Understanding Your Laboratory Test: What It Is, How It Is Performed, and What Your Results Mean
A pre-transplant compatibility test that checks if the recipient has antibodies that might react against the donor's B cells.
{"Determines if recipient antibodies could attack donor B cells","Critical test before kidney, pancreas, or heart transplantation","A positive result means higher risk of antibody-mediated rejection","Helps ensure donor-recipient compatibility","Performed using the recipient's serum and donor's blood cells"}
Key facts at a glance
- LOINC
- 48390-9
- Short code
- BXM
- Synonyms
- B Cell XM Bld Donr Ql
- Category
- chemistry
- Sample
- whole-blood
- Container
- ACD (acid citrate dextrose) tube (yellow-top) for both donor and recipient; alternatively, EDTA (lavender-top) or heparinized (green-top) tubes may be used depending on laboratory protocol
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Flow Cytometry Crossmatch (FCCM)
- CPT
- 86825
- SNOMED
- 127089005
- Specimen volume
- 10 mL whole blood for donor; 10 mL whole blood for recipient
- Stability
- Maintain at room temperature (18-25°C); process within 24-48 hours of collection. Do not refrigerate or freeze as this may affect cell viability.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
This test is a laboratory analysis that measures specific substances in a sample taken from your body. Your doctor may order it to check how well your organs are working, to screen for a medical condition, to confirm a suspected diagnosis, or to monitor how well a treatment is working over time.
The B cell crossmatch test is a laboratory test performed before organ transplantation. It checks whether the recipient (the person receiving the transplant) has antibodies in their blood that could react against the donor's B cells. These antibodies, if present, could potentially attack the transplanted organ and cause rejection.
The test is usually performed in a clinic, hospital, or laboratory. Depending on the type of test, a healthcare professional may draw a small sample of blood from a vein in your arm, ask you to provide a urine sample, or take a swab from the affected area. The sample is then sent to a laboratory, where trained staff analyze it and report the findings to your doctor, often within a few days.
A sample of the recipient's serum is mixed with the donor's blood cells in the laboratory. If the recipient's immune system has produced antibodies against the donor's B cell antigens, these antibodies will bind to the donor cells and cause a positive reaction. The test result is reported as either 'positive' (antibodies present) or 'negative' (no antibodies detected).
Your results show whether the measured values fall within the normal reference range for your age and sex. Values within the normal range generally mean that no problem was detected, while results that are higher or lower than normal may point to an infection, inflammation, organ dysfunction, or another condition that needs closer evaluation. Your doctor will interpret the results together with your symptoms, medical history, and other tests before recommending any treatment or follow-up.
A NEGATIVE crossmatch means no antibodies were detected, indicating the recipient is likely compatible with the donor. A POSITIVE crossmatch means antibodies were found that could react against the donor's cells, suggesting a higher risk of immediate or severe rejection. In most cases, a positive crossmatch means the transplant should NOT proceed.
Reference range
Negative (No donor-specific antibodies detected against B cells)N/A
No fasting required. Patient should be well-hydrated. Inform the laboratory of any recent blood transfusions, immunosuppressive therapy, or pregnancy history, as these may affect antibody profiles. Donor and recipient samples must be drawn within 24 hours of testing.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The B cell crossmatch is a critical safety test performed before organ transplantation, particularly for kidney, pancreas, and heart transplants. It helps identify the risk of antibody-mediated (hyperacute) rejection, where the recipient's immune system attacks the transplanted organ immediately after transplantation. A positive result indicates the presence of donor-specific antibodies, which can lead to acute rejection, graft failure, or the need for aggressive immunosuppressive treatment.
Frequently asked questions
Why is the B cell crossmatch important?
How long does it take to get results?
Can a positive crossmatch become negative over time?
Does a negative crossmatch guarantee transplant success?
What is the difference between T cell and B cell crossmatch?
Sources
- 1
- 2
- 3
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