Synthea (MITRE's open-source patient simulator) is the default source of synthetic FHIR data. We generated two patients (java -jar synthea-with-dependencies.jar -p 2 -s 4242 Massachusetts) and loaded them into Anpheros, the FHIR backend I work on. The first bundle had 221 entries.

What did not fit: 39 entries of types the server does not store — Claim (13), ExplanationOfBenefit (13), SupplyDelivery (9), Device (2), ImagingStudy (1), MedicationRequest (1). Synthea models US billing in detail; a clinical record usually doesn't need it.

The loader asks the server which types it supports and posts the rest as one transaction:

import { readFile } from 'node:fs/promises'; import { Anpheros, apiKey } from '@anpheros/sdk'; const anpheros = new Anpheros({ auth: apiKey(process.env.ANPHEROS_KEY!) }); // a sandbox key, sk_test_… const SUPPORTED = new Set(((await anpheros.fhir.metadata()) as any).rest[0].resource.map((r: any) => r.type)); const bundle = JSON.parse(await readFile(process.argv[2], 'utf8')); // one Synthea patient file const kept = bundle.entry.filter((e: any) => SUPPORTED.has(e.resource.resourceType)); const out: any = await anpheros.fhir.transaction({ ...bundle, entry: kept } as any); console.log('created', out.entry.length);

182 resources were created in one transaction, urn:uuid references resolved, and the patient's International Patient Summary came out with 15 problems, 6 immunizations, 15 results and 28 vital signs.

Three things to watch if you do the same with any server:

  • Conditional references. Synthea points to practitioners and organisations as Practitioner?identifier=…. Servers differ: ours stored them as written and did not resolve them. Check yours before following those links.
  • Removed is not converted. Dropping MedicationRequest means the medication disappears. Convert it to MedicationStatement first if you need it.
  • Names with numbers (Marcelo725 Gulgowski816) are deliberate, so no one mistakes synthetic people for real ones.

Full guide, including when to use Synthea vs hand-made personas and what good test data must contain: Synthetic patient data for testing.