Closing the loop: How PAS powers real-time prior authorization

Even when coverage rules are clear (via CRD) and documentation is complete (via DTR), prior authorization can still get stuck at the final step: submission, tracking, and response. Providers upload forms through portals, call for updates, or wait days for feedback, while payers manage manual review queues and incomplete requests. 

That’s where Prior Authorization Support (PAS) comes in. Developed under the HL7 Da Vinci project, PAS automates the exchange of prior authorization requests, decisions, and status updates between payers and providers, replacing faxes, phone calls, and portals with standardized FHIR APIs and X12 transactions. 

As the final piece of the electronic prior authorization (ePA) loop, PAS creates a seamless, end-to-end process that moves from request to response in real time. This helps U.S. payers meet CMS-mandated timeframes of 72 hours for expedited requests and 7 days for standard ones, while reducing the administrative burden on both sides. 

How PAS works

PAS connects provider systems and payer endpoints through a standardized workflow that replaces manual review with structured data exchange.

It defines how payers and providers exchange prior authorization requests, responses, and updates electronically using FHIR APIs, while also maintaining interoperability with HIPAA’s X12 278 and 275 transactions for administrative compatibility.

1. Submission

When a provider completes a prior authorization in DTR, the system automatically compiles the request (including patient data, coverage details, and supporting documentation) into a FHIR Bundle. That bundle is sent to the payer’s PAS endpoint (or through an intermediary that can translate to X12 if needed).

2. Response

The payer immediately returns a confirmation that the request was received, and may issue one of the following: 

• A final decision of approval (with authorization number and effective dates) or denial (with a clear, specific reason for denial)
• A pended response requesting additional information and detailing what’s missing to complete the decision.
• A status update if review is ongoing.

3. Follow-up and tracking

If a request is pended, the provider can submit additional documentation through the same API. PAS also supports status checks or subscriptions for automatic updates — no portals or phone calls required.

Example: 
A physician orders a cardiac stress test. The EHR triggers PAS, sending a complete request bundle to the payer. The payer replies “pended”, pending recent lab results. The provider uploads the labs via PAS, and within hours receives an approval — all without leaving their workflow.  

What payers need to implement

For PAS to function effectively, payers must configure their systems to receive, validate, and respond to prior authorization requests through standardized FHIR APIs and X12 workflows. That requires both operational and technical readiness.

Operational requirements

• Decision logic: Define clear, machine-readable rules for approval, denial, or requests for additional information.
• Workflow alignment: Ensure internal utilization management systems connect directly with the PAS endpoint to support timely, automated decisions.
• Response structure: Return standardized elements such as decision status, timestamps, denial reasons, and next steps.

Technical requirements 

• FHIR integration: Implement Da Vinci PAS APIs to receive and return requests electronically.
• Interoperability: Accept and respond to FHIR Bundles, with optional conversion to and from X12 278 transactions for backward compatibility.
• Status management: Support status inquiry and supplemental submission operations to maintain continuity between requests.
• Security and access: Use SMART on FHIR and OAuth 2.0 for secure authentication and data exchange.
• Auditability: Maintain logs and reporting dashboards to track compliance, decision times, and volume trends. 

Together, these capabilities allow payers to automate prior authorization end to end — achieving faster turnaround times, fewer manual interventions, and readiness for CMS-0057-F deadlines. 

Enabling PAS from the provider side   

For providers, PAS delivers visibility and simplicity. Once an authorization request is submitted, the EHR automatically tracks status updates and displays them directly within the workflow. 

To enable this, provider systems (or their vendors) should ensure the system can: 

• Launch PAS directly from the EHR when an order is completed, without leaving the workflow.
• Automatically build the request bundle using existing patient, coverage, and clinical data.
• Attach supplemental documentation (e.g., test results or notes) when requested by the payer.
• Display real-time status updates and decision notifications within the EHR.
• Enable cancellation or modification of requests when care plans change.
• Keep authorizations linked to the original order, so it’s easy to track and follow up later. 

The result: clinicians and administrators get real-time insight into each request’s progress without leaving their system or chasing updates manually. The smoother the integration, the higher the adoption. 

Suggested PAS metrics 

The PAS Implementation Guide includes a set of suggested metrics to help payers and providers assess adoption and efficiency. These aren’t required today, but they’re valuable for performance benchmarking and compliance readiness. 

A few of the key metrics include: 

• Total submissions: Total number of prior authorization requests submitted electronically.
• Total pends & average time to solve: Total number of requests pended due to missing documentation or clarification, and the average time it took to resolve each one.
• Average decision time: Time from submission to final PA result.
• End-to-end success rate: Percentage of requests that result in a final decision (approved or denied) on the first submission.
• Error rate: Percentage of PAS submissions returning an error. 

Tracking these helps identify friction points, optimize turnaround times, and demonstrate ROI for electronic prior authorization. You can view the full list of recommended metrics here. 

The bottom line

Together with CRD and DTR, PAS completes the ePA loop, turning a historically manual process into a digital, connected system that benefits everyone involved. 

For payers, it means faster approvals, compliance with CMS-0057-F timelines, and less administrative overhead. For providers, it means fewer portals, clearer visibility, and less time spent chasing approvals.  And for patients, it means faster access to care. 

By implementing PAS, payers don’t just meet a regulatory mandate. They cut costs, strengthen provider collaboration, and replace fragmented, manual workflows with real-time, FHIR-based data exchange.  

Looking for more info? Get in touch for a chat with one of our prior auth experts.