Skip to Content
UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: HLA Flow Crossmatch

Test Code(s): XMFLOWS / HCXMFLOWS (if Pre-Tx), XMFLOWB/ HCXMFLOWB (if Post-Tx)

CPT Code(s): 86825 x 2

Test Description: Test Component:

Includes flow cytometry crossmatch for T-cells (CD3+) and B-cells (CD19+) to test for HLA class 1 and 2 antibodies against a particular organ donor or potential donor.

Methodology: Flow Cytometry

Clinical Significance: Positive flow crossmatch may indicate increased risk of antibody mediated organ rejection.

Days Performed: Mon-Fri, 0800-1700.

Turnaround Time: Stat: 4 hours.
Routine: 2 - 3 working days.

Specimen Requirements

Specimen: Blood

Collection Container: Preferred: Red top

Collection Volume: Preferred: 4 mL
Pediatrics: 1 mL

Sample Analyzed: Serum

Volume Required: Preferred: 2 mL
Pediatrics: 0.5 mL

Specimen Processing: Note: above sample is for the recipient. Potential donor blood must also be collected and submitted, minimum of 9 mL of blood collected in sodium heparin or ACD anticoagulant. Patient serum and donor cells may be available frozen in the UWHC HLA Laboratory -- call for availability, and indicate if lab should use specimens from storage in the lab.

Specimen Transport: Transport patient specimen at room temperature or refrigerated to the UWHC HLA Lab, D4/231.
Donor specimen must be collected, transported at room temperature, and received in the laboratory no later than noon on working days and within 2 days of collection.

Stability: Ambient: Patient serum, 7 days
Refrigerated: Patient serum, 7 days
Frozen: Patient serum, two weeks


The laboratory will produce a report of the determination of "positive", "negative", or "indeterminate", based on the change in fluorescent signal (delta MESF) compared to a median channel shift (MCS) from a negative control serum. A median channel MCS value will be reported, and may be useful for the clinician to assess the risk of transplant despite a result of "positive".



Results must be considered in conjunction with other laboratory testing (i.e., Luminex antibody testing) and clinical risk factors prior to transplant.


 T-cell (CD3) Result

 B-cell (CD19)  Result


Clinical Interpretation





Negative: Compatible






Positive: Increased risk of rejection





 Positive (strong)


Possible Class 2 antibody and/or weak Class 1 antibody









Non HLA-specific antibody or anti-Cw antibody(pattern has been seen with weak Class 1 antibody)


 Positive (weak)



Weak antibody, possible non-HLA antibody


Test Limitations:

Patients undergoing antibody modulation by means of IvIg therapy and having recent treatment by antibody-based immunosuppressant drugs (Rituximab, Thymoglobulin, Campath, etc) may present with a false positive flow cytometric crossmatch while lacking donor-specific HLA antibodies. Please alert the UWHC HLA Laboratory to any recent (within 2 months) immunosuppressive therapy.

Additional Information:

This test was developed and its performance characteristics determined by this laboratory.  It has not been cleared or approved by the US Food and Drug Administration.  The FDA has determined that such clearance or approval is not necessary.  This test is used for clinical purposes.  It should not be regarded as investigational or for research.  This laboratory is certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA-88) as qualified to perform high complexity clinical laboratory testing.

Flow XM crossmatch HLA FLOWXM

Back to Lab Test Directory Index