Query a Da Vinci PDex Formulary server for drug coverage using InsurancePlan and MedicationKnowledge resources

In-depth guide

Steps

1. Discover available formularies: GET /InsurancePlan?type=drug to retrieve InsurancePlan resources profiled as Formulary (usdf-PayerInsurancePlan); each InsurancePlan represents a drug formulary and includes coverage area and plan period
2. Retrieve FormularyItem resources linked to a specific formulary: GET /Basic?code=formulary-item&formulary=<InsurancePlan-id> — FormularyItem (profiled Basic resource) captures the drug's relationship to the formulary including drug tier, prior authorization flag, step therapy, and quantity limits
3. Retrieve the FormularyDrug (MedicationKnowledge): GET /MedicationKnowledge?_id=<id> or GET /MedicationKnowledge?drug-name=<name> — FormularyDrug holds the RxNorm drug code, dose form, and is linked from FormularyItem.subject
4. To find coverage for a specific drug: search MedicationKnowledge by RxNorm code (GET /MedicationKnowledge?code=<RxNorm-code>), then retrieve linked FormularyItem resources to determine tier, cost-sharing, and restrictions per plan
5. Inspect FormularyItem extensions for drug-tier-id (referencing the cost-sharing tier defined in InsurancePlan.plan.specificCost), prior-auth (boolean), and step-therapy-limit to assess what the plan requires before covering the drug
6. Validate search responses against the usdf-PayerInsurancePlan, usdf-FormularyItem, and usdf-FormularyDrug profiles from the hl7.fhir.us.davinci-drug-formulary#2.1.0 package