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Version: v0.1.6

Read the structured SIG

A prescription's directions can arrive as free text (<SigText>) and as a structured <Sig>. The library decodes the structured part into medication.sig, one field per dosing component, and keeps the free text verbatim on sig.sigText. The free text is the source of truth; the structured view is additive and lossy.

import { newRx, parseScript } from "@cosyte/ncpdp/script";

const xml = `<Message version="2017071"><Body><NewRx><MedicationPrescribed>
  <DrugDescription>Amoxicillin 500 MG Oral Capsule</DrugDescription>
  <Sig>
    <SigText>Take 1 capsule by mouth three times daily.</SigText>
    <DoseDeliveryMethod><Text>Take</Text><Code>419652001</Code><Qualifier>SNOMED</Qualifier></DoseDeliveryMethod>
    <DoseQuantity>1</DoseQuantity>
    <Route><Text>by mouth</Text><Code>26643006</Code><Qualifier>SNOMED</Qualifier></Route>
    <AdministrationTiming><Text>three times daily</Text></AdministrationTiming>
    <Duration><Text>10 days</Text></Duration>
  </Sig>
</MedicationPrescribed></NewRx></Body></Message>`;

const msg = parseScript(xml);
const sig = newRx(msg)?.medication?.sig;

sig?.sigText; // => "Take 1 capsule by mouth three times daily."
sig?.hasStructuredData; // => true

sig?.doseDeliveryMethod.provenance; // => "coded"
sig?.doseDeliveryMethod.code?.system; // => "SNOMED"
sig?.dose.provenance; // => "derived"
sig?.dose.text; // => "1"
sig?.route.code?.value; // => "26643006"
sig?.administrationTiming.text; // => "three times daily"

// Duration has no grounded element name, so it reads absent whatever the message carried.
sig?.duration.provenance; // => "absent"

msg.warnings.map((w) => w.code); // => ["NCPDP_SCRIPT_SIG_STRUCTURED_LOSSY"]

Each of the ten components (doseDeliveryMethod, dose, doseUnitOfMeasure, route, siteOfAdministration, administrationTiming, duration, vehicle, indication, and maximumDoseRestriction) is always present and carries a provenance:

  • coded: the element carried a <Code>; code holds the value, its qualifier verbatim, and the recognized system.
  • derived: a value was read from uncoded structure (a <Text> child or the element's own text).
  • absent: nothing was read. An absent component is never filled in from the free text.

Five components have no element name a published source grounds, so they always read absent: doseUnitOfMeasure, duration, vehicle, indication, and maximumDoseRestriction. Structured SIG decode lists the recognized names and the evidence for each.

When the dose is ambiguous​

If a dose element is present but no quantity can be read from it, the dose reads absent and the message carries NCPDP_SCRIPT_SIG_AMBIGUOUS_DOSE. The library never guesses a number.

import { newRx, parseScript } from "@cosyte/ncpdp/script";

const msg = parseScript(`<Message version="2017071"><Body><NewRx><MedicationPrescribed>
  <DrugDescription>Hydrocortisone 1 % Topical Cream</DrugDescription>
  <Sig>
    <SigText>Apply to the affected area as directed.</SigText>
    <DoseQuantity></DoseQuantity>
  </Sig>
</MedicationPrescribed></NewRx></Body></Message>`);

newRx(msg)?.medication?.sig?.dose.provenance; // => "absent"
msg.warnings.map((w) => w.code); // => ["NCPDP_SCRIPT_SIG_AMBIGUOUS_DOSE"]

When the structured dose and the free text disagree, both are returned as they arrived. Show the free text to a person; use the structured view only for what it decoded.

Reference: StructuredSig, SigField, and extractStructuredSig.

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