CDS Hooks

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Source: HL7 System: https://cds-hooks.org Code: CDS Hooks Reviewed: 19/12/2025 License: CC-BY-4.0

CDS Hooks

One-sentence definition: CDS Hooks is an HL7 standard that defines how EHRs can call external clinical decision support services at specific workflow moments — such as when a medication is ordered or a patient record is opened — and display the service’s guidance as cards within the EHR interface.

Full Definition

Clinical decision support has traditionally been embedded inside EHRs as proprietary logic that is difficult to update or replace. CDS Hooks decouples the CDS logic from the EHR by defining a vendor-neutral protocol: the EHR fires a standardized HTTP request at a specific hook event (e.g., order-sign, patient-view, encounter-start), an external CDS service receives that request with relevant patient context, and responds with cards — structured suggestions, information notices, or smart links — that the EHR renders in its UI.

The payload the EHR sends to the CDS service includes the hook name, the current EHR context (such as the patient ID, the draft order, or the encounter), and optionally prefetched FHIR resources the service declared it needs. The service responds with cards that may contain advisory text, suggested actions (like an alternative medication), or links to launch a SMART app. The EHR decides how to present the cards; the CDS service has no direct control over EHR UI rendering.

CDS Hooks is maintained as an HL7 standard and is referenced in the Da Vinci Coverage Requirements Discovery (CRD) IG as the mechanism for surfacing prior authorization requirements at order time.

Context and Usage

Where This Term Appears

  • Prior authorization workflows: The Da Vinci CRD IG uses order-sign hooks to surface coverage requirements before an order is submitted
  • Drug interaction alerts: EHRs can delegate formulary and interaction checking to external CDS services via CDS Hooks
  • Guideline-based reminders: Population health tools use patient-view hooks to surface care gap alerts when a chart is opened
  • SMART app launch: CDS cards can include a link that launches a SMART on FHIR app with patient context pre-loaded

Common Usage Examples

In conversation: “The CRD service fires on the order-sign hook — before the order is submitted, the EHR calls our endpoint and we return a card if prior auth is required.”

In documentation: “The CDS service must respond within 5 seconds or the EHR may ignore the response and proceed without displaying cards.”

Relationship to Other Terms

  • CDS — the broader discipline that CDS Hooks implements as a vendor-neutral EHR integration protocol
  • FHIR — the data format for prefetch payloads and context resources in CDS Hooks requests
  • HL7 — the standards body that maintains the CDS Hooks specification
  • Implementation Guide — Da Vinci CRD uses CDS Hooks as its integration mechanism

Common Misconceptions

Misconception: CDS Hooks Is Part of the FHIR Specification

  • Incorrect belief: CDS Hooks is defined within HL7 FHIR as one of its interaction patterns.
  • Reality: CDS Hooks is a separate HL7 standard with its own specification and versioning. It uses FHIR resources in its payloads, but the hook/card protocol itself is independent of the FHIR specification.
  • Why it matters: Implementing a FHIR server does not automatically make a system CDS Hooks compliant — the hook invocation and card response protocol must be explicitly implemented.

Misconception: CDS Hooks Is Only for Drug Alerts

  • Incorrect belief: CDS Hooks is primarily a pharmacy tool for surfacing medication interaction warnings.
  • Reality: CDS Hooks is a general-purpose EHR integration protocol. It is used for prior authorization discovery (Da Vinci CRD), care gap alerts, diagnostic support, referral guidance, and any other scenario where an external service needs to inject guidance into an EHR workflow.
  • Why it matters: Limiting mental models of CDS Hooks to drug alerts causes teams to miss opportunities for broader clinical workflow integration.

Why CDS Hooks Matters

Before CDS Hooks, integrating external clinical logic into an EHR required proprietary integration work for every vendor. CDS Hooks provides a single protocol that any conformant EHR can support, allowing the same CDS service to run across multiple EHR platforms. This is what makes the Da Vinci prior authorization vision technically feasible — a payer’s CRD service can surface requirements in any EHR that supports the order-sign hook.

Cross-References

  • CDS — the broader concept that CDS Hooks implements as a vendor-neutral protocol
  • FHIR — the data format used in CDS Hooks prefetch and context payloads
  • HL7 — the standards body that maintains the CDS Hooks specification

Last reviewed: December 19, 2025 Definition authority: HL7 International Content status: Canonical reference