The conference center was,
virtually speaking, on fire (spelled FHIR in HL7 terminology) as FHIR was the
hot topic of the meeting Jan. 19-24. FHIR stands for Fast Health Interoperable
Resources, which is basically using web technology to exchange medical
information. It is touted as the new interface standard that will eventually
replace the versions 2 and 3. But before describing what this is all about,
let’s take a step back and find out how HL7 got to this new venture.
HL7 has a lot of experience when
it comes to defining new interface standards and there have been good learning
experiences. The first widely implemented iteration, version 2.x has been a
huge success from an implementation perspective as it has pretty much become the
way that the vast majority of the healthcare applications exchange information
in the US and many other countries. The main complaint is that “if you have
seen one interface, you have seen one interface,” meaning that no two
implementations are alike. Also, even though the messaging is kind of ugly and
ancient, people know the weaknesses and use Interface engines extensively to
map the messages to provide interoperability. So, in short, “it kind of works.”
Version 3 was supposed to solve
many of the flaws in version 2, however, except for a few implementations in
Canada and the UK, it has gained very little traction. The main complaint of version
3 has been its complexity and verbosity. Take specification of patient sex as
an example. In version 2 one would specify in the eighth element of the Person
Identifier (PID) Segment, the value of “M” for male. In version 3 this same
element would have to be encoded in XML and basically specify that “of a
particular code system with a specific code name,” the AdminsitrativeGenderCode
would be “F,” with the display name being “Female” etc. In other words, what
takes a single character in version 2 takes at least 3 lines of text in version
3 to describe exactly the same information. Therefore, early implementers would
find out that going from version 2 to version 3 would choke the bandwidth of the system due to
the lengthy message exchanges. This is in addition to the fact that there are
not very many version 3 tools, and it is complex. Furthermore, its information model
(Reference Information Model or RIM) is trying to cover all of the possible
constraints, use cases, and specializations, and that makes it very cumbersome.
In a nutshell, it is great for academics, but a pain for implementers.
There are quite a few
implementations of the Clinical Document Architecture (CDA) in the US, as the Meaningful
Use (MU) requirements for Electronic Health Record (EHR) implementations have made
it a major priority. However, the level of interoperability for these documents
has been a challenge. Yes, the definitions of templates such as the
Consolidated CDA (CCDA) has been a major help, but they are still relatively
verbose and complex to create and parse. As with other v3 components, the
standard does not have very many friends among implementers.
What does Fast Health
Interoperable Resources, FHIR, do that you can’t do by using either version 2,
version 3 or a CDA? First of all, the specification started with a clean slate,
so instead of making an attempt to model the world of healthcare, which is what
the RIM did for version 3, and trying to cover every possible use case, it
started bottom up and defining the entities or what FHIR calls the resources that
are needed to exchange information. The maximum number of these resources is estimated
to be 150, the draft standard for trial use (DSTU) as published recently has
about 50 to start with. Then it put restrictions on these resources by stipulating
that they should cover 80 percent of the common scenarios, no less, but
definitely no more. The remaining 20 percent that is critical to achieve interoperability
is then achieved by profiling and extensions. The requirement is that these
extensions be published, and therefore be accessible to anyone who is trying to
exchange information.
The requirements for FHIR are that
it should be very easy and fast to implement, it leverages web technologies,
messages are human readable, and it supports multiple architectures. There are
several reference implementations and test servers available, all in the public
domain. There is also a big library of examples. Collections are represented
using the ATOM syndication standard. Without going into too much technical
detail, ATOM is how Facebook and Twitter feeds work, and has become a
semi-standard in the web environment.
I initially thought to myself that
FHIR was equivalent to REST (Representational State Transfer), in other words
the equivalent of the recent DICOM extensions for web access to images
(WADO-RS). REST considers everything to be a web resource, which can be
identified by a uniform resource
identifier (URI) or
internet identification. However, FHIR is more than that, there are actually four
different interoperability options, which are called paradigms. Yes it includes
REST, but also a document standard, messaging standard, and a set of services.
REST provides standard operations using http, using the widespread experience
of implementers in this domain. The documents defined in FHIR are similar to
CDA, and consist of a collection of resources. Example resources are a patient,
practitioner, allergy, family history, care plan, etc. Resources can be sent as
an ATOM feed, which allows also for sign-in and authentication. Messaging is
also very similar to v2 and v3. The services are based on a Service Oriented
Architecture (SOA). Remember that regardless of which paradigm is used, the resource,
i.e. content of the information, is still the same, so it can be shared using
different paradigms. Compare this with sending a letter from A to B using FEDEX
and then from B to C using UPS. Similarly, the content might be a lab result
that is received in a message and forwarded in a discharge document. The
profile definitions that are critical for interoperability are also shared
among the different paradigms.
Based on the many advantages, one
might wonder why there are no implementations (yet) of FHIR to speak of. First
of all, it is brand new, and there is obviously a learning curve for
implementers (albeit very small compared with version 3 or CDA implementations).
Second, there is no incentive to replace a huge installed base of v2 and a decent
number of CDA implementations. However, for new domain areas where healthcare
is just starting to get traction, such as mobile implementations, it is a great
tool. In addition, for any social media applications, it would fit in very well
too. To the extent that new applications are being driven by implementers,
there could definitely be a major push towards its adoption.
FHIR has a lot of
potential, not necessarily as a replacement for existing implementations but to
augment new applications, which are based on web technologies. Its many
examples, public domain reference implementations, and test servers are a major
draw. During the recent FHIR connectathon at the HL7 meeting, it became obvious
that it is relatively easy to create a simple implementation very quickly. FHIR
might become the backbone of the next generation healthcare IT implementations,
but then… who knows what might come along in another five years or so. Time
will tell, in the meantime, there is no question that there was a lot of smoke
around FHIR at the HL7 meeting.