Understanding Your Medical Test: A Patient's Guide to Laboratory Testing
A laboratory test that checks if a recipient has antibodies that might react against a donor's B cells before organ or stem cell transplantation.
{"This test checks compatibility between transplant recipient and donor","A positive result means higher risk of antibody-mediated rejection","The test uses flow cytometry to detect harmful antibodies","Both recipient serum and donor blood are required for testing","Results help doctors decide if transplantation is safe"}
Key facts at a glance
- LOINC
- 96049-2
- Short code
- BXMFC
- Synonyms
- B Cell XM Pt ser+Don bld Ql FC
- Category
- chemistry
- Sample
- serum
- Container
- Red top serum separator tube (SST) or plain red top tube for patient serum; ACD or EDTA anticoagulated tube for donor blood
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- flow-cytometry
- CPT
- 86807
- SNOMED
- 12736000
- Specimen volume
- 5-10 mL patient serum; 5-10 mL donor whole blood
- Stability
- Serum stable for 24 hours at room temperature, 7 days at 2-8°C, or 1 month at -20°C; Donor blood must be fresh (within 24-48 hours) for viable lymphocyte isolation
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test, and why has my doctor ordered it for me?
The B cell crossmatch test is a specialized laboratory test performed before organ or stem cell transplantation. It checks whether your immune system has produced antibodies that could attack the donor's B cells. B cells are a type of white blood cell that produce antibodies. If your body has already been exposed to foreign cells (through previous transfusions, transplants, or pregnancies), you may have developed antibodies that could reject the donor's cells.
How is this test performed, and what should I expect during the procedure?
A sample of your blood (serum) is mixed with cells from the potential donor. Flow cytometry, a highly sensitive technique, is then used to detect if any antibodies in your serum have bound to the donor's B cells. The test result is reported as either 'positive' (antibodies detected) or 'negative' (no antibodies detected).
What do the results of this test mean for my health and ongoing care?
A NEGATIVE crossmatch means no antibodies were detected, suggesting the transplant may proceed with lower risk of immediate rejection. A POSITIVE crossmatch indicates that antibodies were found that could attack the donor's cells, which may increase the risk of acute antibody-mediated rejection. Your transplant team will discuss whether special treatments are needed or if a different donor should be considered.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
No special patient preparation required; however, patient should be informed about the purpose of the test. Recent blood transfusions, pregnancies, or immunosuppressive therapy should be documented as they may affect results
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The B cell crossmatch is a critical pre-transplant compatibility test. A positive result is associated with higher risk of hyperacute or acute antibody-mediated rejection. This test helps transplant teams assess immunological risk and make informed decisions about donor selection, desensitization protocols, and post-transplant monitoring. The flow cytometry method offers higher sensitivity compared to traditional complement-dependent cytotoxicity crossmatch.
Frequently asked questions
Why do I need this test before transplantation?
How long does it take to get results?
What happens if my test is positive?
Does a negative result guarantee transplant success?
Sources
- 1
- 2
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.
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 16, 2026. · Read our editorial policy