The primary objective of this study was to measure the extent to which the FHIR® standard accurately represented the data elements required to support data acquisition for and submission to three nationally recognized registries. The study team selected three registries to which the University of Arkansas for Medical Sciences regularly supplies data ‒ the Trauma, Stroke, and National Surgical Quality Improvement Program (NSQIP) registries (Table 1). We consulted the full list of registries located on the Arkansas Department of Health website and identified the most popular registries with the broadest, national presence for generalizability. Data dictionaries3 for each registry were publicly available and used for mapping to the FHIR® standard.
Table 1
Registry | Population | Clinical Focus | State Registry | National Registry |
Trauma | Adult / Pediatric | Trauma, Injury | Arkansas Trauma Registry | National Trauma Data Bank (NTDB®) |
Stroke | Adult | Acute Stroke Care | Arkansas Stroke Registry | National Acute Stroke Program |
NSQIP | Adult / Pediatric | Surgery, Surgical Complications | ‒ | National Surgical Quality Improvement Program (NSQIP) |
Registry: name of the registry of interest; Population: population supported by the registry (adult vs. pediatric vs. both); Clinical Focus: clinical focus or domain area of interest of the registry; State Registry: name of the state-based registry program associated with the registry of interest; National Registry: name of the nationally recognized registry program.
A systematic mapping approach, developed by Garza and colleagues [19], was used to conduct the Registry-to-FHIR data element mappings. Registry data elements were mapped using the latest version (at the time this work was started) of the base standard ‒ the HL7® FHIR® Version Release 4b (FHIR® R4b) standard [10] ‒ the FHIR® US Core Profiles, Release 4 (US Core R4), and the US Core Implementation Guide STU4 [20].
Two independent team members conducted the mappings between the registry case report forms (CRFs) and the FHIR® standard, hereinafter referred to as the Registry-to-FHIR mappings. Mappers first identified the appropriate FHIR® resource for a registry data element, and then identified the appropriate data element(s) within the resource that best fit the registry data element based on its definition. Permissible values and data type were considered in situations where those were not extensible in the FHIR® resource. In other words, data elements that were flexible enough, were mapped to FHIR® resources even if the example resource coding did not match the registry values perfectly. Briefly, for coded data elements, those with permissible value lists (e.g., controlled terminologies, code sets, or value sets) FHIR® offers different binding strengths that are “associated with various degrees of flexibility as to how closely the value set should be followed”: Required, Extensible, Preferred, Example [21].
In situations where our data element captured more values than those in a resource using a Required binding, we would need to determine if we would be able to fit our code list by mapping values to the ‘other’ option ‒ accepting the information loss ‒ or else consider this as “Not Available in FHIR” for our use case. However, in situations where the resource used Extensible bindings, if the concepts in the registry permissible value set do not match at all, alternate codes can be used instead, and we could consider this as “Available in FHIR” so long as the data element definition matches the definition in our use case. Even more flexibility is available for data elements with Preferred and Example bindings, which are completely optional. For example, Procedure.code uses ‘SNOMED CT’ as an example binding, which gives us the option to use SNOMED CT, but does not limit us to that code set. Instead, we could use CPT codes and consider this data element as “Available in FHIR” so long as the definition matches that of our use case.
Adjudications of the Registry-to-FHIR mappings were performed by three members of the research team (2 mappers, 1 principal investigator) to achieve consensus prior to the analysis to address any conflicts in the mappings. The principal investigator performed a cursory review of the two mappings, consolidated the mappings into a singular dataset, and identified those that were not in agreement. The adjudication team then discussed the conflicting data elements and determined the final mapping for each through a consensus-driven approach. In the event consensus could not be reached, the principal investigator made the final decision after seeking input from the HL7® community.
As a result of the Registry-to-FHIR mappings, data elements for each registry were categorized into two groups: “Available in FHIR” and “Not Available in FHIR”. These categories were used to calculate the actual coverage of the standard and a percentage for each category. Following the same criteria for coverage as prior mapping work by Garza and colleagues [22], we considered a data element as Available in FHIR “…if (1) it has a corresponding data element available within one of the FHIR® resources or (2) if the data can be captured or derived using a combination of data elements across one or more resources.” This represented the transformation between FHIR® resources and the corresponding registry. The FHIR® coverage measure was calculated as a percentage (total data elements Available in FHIR vs. total data elements overall).
In addition, in an effort to identify the clinical domain areas with the least and most coverage, we analyzed coverage across the different domain areas for each registry. We further analyzed the complexities of the mappings by reviewing the total number of resources needed to fully capture the context specific to a particular registry data element. For example, ‘Date of Birth’ would be considered a one-to-one mapping (least complex), as the singular registry data element would map directly to the ‘birthDate’ data element within the Patient Resource. However, ‘CT Date/Time’ would be slightly more complex, as it would require mapping to the Procedure Resource to capture the date/time component, but also require mapping to (or reference to) the Encounter Resource to ensure that the Procedure occurred during the specified encounter. In this case, at least three FHIR® data elements would be required: Procedure.code (to specify the type of procedure as a ‘CT’), Procedure.occurrence[x] (to capture the date/time component), and Procedure.encounter (to reference back to the Encounter Resource and ensure this procedure occurred during our encounter of interest).
[3] Data Dictionaries:
(1) Trauma ‒ (a) https://www.healthy.arkansas.gov/images/uploads/pdf/ATR_2023_Data_Dictionary_-_part_1.pdf, (b) https://www.healthy.arkansas.gov/programs-services/topics/arkansas-trauma-registry-atr; (2) Stroke ‒ (a) https://www.heart.org/-/media/Files/Professional/Quality-Improvement/Get-With-the-Guidelines/Get-With-The-Guidelines-Stroke/Stroke--Diabetes-CRFJuly21.pdf, (b) https://www.heart.org/-/media/Files/Professional/Quality-Improvement/Get-With-the-Guidelines/Get-With-The-Guidelines-Stroke/Stroke-30Day-FollowUp-Form-CRF.pdf; (3) NSQIP ‒ https://www.facs.org/media/yaol5yoj/nsqip_puf_userguide_2020.pdf