FHIRPath Editor

The article describes how to write FhirPath expressions for calculations, enable-when logic and population using the FHIRPath editor

The FHIRPath Expression Editor is a tool designed for non-technical users working with electronic medical forms based on the FHIR Questionnaire resource. It offers a low-code environment for creating, editing, and testing FHIRPath expressions that support dynamic behavior, calculations, data population, and named expressions within forms.

Key Use Cases:

• Enable or disable fields dynamically

• Calculate values (e.g., scores, age, BMI)

• Pre-fill form fields using existing data

• Define and reuse named expressions

How to Use the FHIRPath Editor

1. Create an Expression

After creating the form and adding a set of fields:

• Navigate to the Rules section of the field where you want to apply logic.

• Select one of the expressions: Enable-when, Calculated, or Population.

• Click Visual Mode to open the FHIRPath Expression Editor.

• Set any variables (named expressions) you want to use in the expression.

• Write your final FHIRPath expression using the editor interface.

2. Test and Debug an Expression

After writing your expression:

• Fill out the form as a user would.

• Open the Debug Console to test and debug how your expression behaves with actual data.

• Close the FHIRPath Editor panel when you're finished. Any expressions you've written are saved automatically into the Questionnaire resource.

Validation and Error Handling

• Automatic Validation: FHIRPath expressions are validated in real time.

• Error Highlighting: If there are issues with syntax or logic, errors will be highlighted directly in the editor for easy correction.