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Narrative Reports and Discrete Results

Pathology reports come in two broad kinds. Which kind a report is decides how easily it fits a FHIR Document. A FHIR Document requires a Composition with human-readable narrative, so the kind that fits worst is the discrete result (FBC, HbA1c, U&E) - the opposite of what is often assumed.

Terms

Where a single word is wanted on each side, this guide uses report for the narrative kind and result for the discrete kind. The NHS and RCPath split between cellular pathology and blood sciences follows the same line roughly, but not exactly: microbiology, genomics and interpretive comments in blood sciences fall on either side.

In messaging the difference shows as:

Which Reports Are Usually Narrative

Usually narrative (text with headings, or PDF):

• Histopathology / surgical pathology - clinical details, macroscopic, microscopic, conclusion. Cancer resections follow the RCPath datasets (synoptic), but are often still sent as text with a table inside it
• Cytopathology - non-gynae cytology (fluids, FNA); cervical screening is more coded but carries text
• Post-mortem reports
• Haematology interpretation - blood film comments, bone marrow aspirate and trephine, flow cytometry immunophenotyping
• Genomic and molecular pathology - often PDF (Genomic Laboratory Hub reports, NGS panels, whole genome sequencing, variant interpretation)
• Cytogenetics - karyotype (ISCN string) and FISH, with interpretation
• Specialist and referral tests - results from reference laboratories, often PDFs attached by the local LIMS rather than re-keyed
• Microbiology - in part: organism and sensitivities can be discrete, but culture narratives, clinical advice, TB and mycology reports are text
• Interpretive comments on discrete results - dynamic function tests, protein electrophoresis / paraprotein, thrombophilia screens

Usually discrete:

• routine clinical biochemistry (U&E, LFT, lipids, HbA1c)
• routine haematology (FBC, coagulation)
• most immunoassays and serology with numeric or qualitative results

Cellular pathology is out of scope of this guide - see Cancer Pathology Report; genomics is covered by the NW GMSA FHIR IG. They are listed here because the distinction matters for the specialisms that are in scope (see Specialisms), which are mostly discrete with some narrative.

Report Patterns

Each diagram shows the FHIR resources, the HL7 v2 segment each one comes from, and the element that links them.

Discrete Results

For FHIR Messages and Resource Access. A report is one DiagnosticReport (the OBRs sharing OBR-3). Each DiagnosticReport.result is either a panel - a test group, one OBR with several OBX, as an organizer Observation whose hasMember are the results - or a single result (an OBR with one OBX).

Panel - for example the full blood count:

flowchart LR
    DR["DiagnosticReport<br/>ORU_R01 report<br/>OBR-3, OBR-22, OBR-25"]
    P["Observation - panel<br/>test group (organizer)<br/>OBR-4 e.g. FBC"]
    R1["Observation - result<br/>OBX e.g. Haemoglobin"]
    R2["Observation - result<br/>OBX e.g. White cell count"]
    R3["Observation - result<br/>OBX ..."]
    DR -- result --> P
    P -- hasMember --> R1
    P -- hasMember --> R2
    P -- hasMember --> R3

Single result - for example HbA1c:

flowchart LR
    DR["DiagnosticReport<br/>ORU_R01 report<br/>OBR-3, OBR-22, OBR-25"]
    R["Observation - result<br/>OBX e.g. HbA1c<br/>(OBR-4 is the same test)"]
    DR -- result --> R

Both patterns can be mixed in one report - for example lipids (a panel) and HbA1c (a single result) from one request:

flowchart LR
    DR["DiagnosticReport<br/>OBRs sharing OBR-3"]
    P["Observation - panel<br/>OBR 1: Serum lipids"]
    R1["Observation - result<br/>OBX Cholesterol"]
    R2["Observation - result<br/>OBX HDL cholesterol"]
    S["Observation - result<br/>OBR 2 / OBX HbA1c"]
    DR -- result --> P
    P -- hasMember --> R1
    P -- hasMember --> R2
    DR -- result --> S

Examples: FBC (panel), HbA1c (single result), LFT and U&E (two panels), Lipids and HbA1c (mixed) - see NHS England Examples.

Narrative Reports

Rendered report (PDF) - an OBX of type ED (Base64 PDF) or RP (a link) becomes a DocumentReference and a Binary (the OBX type ED convention). The DiagnosticReport stays the parent: it lists the DocumentReference among its results, and the DocumentReference points to the PDF:

flowchart LR
    DR["DiagnosticReport<br/>ORU_R01 report"]
    DOC["DocumentReference<br/>OBX type ED / RP<br/>OBX-3 document type"]
    BIN["Binary<br/>the PDF<br/>OBX-5 ED-5 Base64 data"]
    DR -- "result<br/>(R4: media.link)" --> DOC
    DOC -- content.attachment.url --> BIN

A rendered report is normally exchanged in one of two ways (see the general rule above):

• Document Exchange (IHE MHD / XDS) - focused on the DocumentReference: the PDF is published and found as a document, through its metadata (type, date, author, patient), and the DiagnosticReport is optional context
• Resource Access (IPA / QEDm), or a FHIR Message - focused on the DiagnosticReport: the report is queried or sent as a result, and the PDF is reached from it (presentedForm / the DocumentReference)

Text report in a FHIR Message or Resource Access - the text is in OBX of type ST / FT (or TX lines), and becomes a result whose value is the text - for example the unstructured GTT and urine MCS reports:

flowchart LR
    DR["DiagnosticReport<br/>ORU_R01 report"]
    R["Observation - result<br/>valueString<br/>OBX type ST / FT<br/>(line breaks become new lines)"]
    DR -- result --> R

Text report in a FHIR Document (Document Exchange) - the link is simply Composition to section to narrative. The OBX of type ST / FT is used to create the section: OBX-3 gives section.code (and title), and OBX-5 (with \.br\ as line breaks) gives section.text:

flowchart LR
    C["Composition<br/>FHIR Document header<br/>Composition.text"]
    S["section<br/>section.code from OBX-3"]
    N["Narrative<br/>section.text<br/>from OBX-5 (ST / FT)"]
    C -- section --> S
    S -- text --> N

Examples: GTT and urine MCS (FHIR Messages), and their FHIR Documents (GTT, urine MCS).

Discrete Results in a FHIR Document (Document Exchange)

A Composition can also carry discrete results. The Composition is the parent: the DiagnosticReport is an entry in a section, and links on to its panels and results as in the FHIR Message. The Observations are also entries in the sections: a section entry can be the panel Observation (usually one section per panel, as in the NHS England examples) or an individual result directly. The section's narrative is generated from those results - see Why Discrete Results Are Harder to Send as a FHIR Document:

flowchart LR
    C["Composition<br/>FHIR Document header<br/>Composition.text"]
    S["section<br/>section.text = generated<br/>table of results"]
    DR["DiagnosticReport<br/>ORU_R01 report"]
    P["Observation - panel<br/>OBR-4"]
    R1["Observation - result<br/>OBX"]
    R2["Observation - result<br/>OBX"]
    C -- section --> S
    S -- entry --> DR
    S -- entry --> P
    S -- entry --> R2
    DR -- result --> P
    P -- hasMember --> R1
    P -- hasMember --> R2

Examples: FBC, LFT and U&E and Lipids and HbA1c (FHIR Documents).

Why Discrete Results Are Harder to Send as a FHIR Document

A FHIR Document is a Bundle of type document whose first entry is a Composition. The NHS England Pathology Laboratory Reporting API requires one, and HL7 Europe Composition-eu-lab (the parent of the Laboratory Report Composition) requires at least one section and makes section.text mandatory (1..1). The narrative is the attested, human-readable content of the document (Human Readable and Computer Processable).

For a narrative report this fits naturally: the laboratory already wrote the narrative. Its headings (macroscopic, microscopic, conclusion) become sections, the authorised text becomes section.text, and what is coded is added alongside it. The document is a wrapper for content that already exists.

For a discrete result there is usually nothing to put there:

• No narrative exists. An FBC or HbA1c result is a set of values, not text; the ORU^R01 has no text form of it beyond a few NTE comments. The sender SHALL make one to meet section.text 1..1
• The narrative is generated, not authored. The sending system (usually the order comms system, not the LIMS) creates a table from the coded data. It SHALL agree with the coded data - a value rounded differently, or a lost flag or comment, is a clinical safety issue - so it has to be generated from the resources, and tested as clinical content
• Who attests it is unclear. The laboratory authorised the values, not the rendered table. The document's attested content is something no one in the laboratory has seen (Open - how this is covered in the clinical safety case, DCB0129 / DCB0160)
• The sections have to be invented. A narrative report has headings; discrete results only have test groups (OBR), so each test group becomes a section, with the test group code as section.code
• It is extra work for no new information. The receiver (a GP system) files and displays the coded Observations, as it does today from EDIFACT; the narrative adds a second copy that must be kept in step. The NHS England examples leave section.text as empty (text.status = empty), which shows the difficulty
• It does not suit other routes. HL7 v2 ORU^R01 and FHIR Messages carry discrete results without a Composition. HL7 Europe DiagnosticReport-eu-lab requires the DiagnosticReport.composition extension, which is why this guide's Laboratory Report is derived from EU Core instead (see Why These Parents)

In short, the FHIR Document model suits narrative reports, where a document already exists. For discrete results it adds an artificial document that has to be generated. For how to generate the narrative safely from an ORU^R01, see What it means when transforming ORU^R01.

References

• HL7 Europe Health Data API (1.0.0-ballot) - Document Exchange, Resource Access, FHIR Documents and Resources
• FHIR R4 Documents and Narrative
• HL7 Europe Laboratory Report - Composition
• Royal College of Pathologists - Cancer datasets and tissue pathways
• NHS England Pathology FHIR Implementation Guide