Submit a prior authorization request using Da Vinci PAS (Prior Authorization Support) FHIR operations and handle pend/approve/deny responses

Steps

1. Construct a PAS Bundle: a ClaimResponse-referenced Claim resource (type = 'preauthorization') containing patient, insurer, provider, and item details with X12 278-equivalent data mapped to FHIR elements using the PAS profiles
2. POST the Bundle to the payer's or intermediary's '$submit' operation endpoint; include the Authorization header with YOUR_TOKEN obtained via SMART backend services or OAuth2 client credentials
3. Inspect the synchronous ClaimResponse: outcome 'complete' with adjudication.category = 'submitted' and item.adjudication indicating approved/denied/pended; extract the preAuthRef string for approved items
4. If outcome is 'queued' (pended), the payer will send an unsolicited response later; implement a FHIR Subscription or polling loop on the ClaimResponse resource using the id returned in the response location header
5. For a denied response parse the ClaimResponse.error and ClaimResponse.item.adjudication.reason CodeableConcepts; map reason codes to CARC/RARC equivalents for display and appeal workflow
6. Attach the ClaimResponse.preAuthRef values to the downstream 837 claim in REF*G1 segments to avoid claim denial for missing authorization