (Anti-HCV) False Positives

Anti-HCV false positives occur in 15-30% of positive screens, often due to:

• Resolved hepatitis C infection with residual antibodies
• Cross-reactivity with other viral infections
• Autoimmune diseases with nonspecific antibodies
• Hemolysis or sample issues

Confirmation test: Hepatitis C RNA (HCV RNA) by PCR (polymerase chain reaction) is the gold standard. RNA tests detect active infection; antibodies alone do not.

HIV False Positives

HIV false positives are rare with modern 4th generation antigen/antibody tests (occur in fewer than 1% of positive screens) but can happen due to:

• Recent HIV vaccination trials (if you participated)
• Cross-reactivity with other retroviruses (very rare)
• Technical errors (sample mix-up, improper testing)
• Hemolysis or contamination

Confirmation tests: HIV Western blot or HIV-1/HIV-2 differentiation immunoassay, followed by HIV RNA by PCR if needed.

The Appeal and Confirmatory Testing Process

If you receive a positive result on plasma screening, do not panic. You have rights and options for confirmatory testing and appeals.

What Happens After a Positive Screening Result

1. Notification: The center physician informs you (usually by phone, never via mail/email for confidentiality) of the positive result. This is mandatory.
2. Explanation of results: The physician explains the screening test, that it may be a false positive, and that confirmatory testing is required.
3. Referral for confirmatory testing: The center refers you to a licensed clinical laboratory for confirmatory testing at no cost to you. This is required by FDA regulations.
4. Deferral status: You are deferred from plasma donation indefinitely (or until a negative confirmatory test is received).
5. Documentation: The center documents the positive result. If you later receive a negative confirmatory test, that negative result must also be documented and your eligibility restored.

Confirmatory Testing Process

Important: You are entitled to receive a copy of your confirmatory test results. If you were deferred due to a positive screen, request a copy of your negative confirmatory test to prove to any laboratory that you are uninfected.

Your Rights During the Appeal Process

• Right to explanation of the positive result in understandable terms
• Right to free confirmatory testing at a licensed laboratory
• Right to receive a written explanation of results from both the center and the confirming lab
• Right to request your results be reviewed by a center physician
• Right to appeal the deferral if you believe the result was in error
• Right to have the negative confirmatory result restored to your eligibility file
• Right to confidentiality — results should only be shared with you and as required by law

NDDR Listing and Permanent Deferral

If your confirmatory test is positive (not a false positive), you will be listed on the National Donor Deferral Registry (NDDR). This has important implications.

What is NDDR?

The National Donor Deferral Registry is a confidential database maintained by the AABB (American Association of Blood Banks) that lists individuals permanently deferred from plasma and blood donation due to transfusion-transmissible infections. The registry includes:

• Confirmed positive HIV tests
• Confirmed positive hepatitis B surface antigen (HBsAg)
• Confirmed positive hepatitis C antibody (with positive confirmatory test or RNA)
• Confirmed positive syphilis (if serology confirms treponemal infection)
• Other serious infectious diseases

NDDR Protections and Limitations

NDDR listing provides important safeguards:

• Registry check: All U.S. plasma centers check NDDR before accepting new donors. If you are listed, you cannot donate at any participating center.
• Confidentiality: NDDR data is confidential and accessed only by authorized center staff for verification purposes.
• Lifetime deferral (usually): Once listed for HIV, hepatitis, or syphilis, you typically remain listed for life. Some conditions may be subject to review, but this is rare.
• No removal for false positives: If you received a false positive initially but later tested negative, the negative result should be documented in your file at the center. NDDR listing should not occur with a confirmed false positive.

Key Point: False Positives Do Not Result in NDDR Listing

If your screening was positive but confirmatory testing is negative, you are NOT listed on NDDR. You are eligible to resume plasma donation. The positive screen is noted in your file as a false positive for reference, but it does not affect your donation status.

Prevention and Reducing False Positive Risk

While some false positives are unavoidable, certain behaviors can reduce the likelihood of triggering a false positive screening.

1. Space out vaccinations: If you know you will be donating regularly, schedule vaccinations (especially hepatitis B or flu) for after your planned donations, when possible. Allow at least 48 hours between vaccine and donation.
2. Manage autoimmune conditions: If you have lupus, rheumatoid arthritis, or another autoimmune disease, work with your physician to monitor disease activity. Flares increase false positive risk.
3. Avoid donation during acute illness: If you are recovering from a recent infection (even a cold), wait 2-3 weeks after full recovery before donating.
4. Maintain good nutrition: Malnutrition and certain deficiencies can affect immune response and testing outcomes. Eat a balanced diet.
5. Report medical history: Inform the screening nurse about vaccinations, autoimmune diseases, and recent illnesses. This context helps centers interpret results.
6. Request repeat screening if borderline: If you receive a positive screening, ask the center if they can repeat the initial screening (retest) before sending to confirmatory testing. Sometimes a retest clarifies the result.
7. Stay hydrated before donation: Hemolysis (red blood cell rupture) can occur if you are dehydrated at collection. Dehydration also concentrates antibodies, potentially increasing false positive risk.

Frequently Asked Questions

How common are false positives in plasma screening?

False positives occur in 0.5-3% of plasma screenings depending on the test. Syphilis has the highest false positive rate (30-50% of positives), while HIV has the lowest (fewer than 1%).

What should I do if I get a positive screening result?

Do not panic. Request confirmatory testing through the center's referral. The confirmatory test will clarify whether the result is truly positive or false. You are deferred pending the result.

Will a false positive result be on my record permanently?

The initial positive screening remains in your file as a "false positive" or "resolved" depending on confirmation results. This does not affect future donations. A confirmed negative confirmatory test restores your eligibility.

Can I donate at another center after a false positive screening?

Only if you have a negative confirmatory test. If the initial screening was at one center and the confirmatory test at another, bring documentation of the negative result to the new center.

Does a false positive get reported to NDDR?

No. Only confirmed positive results are listed on NDDR. False positives that are ruled out by confirmatory testing do not result in NDDR listing.