Flowcytometry Crossmatching

What is Flow Cytometry Crossmatch test?

Flow Cytometry Crossmatch (FCXM) is a highly sensitive laboratory test performed before organ transplantation (most commonly kidney, but also other solid organs) to detect whether a transplant candidate has pre-formed antibodies that bind to a specific donor’s white blood cells (HLA on T and B lymphocytes). Detecting these donor-specific antibodies helps predict the risk of antibody-mediated rejection and informs transplant eligibility and peri-transplant management.

Why consider Flow Cytometry Crossmatch Test

• FCXM helps detect donor-specific anti-HLA antibodies with higher sensitivity than older complement-dependent cytotoxicity (CDC) crossmatch, reducing the risk of hyperacute and early antibody-mediated rejection and improving transplant safety.
• It enables separate assessment of antibody binding to donor T and B lymphocytes, refining risk stratification and guiding peri‑transplant decisions when combined with solid‑phase antibody testing and virtual crossmatch data.
• A negative FCXM supports proceeding with transplantation in many settings, while a positive result signals elevated risk that may warrant desensitization, altered immunosuppression, or selecting a different donor.
• FCXM’s increased sensitivity can identify clinically relevant donor-specific antibodies missed by CDC crossmatch, contributing to the near elimination of hyperacute rejection in modern practice.
• Awareness of FCXM limitations and interferences (e.g., therapeutic monoclonal antibodies like rituximab or daratumumab causing false positives) allows tailored protocols and confirmatory strategies to avoid misinterpretation.

Who should get this Flow Cytometry Crossmatch (FCXM) test?

Flow Cytometry Crossmatch is typically ordered in the following situations around solid-organ transplantation (most commonly kidney, but also heart, lung, pancreas, and others):

• Candidates being evaluated for a living-donor transplant to check for donor-specific anti-HLA antibodies before scheduling surgery.
• Candidates offered a deceased-donor organ when time permits, to confirm immunologic compatibility beyond a “virtual crossmatch.”
• Highly sensitized candidates (history of prior transplant, blood transfusions, or pregnancies) at increased risk of pre-formed donor-specific antibodies.
• Re-transplant candidates or those with known/borderline donor-specific antibodies on solid-phase assays (e.g., single-antigen beads), to better quantify cell-bound reactivity on donor T and B cells.
• Select post-transplant scenarios, such as suspected or confirmed antibody-mediated rejection, or to assess the effect of desensitization therapies on donor-specific antibody binding.

More Information about Flow Cytometry Crossmatch (FCXM) test

Other Names – Flow Crossmatch, FCXM, HLA Crossmatch, HLA Crossmatch by flowcytometry, Organ Transplantation test, Kidney transplant test, stem cell transplantation, liver transplant test, Solid Organ Transplantation,

Flow cytometry can be used to analyze different cell types. This technique can be applied to immunology to ensure that, prior to a transplant procedure, interactions between donor and recipient immune components do not cause an adverse immune reaction.

Class I and II HLA (HLA I and II) proteins are the ones involved with the immune response and transplantations. HLA I proteins are expressed on the surface of all cells. Conversely, HLA II proteins are expressed on the surface of antigen presenting cells (APCs) of the immune system, such as Dendritic cells and B-Cells.

HLA proteins are highly varied, as three genes contribute to the formation of HLA I proteins, while six genes contribute to the formation of HLA II proteins. Given that there are two distinct alleles for each gene, the possible combinations are numerous.

Flow crossmatch helps to identify the compatibility of the donor's tissue, blood, and organs with the recipient's body. The purpose of the crossmatch is to detect the presence of antibodies in the recipient against the red blood cells of the donor.