Imperial Collage Healthcare

HLA crossmatch (wet crossmatch)

Test Background

There are two crossmatch tests that are used to assess patient and donor compatibility. These are the
complement dependent cytotoxicity (CDC) and flow cytometry crossmatches (FCXM).

CDC detects IgG and IgM complement fixing antibodies, with IgG complement fixing antibodies being particularly likely to cause antibody-mediated rejection.

The FCXM detects both complement and non-complement fixing antibodies and is a more sensitive assay than the CDC test, ensuring low level antibodies directed  towards donor HLA are detected.

Clinical Indications

Preformed IgG, or occasionally IgM antibodies, in the recipient, directed against donor HLA antigens, are a cause of hyperacute or accelerated allograft rejection. HLA crossmatching tests recipients’ serum for the presence of pre-formed anti-donor antibodies which may represent an additional risk or contraindication to transplantation in solid organ grafts.

Crossmatching tests, in particular the CDC crossmatching, are particularly relevant for the prevention of hyperacute rejection of the graft. The crossmatching tests alongside HLA antibody testing allows risk of rejection to be stratified and aids in the assessment of suitability of donor recipient pairs.

The Flow crossmatch test is an integral part of donor selection procedures and ensures that low level antibodies directed towards donor HLA are also detected.

Reference Range

Sample Required
Donor samples: 40ml EDTA (lavender top) Recipient samples: 10 mL Clotted Sample (red top) + 20ml EDTA (lavender top) if HLA typing is also required.


ALL samples must be <24 hours old (testing requires viable cells)

The laboratory is accredited for the flow cytometry crossmatch test by the European Federation of Immunogenetics (EFI), however UKAS accreditation for the most recently acquired analyser is pending.

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