Scheme Description
If present before transplantation patient antibodies corresponding to donor mismatched HLA antigens can cause rejection of a donor organ. Flow cytometry crossmatching between donor and recipient is a more sensitive crossmatch technique than the complement dependant cytotoxicity test for detecting donor specific antibodies.
Purpose
To assess participants’ ability to correctly determine cell/serum flow cytometry crossmatch status. Note that the scheme is a technical assessment of flow cytometry crossmatching, and results should not be ‘interpreted’ before reporting.
The Steering Committee acknowledges that this crossmatching scheme will only partially emulate current crossmatching practice.
Samples
A total of ten blood samples and forty serum samples will be sent each year as five distributions. Each distribution will comprise of two blood samples and their two corresponding sets of four selected sera (approximately 300ml each). A serum set may include test serum replicates.
Each set of four sera must be tested against its corresponding blood sample for IgG antibody binding.
Reporting
At registration participants may opt for T-cell and/or B-cell crossmatch assessment. Participants must make a report for each cell type for which they have registered.
Test results should be reported as positive or negative compared to the local negative control. Equivocal reports will be accepted if the local criteria for a positive or negative result are not met, and equivocal is the result that would be reported clinically.
Technical issues and invalid results (e.g. control failures, replicate issues, sample quality issues) should be reported as ‘Not Tested’ with the reason stated.
Tests reported as weakly positive will be interpreted as positive for assessment purposes.
Equivocal reports will continue to contribute to the consensus result and be assessed for Scheme 2B, i.e. if 75% or more of participants agree on the positivity or negativity of a result, any laboratories reporting ‘equivocal’ will be assessed as ‘unacceptable’. Likewise, if 75% of participants report equivocal, any laboratories reporting positive or negative will be assessed as ‘unacceptable’. If the 75% consensus result is not reached when including the equivocal reports, the sample will not be assessed.
The Steering Committee acknowledge that not all laboratories have an ‘equivocal’ region and only those that would report ‘equivocal’ clinically should report this way. Technical issues and invalid results (e.g. control failures, replicate issues, sample quality issues) should be reported as ‘Not Tested’ with the reason stated. ‘Not tested’ reports will continue to be not assessed.
Participants must only use the reporting forms provided within the UK NEQAS for H&I Participant’s Portal and are required to make their report within 10 days.
Assessment
The crossmatch status of each sample is determined by at least 75% of laboratories agreeing on a positive, negative or equivocal result for each test. Crossmatching tests failing to reach the 75% consensus level will not be assessed.
UK NEQAS for H&I reserve the right to not assess a result if non-viability related performance is deemed to be an issue.
Assessment Procedure
A result in agreement with the consensus findings – Acceptable
A result not in agreement with the consensus findings – Unacceptable
Each sample not reported – with valid reason – Not Assessed
Each sample not reported / late submission of results – Unacceptable
Satisfactory Performance
Satisfactory performance is making 85% of reports in agreement with the consensus findings in a year for each cell type registered for.
Laboratories with unsatisfactory performance will receive written notification of their status and will be expected to reply to UK NEQAS for H&I detailing their corrective actions. For UK laboratories, unsatisfactory performance will be reported to UK NQAAP for Immunology. For UK laboratories, failure to reply or replies deemed unsatisfactory are likely to be further actioned by UK NQAAP for Immunology.
Information/Analysis Provided to Participants
- Anonymised summary table of all participant results, comments and methodology. Including sample assessment result (acceptable/unacceptable classification) for each participant.
- End of year summary of participant performance.
- The HLA phenotype of the donor samples and CDC detected specificities of the sera (provided on request, for indication only).