HL7 v2 vs FHIR R4 for laboratory integration in 2026
Most lab-to-EMR integrations in 2026 still use HL7 v2. That sentence is mildly controversial — every industry conference, every vendor demo, every standards-body roadmap names FHIR R4 as "the modern standard". The roadmap is real; the production reality is that the majority of clinical-lab traffic still moves over HL7 v2 messages because Epic, Cerner, Meditech, Allscripts, athenahealth, and eClinicalWorks all support v2 as their primary integration mode, and the lab on the other end already speaks v2. FHIR R4 adoption is climbing meaningfully — most major EMRs now expose FHIR endpoints — but the bulk of orders and results still cross the wire as ORM^O01 and ORU^R01 messages. This post is the side-by-side comparison: wire format, message types, transport, tooling, real-world coverage, and the migration trade-offs every lab eventually faces.