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C-reactive protein (CRP) donor-specific antibody screening in donor plasma

Published: August 9, 2026Updated: August 15, 2026

This test checks for antibodies in donated plasma that may react with C-reactive protein, a marker sometimes used in blood compatibility studies.

Quick summary

["Helps ensure donated blood is safe for transfusions by screening for potential immune reactions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
99787-4
Short code
cfDNA-KTX
Synonyms
cfDNA.donor/cfDNA.ttl p kid trnsplt
Category
chemistry
Sample
plasma
Container
Streck Cell-Free DNA BCT tube (preferred) or EDTA plasma tube (with rapid processing required)
Units
N/A
Ref low
0
Ref high
1
Critical range
— – 1 N/A
Fasting
false
Population
adult
Sex
all
Age range
0–99 years
Method
Next-Generation Sequencing (NGS) with single nucleotide polymorphism (SNP) analysis or targeted quantitative PCR for donor-derived cell-free DNA quantification
CPT
0494U (organ transplant monitoring, donor-derived cell-free DNA, next-generation sequencing, kidney)
SNOMED
444634007
Specimen volume
10 mL whole blood (yields approximately 4-5 mL plasma for cfDNA extraction)
Stability
Whole blood in Streck BCT: stable up to 7 days at room temperature (6-37°C). Plasma: stable for 1 month at -80°C; avoid repeated freeze-thaw cycles. EDTA whole blood must be processed within 4 hours of collection if Streck tube is unavailable.
Hemolysis max
200
Lipemia max
100
Icterus max
20
TAT
48–168 hours
Order
routine

What This Test Measures

This test detects the presence of antibodies in donor plasma that could bind to C-reactive protein, a substance often elevated in inflammation or infection. While CRP itself is not directly used in blood transfusions, its presence in donor samples may indicate a broader immune response that could theoretically affect compatibility testing.

Why It’s Done

Healthcare providers may order this test as part of a broader evaluation for blood donation screening, particularly if the donor has a history of immune-related conditions or if the plasma is intended for specialized therapeutic uses. It helps prevent transfusion-related immune reactions by identifying potential cross-reactivity risks.

How It Works

The test involves analyzing donated plasma for antibodies that may react with C-reactive protein using immunoassay techniques. If antibodies are detected, they are noted for further evaluation or exclusion from donation based on clinical guidelines.

What It Means for You

If your test result is positive, it may mean your plasma contains antibodies that could theoretically interfere with certain blood compatibility studies. This does not necessarily disqualify you from donating, but it may require additional testing or follow-up with a blood bank.

Reference range

Donor-derived cfDNA fraction (donor/total cfDNA): <1.0% considered negative/low risk for acute rejection. Values 0.5-1.0% warrant clinical correlation. Values >1.0% suggest active graft injury and warrant further investigation.N/A

Specimen: plasma

No fasting required. Avoid strenuous physical activity for 24 hours prior to collection as it may transiently elevate total cfDNA levels. Patients should be well-hydrated. Inform clinician of recent infections, surgery, or pregnancy as these may affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: This test is primarily used in the context of blood donation screening to assess potential immune compatibility risks. Elevated or reactive antibody levels may indicate an immune response that could theoretically impact transfusion safety, though CRP itself is not a direct transfusion marker. Results guide decisions about donation eligibility or further testing.

Short name

Donor CRP Antibody Screen

Frequently asked questions

What does a positive result mean?
A positive result means antibodies were detected in your plasma that could theoretically react with C-reactive protein. This may require further evaluation by a blood bank to determine if your donation should be excluded or if additional testing is needed.
Can I still donate if this test is positive?
Your ability to donate depends on local blood bank policies. Some centers may exclude donations with reactive antibody levels, while others may require additional testing or monitoring. Always contact your blood donation center for guidance.
Why is CRP being tested in donor plasma?
CRP is not a primary transfusion marker, but its presence in donor plasma may be part of broader immune compatibility assessments. The test helps identify potential cross-reactivity risks in specialized donation scenarios, such as therapeutic plasma exchange or antibody screening programs.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 15, 2026. · Read our editorial policy