If present at a high concentration, patient antibodies corresponding to donor mismatched HLA antigens can cause immediate and irreversible rejection of a transplanted organ. Performing a prospective complement dependant cytotoxicity (CDC) crossmatch between donor and recipient can prevent hyperacute rejection. Participants may register to test peripheral blood lymphocytes (PBL) and/or T-cells and/or B-cells, with and/or without dithiothreitol (DTT) treatment of sera, according to their local method and practice.
To assess participants’ ability to correctly determine cell/serum cytotoxic crossmatch status. Note that the scheme is a technical assessment of cytotoxic crossmatching, and results should not be ‘interpreted’ before reporting.
The Steering Committee acknowledges that this crossmatching scheme will only partially emulate current crossmatching practice.
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 150ml each). A serum set may include test serum replicates.
Each set of four sera must be tested against its corresponding blood sample.
At registration participants may opt for assessment of the following cell/DTT combinations according to their local practice;
Peripheral Blood Lymphocytes with DTT Peripheral Blood Lymphocytes without DTT
T-Cell with DTT T-Cell without DTT
B-Cells with DTT B-Cells without DTT
Test results should be reported as positive or negative using established local criteria. Participants must make a report for each cell/DTT category for which they have registered.
Tests reported as weakly positive will be interpreted as positive for assessment purposes.
Equivocal reports are not accepted for Scheme 2A. Technical issues and invalid results (e.g. control failures, replicate issues, sample quality issues) should be reported as ‘Not Tested’ with the reason stated. The Steering Committee feel that there are no circumstances where a result is undetermined or equivocal for cytotoxic crossmatching, and these reports will no longer be accepted for Scheme 2A.
Participants are requested to report reaction strength, using their own scoring system, to enable comparison between laboratories.
Technical issues and invalid results (e.g. control failures, replicate issues, sample quality issues) should be reported as ‘Not Tested’ with the reason stated. Equivocal reports are not accepted for Scheme 2A.
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.
The crossmatch status of each sample is determined by at least 75% of laboratories agreeing on the positivity or negativity of each cell/DTT combination. Crossmatching tests failing to reach the 75% consensus level will not be assessed. All PBL, T-cell, B-cell results with/without DTT treatment of sera are considered independently.
UK NEQAS for H&I reserve the right to not assess a result if non-viability related performance is deemed to be an issue.
A result in agreement with the consensus findings – Acceptable
A result not in agreement with the consensus findings – Unacceptable
Each sample/registered category not reported – with valid reason- with valid reason – Not Assessed
Each sample/registered category not reported / late submission of results – Unacceptable
Satisfactory performance is making 85% of reports in agreement with the consensus findings in a year for each cell/DTT combination 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).