NHS North West Genomics - Local Development build (v2.2.0) built by the FHIR (HL7® FHIR® Standard) Build Tools. See the Directory of published versions

Use Case: Histocompatibility and Immunogenetics (Clatterbridge to Histotrac)

Clatterbridge Chimerism Testing - process overview.

References

1. HL7 FHIR Genomics Reporting - Histocompatibility and Immunogenetic Reporting (a dependency of this IG)
2. Genomic Test Order - Order Entry Questions
3. HL7 v2 OML_O21
4. Original Histotrac ORM^O01 order (HLA Antibody Screening) - histotrac-MFT-HLA.txt
5. Original Histotrac ORM^O01 order (Chimerism Testing) - histotrac-MFT-chimerism.txt
6. NHSBT H&I Haematopoietic Stem Cell Transplantation (Recipients & Donors) request form (FRM1010) - NHSBT's published PDF
7. NHSBT H&I Organ Transplant (Patients and Donors) request form (FRM1008) - NHSBT's published PDF

Clinical Pathway Overview

What is being tested

The end-to-end clinical journey

1. Patient identified - the transplant team, or a renal/haematology clinician, identifies a transplant candidate needing HLA compatibility screening, or a post-transplant patient needing chimerism monitoring.
2. Sample taken - a blood sample is collected.
3. Order sent - the referring clinician's EPR sends the order to the testing laboratory. (This is the Order Placer → Order Filler step in the technical process below.)
4. Testing performed - HLA antibody screening or STR-based chimerism analysis is carried out.
5. Result reported - the report reaches the referring clinician/transplant team.
6. Clinical decision - the transplant team uses the HLA result to assess compatibility/rejection risk before transplant, or uses the chimerism trend to decide whether to adjust immunosuppression or investigate possible graft failure/relapse.

flowchart LR
    A[Transplant candidate<br/>or recipient identified] --> B[Blood sample taken]
    B --> C[Order sent to<br/>testing laboratory]
    C --> D[HLA screening or<br/>chimerism analysis]
    D --> E[Result reported to<br/>transplant team]
    E --> F[Compatibility /<br/>engraftment decision]

Why this matters for developers

• HLA screening data (HLA Type, Patient type, Organ, Specimen source) currently arrives as free-text NTE segments on the order - see Ask At Order Entry Questions for how these map onto structured Ask At Order Entry answers.
• Chimerism results are currently unstructured local OBX/NTE codes (STR/IM/RANGE/CV/EXT/PURE/POST/DTP/DID) - see Chimerism Testing Result Panel (Future?) for the proposed structured data model.
• The interim manual order-entry step via HODS is a temporary workaround while electronic ordering/reporting is re-established - not the target state.

Actors

Transactions

Current Process

Historical Background (Original Process, now retired)

Chimerism testing at Clatterbridge originally worked as follows:

1. Clatterbridge (Meditech EPR) sent an ORM_O01 message to the Clatterbridge TIE, which forwarded it to the LUFT TIE, which in turn forwarded it to the iLab LIMS.
2. Once testing was complete, Clatterbridge (Meditech EPR) received a structured ORU_R01 message back from iLab, routed via the LUFT TIE and then the Clatterbridge TIE.

This closed-loop process corresponds to the IHE Laboratory Testing Workflow.

sequenceDiagram
    participant CM as Clatterbridge Meditech (EPR)<br/>Order Placer
    participant CTIE as Clatterbridge TIE<br/>Intermediary
    participant LTIE as LUFT TIE<br/>Intermediary
    participant iLab as iLab LIMS<br/>Order Filler

     CM->>CTIE: ORM_O01
    CTIE->>LTIE: ORM_O01
    LTIE->>iLab: ORM_O01
    Note over iLab: Testing performed
    iLab->>LTIE: ORU_R01
    LTIE->>CTIE: ORU_R01
    CTIE->>CM: ORU_R01

Current State (Interim Process)

Following organisational restructuring, testing was transferred to North West Genomics (hosted by Manchester Foundation Trust). As part of this change, Histotrac replaced iLab as the testing system. The electronic exchange of results was discontinued, and HODS was adopted as an interim order comms system for Clatterbridge users to submit lab orders.

sequenceDiagram
    participant User as Clatterbridge User<br/>Order Placer (interim, manual)
    participant HODS as HODS (Order Comms)<br/>Order Placer (interim, manual)
    participant Histotrac as Histotrac (NW Genomics / MFT)<br/>Order Filler

    User->>HODS: Manual order entry
    Note over HODS,Histotrac: No electronic order exchange
    Note over Histotrac: Testing performed
    Note over HODS,Histotrac: No electronic result exchange
    Note over User: Results retrieved outside EPR

Future Process

The current project aims to re-establish electronic ordering and reporting. The new message flows are:

• Clatterbridge Meditech → Clatterbridge TIE → NW Genomics Regional Integration Engine (RIE) → Histotrac — still an ORM_O01 message, though no longer classified as LAB-1 due to the involvement of a regional integration engine.
• Histotrac → NW Genomics Regional Integration Engine → Clatterbridge TIE → Clatterbridge Meditech — still an ORU_R01 message, classified as LAB-3. See Regional Integration Engine (RIE) - Report Process for how the RIE validates, enriches and routes this report before it reaches Clatterbridge.

Communication between the Clatterbridge TIE and the NW RIE will follow the NW Genomics HL7 v2 standard — a data contract shared across NHS Trusts in the North West. NW Genomics will not build Trust-specific transformations; instead, the standard is designed collectively to meet the needs of all participating NHS organisations.

The data contract (North West Genomics HL7 v2 standard) is based on a union of:

• NHS England HL7 v2 ADT
• DHCW (NHS Wales) HL7 v2 ORU
• NHS Data Model and Dictionary

HL7 v2.5.1 was chosen as the version for the standard, as it uses a model compatible with HL7 FHIR and also aligns with the version used by NHS Wales (DHCW).

Note: The Data Contract only exists between NHS Trusts and NW Genomics — it does not apply to local integrations with EPR or LIMS systems. See also the Canonical Data Model pattern.

The NW Genomics RIE will handle the necessary transformations between the NW HL7 standard and Histotrac's HL7 v2 format.

sequenceDiagram
    participant CM as Clatterbridge Meditech (EPR)<br/>Order Placer
    participant CTIE as Clatterbridge TIE<br/>Intermediary
    participant RIE as NW Genomics RIE<br/>Intermediary
    participant Histotrac as Histotrac<br/>Order Filler

    CM->>CTIE: ORM_O01
    Note over CTIE,RIE: Data contract: NW Genomics HL7 v2 standard
    CTIE->>RIE: ORM_O01 (NW Genomics HL7 v2 standard - LAB-1)
    RIE->>Histotrac: ORM_O01 (transformed to Histotrac HL7 v2)
    Note over Histotrac: Testing performed
    Histotrac->>RIE: ORU_R01 (Histotrac HL7 v2)
    Note over CTIE,RIE: Data contract: NW Genomics HL7 v2 standard
    RIE->>CTIE: ORU_R01 (NW Genomics HL7 v2 standard - LAB-3)
    CTIE->>CM: ORU_R01

    Note over RIE,Histotrac: RIE performs HL7 transformation

This separation of responsibilities enables modular delivery. For example, the reporting flow from NW Genomics to Clatterbridge can be implemented and tested independently — which is useful for validating the firewall between NW Genomics (hosted by MFT) and Clatterbridge.

This modularity also allows components to be reused across other projects. For instance, the iGene Genomic Reports feed into the RIE for Clatterbridge has already been built, and — being nearly identical to the Histotrac reports flow — can be used both to test the firewall and to inform development of the NW Genomics RIE-to-Clatterbridge reports feed. Genomic Reports from iGene to Clatterbridge follow exactly the same Report Process as the Histotrac reports flow above - only the originating LIMS differs.

sequenceDiagram
    participant CM as Clatterbridge Meditech (EPR)<br/>Order Placer
    participant CTIE as Clatterbridge TIE<br/>Intermediary
    participant RIE as NW Genomics RIE<br/>Intermediary
    participant iGene as iGene<br/>Order Filler

    iGene->>RIE: ORU_R01 (iGene format)
    RIE->>CTIE: ORU_R01 (NW Genomics HL7 v2 standard - LAB-3)
    CTIE->>CM: ORU_R01 

    Note over CTIE,RIE: Used to test firewall and inform RIE-to-Clatterbridge reports feed

Outstanding Issues

1. It has not yet been decided, from a business process perspective, whether HODS will be replaced as the order comms system. It is desired that orders originating from Meditech are reinstated.
2. The full narrative report will be in PDF format (this was not present in the original process), the provisional UK SNOMED CT of 909871000000100 Histocompatibility and immunogenetics will be used (this is from NHS Scotland standards).
3. NW Genomics would prefer the order to use OML_O21 rather than ORM_O01, to future-proof the exchange - specifically so it can carry an SPM (Specimen) segment. See Specimen - Domain Archetype for the specimen fields this would carry; the main fields needed here are Specimen ID and Specimen Type.
4. Decided: patient_test/request_details items map to ServiceRequest.orderDetail, not ServiceRequest.code. HLATestsTransplantAskAtOrderEntry declares derivedFrom Genomic Test Order with derivation type extends, and its patient_test item ("Patient Test(s)") used to map to ServiceRequest.code - the same single-cardinality FHIR element the base Questionnaire's own Test Code item also maps to, with no enableWhen linking the two. The same conflict applied to ChimerismTestAdditionalAskAtOrderQuestions's own patient_test item. Both, plus Organ Transplant (Patients and Donors)'s request_details item, are now remapped to ServiceRequest.orderDetail, which is repeating and intended for exactly this kind of further order qualifier, resolving the conflict.
5. No Test Category or Test Code exists for Histocompatibility and Immunogenetics in the base Questionnaire. The base's Test Category item (OrderCategory) only offers Rare and Inherited Disease, Storage of Specimen, Pre-Natal, Haemoglobinopathy and Cancer Genetic Testing - there is no Histocompatibility/Immunogenetics category, so none of the base's three enableWhen-gated Test Code branches can ever fire for this order type. This matches the Patient Test(s) item's own open question: no NHS England Genomic Test Directory code was found for H&I test names, since H&I is not part of that directory.
6. TODO: decide whether the Patient Test(s) items should move from local codes to a national code system. Both AskAtOrderEntry Questionnaires' Patient Test(s) items are currently coded locally against the NWGMSA CodeSystem (five HLA test values, five Chimerism test values), since no confirmed national binding was found during initial research - see each Questionnaire's own patient_test-reference design note (HLA Tests - Transplant, Chimerism Test Additional Ask At Order Entry Questions) for candidate LOINC panels already identified for the HLA side. Now that there are two separate local code lists doing the same job for two different test families, it's worth a deliberate decision rather than leaving both as local by default: confirm whether a national code system (LOINC, SNOMED CT, or an NHSBT-published binding once one exists) should replace either or both lists, or whether local coding is the right long-term answer here because H&I sits outside NHS England's Genomic Test Directory.
7. Should Clatterbridge order against national test codes rather than Histotrac's local ones, with the RIE doing the code translation? Unlike the local NWGMSA codes discussed above, NHS England Digital Genomic Test Services ($DGTS) already publishes national TP (Test Package)/GT (Genomic/Genetic Test) codes for other genomic test families. If Clatterbridge's own orders used $DGTS codes rather than Histotrac's local test codes, the NW Genomics Regional Integration Engine (RIE) - which already sits between Clatterbridge and Histotrac on both the order and report path (see Future Process above) - could map national code to local Histotrac code as part of the same transformation it already performs, rather than Clatterbridge needing to know Histotrac's local coding at all. Beyond H&I, this would also mean Clatterbridge is already speaking the same national test-code language other genomic test families (Rare Disease, Cancer) use, making it materially easier to onboard Clatterbridge onto those via iGene/StarLIMS LIMS in future, rather than each new test family needing its own bespoke local-code agreement with Clatterbridge.

Data Models

Ask At Order Entry Questions

Histocompatibility and Immunogenetics orders use the same common core order form as every other order/test type (HL7 v2 OML_O21 / FHIR Message O21), with their own Ask At Order Entry Questionnaire per Hive order screen for the questions specific to that screen - see Order Entry Questions. There are two such screens/Questionnaires: HLA Tests - Transplant below, and Chimerism Testing Ask At Order Entry further down the page. Two further Questionnaires model NHSBT's own national paper request forms directly rather than a Hive order screen - Organ Transplant (Patients and Donors), the national form underlying HLA Tests - Transplant above, and HSCT Recipients and Donors Ask At Order Entry - see each section for how it relates to the Hive-derived Questionnaires above.

HLA Tests - Transplant Ask At Order Entry

These questions were extracted from a live Histotrac ORM^O01 order for an HLA Antibody Screening (Transplant) test: five NTE segments, each carrying comment type OSQ and a local Label:->Value convention in NTE-3:

NTE|1||Patient Test(s):->HLA ANTIBODY SCREENING (TRANSPLANT)|OSQ
NTE|2||HLA Type:->Patient|OSQ
NTE|3||Patient type:->Renal|OSQ
NTE|4||Organ:->Kidney|OSQ
NTE|5||Specimen source->Blood|OSQ

Field mapping: HLA Tests NTE → FHIR

Organ Transplant (Patients and Donors) Ask At Order Entry

NHSBT's own national H&I Organ Transplant (Patients and Donors) paper request form (FRM1008) - see NHSBT's published form. This is the national form the HLA Tests - Transplant Questionnaire's own design notes above already identify as FRM1008, but that Questionnaire reflects Hive's own narrower order-entry UI (Patient Type: Stem cell/Renal/Thoracic; Organ: Kidney/Pancreas/Islets/Simultaneous Pancreas-Kidney/Simultaneous Islet-Kidney) rather than this form's own Category (Patient - Renal/Patient - Non-Renal/Donor, each with its own sub-checklist) and Request details (HLA type, HLA specific antibodies, Live donor crossmatch, Auto crossmatch) sections. Modelled directly from the paper form, the same approach as HSCT Recipients and Donors below, and reusing that Questionnaire's Role (Patient/Family Member - Potential Donor) pattern for its own "Complete for new patients only" vs "Complete for Family Member / Potential Donor" sections. Request details maps to ServiceRequest.orderDetail, not ServiceRequest.code, the same reasoning as HLA Tests - Transplant's Patient Test(s) item above - see Outstanding Issues item 4.

Chimerism Testing Ask At Order Entry

These questions were extracted from a live Histotrac ORM^O01 order for a Chimerism Testing (Performable) test - see histotrac-MFT-chimerism.txt. Unlike HLA Tests - Transplant above, this order carries only two NTE segments, and in the reverse order (Specimen Source before Patient Test(s)):

NTE|1||Specimen Source :->Blood (PB)|OSQ
NTE|2||Patient Test(s):->Chimerism Peripheral Blood (PB)|OSQ

Field mapping: Chimerism NTE → FHIR

This is the order-entry counterpart to the Chimerism Testing Result Panel below - this section covers what is asked when the test is ordered, that section covers the structured result payload once testing is complete.

HSCT Recipients and Donors Ask At Order Entry

Unlike the two Hive-derived Questionnaires above, this one models NHS Blood and Transplant's (NHSBT) own national H&I Haematopoietic Stem Cell Transplantation (Recipients & Donors) paper request form (FRM1010) directly - see NHSBT's published form. No live system message for this form has been sourced, so field mappings are this IG's own best-effort candidates rather than confirmed against a live order.

The form's own HLA Typing, Chimerism Analysis and HLA Specific Antibody Testing checkboxes overlap with, but are coarser than, the Patient Test(s) checklists already modelled on HLA Tests - Transplant and Chimerism Testing Ask At Order Entry above - this form only distinguishes HLA Class I vs Class I+II, and Chimerism Total/Whole Blood vs Lineage specific, not those Questionnaires' finer-grained checklists. A separate form must be completed for each individual (patient or family member/potential donor) per NHSBT's own instruction - modelled as a Role choice with enableWhen-conditioned items, since FHIR Questionnaire has no native "delete as applicable" concept.

Chimerism Testing Result Panel (Future?)

The proposed payload is unstructured. The original payload contained structured data. See HL7 FHIR Genomics Reporting - Histocompatibility and Immunogenetic Reporting (a dependency of this IG) for the international FHIR pattern this could structure onto - a DiagnosticReport (Genomic Report) referencing per-gene Genotype Observations, each of which can reference Haplotype Observations and the MolecularSequence evidence behind them. That page profiles HLA allele genotyping specifically, though, not STR-based chimerism analysis - most rows below have no direct fit and are noted as such rather than forced onto it.

Examples

Security Considerations

Includes:

• OAuth2 Standard for Authorisation
  • including use of JWT access tokens and future support for SMART-on-FHIR Scopes
• FHIR AuditEvent/IHE BALP for Audit Logging
• TLS for Transport Security/Encryption

Developer Guides

• 10 - Histocompatibility and Immunogenetics: HL7 v2 to and from the NW Standard - hand-builds the field-level conversion a Trust Integration Engine (TIE) does to turn Clatterbridge's Meditech-originated order into the shared NW HL7 v2 standard

See Developer Guides for the full notebook series.