Converting UCUM Units with FHIR

06.09.2022

Ensuring interoperability between various healthcare IT systems requires multiple standards. Among them is FHIR, developed by the HL7 standards organization, which is the newest and most promising one. Its adoption has been growing recently. Such standards play a key role in organizing data into comprehensive structures as it moves between systems. 

Each health organization, whether a hospital or laboratory, tends to use its own numerical unit representation, depending on various factors. As a result, this discrepancy in data can pose significant challenges to interoperability. 

For example, when creating a common database in the FDA’s Mini Sentinel project and then combining the data, researchers have found 68 different platelet count result units in the data. 

The standardization of numerical data might not seem like a big problem, but it is, especially for interoperability. For this reason, HL7 recommends using UCUM (Unified Code for Units of Measure) when adopting FHIR.

What is UCUM?

To understand the role of UCUM in unit standardization, let’s first examine what it is. UCUM was originally developed by Gunther Schadow and Clem McDonald and is now distributed and made available by the Regenstrief Institute, Inc. 

UCUM is a code system that aims to include all modern units of measure used in science, engineering, and business. Its main goal is to provide a clear means of communication between different systems. UCUM works with metric as well as empirical units such as feet and inches.

While typically used for electronic data interchange (EDI) protocols, it can also be applied in other types of machine communication. The code system has been adopted by several large standards organizations, including IEEE, DICOM, HL7, and ISO’s 11240:2012 specification about medicinal product characteristics. 

How the UCUM conversion works

The Unified Code for Units of Measure assigns to each defined unit a specific meaning based on dimensional analysis, as it’s not enough for different systems to just use the same symbols to facilitate interoperability. UCUM has a formal syntax that can be validated and a matrix of coefficients that define the values expressed by various commensurate units.

UCUM provides a single coding system for units; as such, it’s easy to see how it can help establish interoperability. 

There are many tools available that help perform a conversion and validation of quantities with UCUM units. However, it’s possible to forgo that step with an FHIR server that provides a built-in UCUM unit conversation. 

Unit conversion in the Kodjin FHIR server

Our team has implemented full support for the UCUM expression syntax in our Kodjin FHIR server. It is part of the Kodjin FHIR suite and has two main functions:

  • String validation

The server checks to see if the entered string matches the unit code in the UCUM codes table. If not found, the string is tested for typical syntax errors such as missing brackets. The error and its reason are then reported in a message box.

  • Filtering by value 

This function converts numerical values and filters data in base units. When no exact match for a unit name is found, the server searches for all possible units with a single search term corresponding to the unit’s synonyms or name. 

Such filtering can be done in meters, even if the source data is in feet or centimeters. The system understands that 170 centimeters are equal to 1.7 meters, for example.

Having the UCUM conversion capabilities built into your FHIR server saves you time and improves data quality, as you won’t have to manually load, validate, and convert all the unit’s data with third-party tools.

Contact us to learn more and get a demo of our Kodjin FHIR server that supports UCUM conversion.

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