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Home Scheme 4A1 - HLA Typing at 1st Field Resolution

Scheme Description

Scheme 4A1 is for laboratories that undertake DNA HLA based typing at the 1st field level (formerly known as low resolution or 2-digit typing). Participants are requested to report results using the correct nomenclature https://hla.alleles.org/ . The IMGT/HLA database update (https://www.ebi.ac.uk/ipd/imgt/hla/) from the April two years prior to start of the Scheme will be taken as the ‘reference’ allele baseline for the entire year and participants will be expected to report their findings in accord with this report as a minimum (e.g. the IMGT/HLA release version (e.g. the IMGT/HLA release version 3.40 (2020-04) will be used throughout 2022-23).

 

Purpose

To assess participants’ ability to correctly determine HLA alleles at the 1st field level.

This scheme can be used by those laboratories that provide HLA typing for deceased donor characterisation.  There is also the option to include Scheme 4A1i registration to verify the correct interpretation of Scheme 4A1 DNA based typing results to the ‘split’ HLA specificity level

 

Samples

A total of ten blood samples will be sent each year as three distributions of three/four blood samples.

 

Reporting

Participants may register for any of the following: HLA-A, B, C, DRB1, DRB3, DRB4, DRB5, DQA1, DQB1, and DPA1 for 1st field assessment, or ‘presence of’ assessment for DRB3, DRB4 and, DRB5. DPA1 results will be assessed if sufficient results are received.

Participants may register for DPB1 low-intermediate resolution assessment.  This is for laboratories that type clinically at a low-intermediate resolution e.g. PCR SSP or SSO results for solid organ transplant antibody analysis, where the results may not meet the minimum typing requirements of Scheme 4A2 – 2nd field resolution typing (i.e. unable to resolve all ambiguities resulting from polymorphisms located within exon 2). Scheme 4A1 DPB1 results will be assessed against a reference DPB1 type.

There are no minimum typing requirements for DPB1 in Scheme 4A1, so laboratories are able to report the DPB1 results at the resolution that is applicable to their clinical need. This includes reporting strings of DPB1 alleles that differ at the first field. Assessment is performed by comparing the participant DPB1 result to the reference DPB1 type; acceptable results will include the reference allele in the report. Laboratories performing ‘high resolution’ DPB1 typing would still be expected to participate in Scheme 4A2.

Participants must only use the reporting forms provided within the UK NEQAS for H&I Participant’s Portal and return results within 2 weeks.

 

Assessment

Participating laboratories will be assessed on the loci they designate at registration.

The consensus full HLA genotype is determined by at least 75% of laboratories agreeing each allele. A “blank” forms part of the assessment if at least 75% of laboratories report a single allele at a locus.

A reference result will be used for DPB1 assessment and for other results failing to reach the 75% consensus level.

Participants will only be assessed on those alleles that appear in the IMGT/HLA database update from the April two years prior to start of the Scheme (e.g. the IMGT/HLA release version 3.32.0 (2018-04) will be used throughout 2021-22).

 

Assessment Procedure

Each full HLA genotype in agreement with the consensus/reference type – Acceptable

Each full HLA genotype not in agreement with the consensus/reference type – Unacceptable

Each sample not reported – with valid reason – Not Assessed

Each sample not reported / late submission – Unacceptable

 

Satisfactory Performance

Satisfactory performance is obtaining nine or more full HLA genotypes in agreement with the consensus/reference genotypes in a year.

 

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 (see section 10.6). 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.