England Pathology and Laboratory Medicine (PaLM) Technical Framework
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Laboratory Testing Workflow (LTW)

The IHE PaLM Laboratory Testing Workflow (LTW) profile covers the ordering and resulting of in vitro diagnostic tests: a clinician orders a test, a specimen is collected and sent to the laboratory, the laboratory performs the test and the results are returned to the requester and stored in the patient record.

References

Process Flow

sequenceDiagram
    autonumber
    actor Clinician
    participant OP as Order Placer<br/>EPR / GP system
    participant OF as Order Filler<br/>LIMS
    participant ORT as Order Result Tracker<br/>EPR / GP system
    Clinician ->> OP: Request test (ask at order entry questions)
    OP ->> OF: OML^O21 NW / FHIR Laboratory Order (O21) [LAB-1]
    OF -->> OP: ORL^O22 OK (acknowledgement)
    Note over OP,OF: Specimen collected, labelled with the placer specimen number and sent
    OF ->> OF: Specimen received - accession number assigned
    OF ->> OP: OML^O21 SC (status changed) [LAB-2] - optional
    OF ->> OF: Test performed, results validated and authorised
    OF ->> ORT: ORU^R01 / FHIR Laboratory Result (R01) [LAB-3]
    ORT -->> OF: ACK^R01 (acknowledgement)

Ordering Patterns in England

Pattern Order Placer Order Filler Order Result Tracker Notes
Electronic order, same trust Trust EPR / order comms Trust LIMS Trust EPR All of LTW. Placer Order Number from the EPR
Electronic order from primary care GP order comms Trust or network LIMS GP clinical system Results to the GP are delivered by results distribution middleware - see Results Distribution in England
Paper request form (none) LIMS (order entered on receipt) EPR / GP system No LAB-1. The LIMS creates the order; LAB-2 may notify the Order Placer. LAB-3 results have a Filler Order Number but no Placer Order Number
Order to another laboratory Requesting LIMS Subcontractor LIMS Requesting LIMS See Inter-Laboratory Workflow

Identifiers

The workflow depends on identifiers being kept and echoed back:

Identifier Assigned by HL7 v2 FHIR
Placer Order Number Order Placer ORC-2 / OBR-2 ServiceRequest.identifier (type PLAC), DiagnosticReport.basedOn
Placer Group Number (all tests on one request form) Order Placer ORC-4 ServiceRequest.requisition
Filler Order Number (laboratory number) Order Filler ORC-3 / OBR-3 ServiceRequest.identifier (type FILL), DiagnosticReport.identifier
Placer specimen number (label) Order Placer SPM-2.1 Specimen.identifier (type PLAC)
Accession number Order Filler SPM-2.2 Specimen.accessionIdentifier
NHS Number NHS (PDS) PID-3 (NHS^NH) Patient.identifier
Hospital number (MRN) Trust PAS PID-3 (<ODS>^MR) Patient.identifier

Order Status

The Order Placer needs to know what has happened to an order. In HL7 v2 this is ORC-1 (order control) and ORC-5 (order status) in LAB-2, and OBR-25 (result status) in LAB-3. In FHIR, ServiceRequest.status and DiagnosticReport.status - see the ConceptMaps.

Stage ORC-1 / ORC-5 OBR-25 ServiceRequest.status DiagnosticReport.status
Order placed NW / - - active -
Order accepted OK / IP - active -
Specimen received SC / IP I active registered
Partial results RE / A P or A active preliminary or partial
Final results RE / CM F completed final
Corrected results RE / CM C completed corrected
Order cancelled CA, OC / CA X revoked cancelled