FHIR Converter is an open source project that enables conversion of health data from legacy formats to FHIR.

The first version of the FHIR Converter released to open source on Mar 6th, 2020. It used Handlebars template language and Javascript runtime. A new converter engine was released on Nov 13, 2020 that uses Liquid templating language and .Net runtime.

Currently, Microsoft supports two types of converter engines, Handlebars engine and Liquid engine, along with templates and filters. We strongly recommend using the Liquid converter for a better alignment with Azure Healthcare APIs, Azure Health Data Services, FHIR Server for Azure, and Microsoft Logic Apps.

The following table shows the differences between two converter engines:

⚠ Rest of this document is about the Liquid converter. For the Handlebars converter, please refer to the Handlebars branch.

Currently, FHIR Converter supports four types of conversions, HL7v2 to FHIR, C-CDA to FHIR, JSON to FHIR and FHIR STU3 to R4. The converter uses templates that define mappings between these different data formats. The templates are written in Liquid templating language and make use of custom filters.

The converter comes with a few ready-to-use templates. If needed, you can create a new template, or modify existing templates to meet your specific conversion requirements. The provided templates are based off of HL7 v2.8. Other versions may require you to make modifications to these templates on your own.

FHIR Converter with DotLiquid engine transforms the input data into FHIR bundles that are persisted to a FHIR server. The converter is integrated into both Azure Health Data Services and Azure API for FHIR, as well as in the open-source FHIR Server as a [$convert-data] #using-convert-data-in-fhir-server) operation. It is also available as a command line tool.

NOTE: FHIR STU3 to R4 conversion is only available in the open-source FHIR Server as a $convert-data operation. It is also available as a command line tool.

The $convert-data operation is integrated into Azure Health Data Services, Azure API for FHIR and FHIR server to run as part of the service. After enabling $convert-data in your server, you can make API calls in the form of <<your FHIR server URL>>/$convert-data to the server to convert your data into FHIR. In the API call request body, you would include parameters such as inputData, inputDataType, templateCollectionReference, and rootTemplate, to specify the message and the type of message you are converting.

For more information on configuring and using $convert-data operation on your server, please refer to these documentation:

• $convert-data for Azure Health Data Services
• $convert-data for Azure API for FHIR
• $convert-data for FHIR Server

The command line tool is another way of converting data, as well as managing templates. The tool converts a folder containing input messages (HL7v2, C-CDA, JSON or FHIR STU3) into FHIR R4 resources. It accepts the following parameters in the command line:

First, build the executable file, Microsoft.Health.Fhir.Liquid.Converter.Tool.exe, in your local directory. Have the input data, as well as the conversion templates, saved in separate folders.

You can run the built .exe file in your terminal by running the following command line and specifying the directories:

>.\Microsoft.Health.Fhir.Liquid.Converter.Tool.exe convert -d myTemplateDirectory -r myRootTemplate -i myInputDataFolder -o myOutputDataFolder

For example, you can run a command like below to convert all C-CDA sample documents inside the SampleData\Ccda folder using the default CCD template:

>.\Microsoft.Health.Fhir.Liquid.Converter.Tool.exe convert -d {path}\Templates\Ccda -r CCD -i {path}\SampleData\Ccda -o {path to your output folder}

After running the command line, there will be a series of "Processing..." lines being written in the terminal window. When the conversion is complete, you will see "Conversion completed!" message.

For example, if you were doing the C-CDA to FHIR conversion in a folder as in the command above, you will see something like this:

Instead of converting multiples messages and documents inside a folder, you can also convert single files using the parameters in the table above. For example, if you were to convert a C-CDA document into a FHIR resource using the CCD template:

>.\Microsoft.Health.Fhir.Liquid.Converter.Tool.exe convert -n {path}\SampleData\Ccda\CCD.ccda -d {path}\Templates\Ccda -f {path to your output json file} -r CCD

The command line tool supports managing different versions of templates from Azure Container Registry (ACR). You can customize templates and store them in your ACR if default templates are not sufficient for meeting conversion requirements. After ACR authentication, you can pull templates from ACR or push templates to ACR using our command line tool.

Note: Template version is aligned with the version of FHIR Converter.

Example command to push a collection of templates to ACR image from a folder:

>.\Microsoft.Health.Fhir.Liquid.Converter.Tool.exe push testacr.azurecr.io/templatetest:default myInputFolder

Example usage of pulling an image of templates in a folder:

>.\Microsoft.Health.Fhir.Liquid.Converter.Tool.exe pull testacr.azurecr.io/templatetest@sha256:412ea84f1bb1a9d98345efb7b427ba89616ec29ac332d543eff9a2161ca12a58 myOutputFolder

For more details on how to push and pull template collections, please refer to the documentation on Template Management CLI tool.

To see the current version of templates we support, check out the complete list of templates.

There are other versions released by Microsoft that are stored in a public ACR healthplatformregistry.azurecr.io. You can directly pull templates from healthplatformregistry.azurecr.io/hl7v2defaulttemplates:<version> without ACR authentication.

There are three documentations to note for HL7v2 to FHIR conversion. Please make sure to reference these as you use our HL7v2 default templates:

• A complete list and explanation of each of the 57 HL7v2 to FHIR conversion templates: see here
• Important points to note for HL7v2 to FHIR conversion: see here
• Common FHIR Validator errors/warning you might run into, and their explanations: see here

The default templates provided with the Converter computes Resource IDs using the input data fields. In order to preserve the generated Resource IDs, the converter creates PUT requests, instead of POST requests in the generated bundles.

For HL7v2 to FHIR conversion, HL7v2 DotLiquid templates help generate FHIR resource IDs from HL7v2 messages. An ID generation template does three things: 1) extract identifiers from the input segment or field; 2) combine the identifers with resource type and base ID (optional) as hash seed; 3) compute hash as output ID.

For C-CDA to FHIR conversion, C-CDA DotLiquid templates generate FHIR resource IDs in two ways: 1) ID generation template helps generate Patient ID and Practitioner ID; 2) the resource IDs for other resources are generated from the resource object directly.

For JSON to FHIR conversion, there is no standardized JSON input message types unlike HL7v2 messages or C-CDA documents. Therefore, instead of default templates we provide you with some sample JSON DotLiquid templates that you can use as a starting guide for your custom JSON conversion templates. You can decide how to generate the resource IDs according to your own inputs, and use our sample templates as a reference.

For FHIR STU3 to R4 conversion, the Resource ID from STU3 resource is copied over to corresponding R4 resource.

The Converter introduces a concept of "base resource/base ID". Base resources are independent entities, like Patient, Organization, Device, etc, whose IDs are defined as base ID. Base IDs could be used to generate IDs for other resources that relate to them. It helps enrich the input for hash and thus reduce ID collision. For example, a Patient ID is used as part of hash input for an AllergyIntolerance ID, as this resource is closely related with a specific patient.

Below is an example where an AllergyIntolerance ID is generated, using ID/AllergyIntolerance template, AL1 segment and patient ID as its base ID. The syntax is {% evaluate [id] using [template] [variables] -%}.

{% evaluate allergyIntoleranceId using 'ID/AllergyIntolerance' AL1: al1Segment, baseId: patientId -%}

The output of converter depends on the templates as well as the quality and richness of input messages. Therefore, it is important that you review and validate the Converter output before using those in production.

In general, you can use HL7 FHIR validator to validate a FHIR resource. You may be able to fix some of the conversion issues by appropriately changing the templates. For other issues, you may need to have a post-processing step in your pipeline.

In some cases, due to lack of field level data in the incoming messages, the Converter may produce resources without useful information or even without ID. You can use Hl7.Fhir.R4 .NET library to filter such resources in your pipeline. Here is the sample code for such purpose.

using Hl7.Fhir.Model;
using Hl7.Fhir.Serialization;
using System;
using System.Collections.Generic;
using System.Linq;

public class PostProcessor
{
    private readonly FhirJsonParser _parser = new FhirJsonParser();

    public IEnumerable<Resource> FilterResources(IEnumerable<string> fhirResources)
    {
        return fhirResources
            .Select(fhirResource => _parser.Parse<Resource>(fhirResource))
            .Where(resource => !IsEmptyResource(resource))
            .Where(resource => !IsIdAbsentResource(resource));
    }

    public bool IsEmptyResource(Resource resource)
    {
        try
        {
            var fhirResource = resource.ToJObject();
            var properties = fhirResource.Properties().Select(property => property.Name);
            // an empty resource contains no properties other than "resourceType" and "id"
            return !properties
                .Where(property => !property.Equals("resourceType"))
                .Where(property => !property.Equals("id"))
                .Any();
        }
        catch (Exception e)
        {
            Console.Error.WriteLine(e.Message);
            // deal with the exception...
        }

        return false;
    }

    public bool IsIdAbsentResource(Resource resource)
    {
        try
        {
            return string.IsNullOrWhiteSpace(resource.Id);
        }
        catch (Exception e)
        {
            Console.Error.WriteLine(e.Message);
            // deal with the exception...
        }
        return false;
    }
}

• Filters summary
• Snippet concept

• DotLiquid wiki
• HL7 Community 2-To-FHIR-Project

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit the CLA site.

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This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.