Monday, January 14, 2013

What is a Hospitalization?

An interesting issue on the HQMF ballot came up today in the HL7 Structured Documents workgroup that I thought was worth talking about here.  The concept that was needed was "hospitalization".  But what is that?

The short answer is it's rather complicated.  The (really) long answer is below:

Let me first describe a situation:

A patient suffers stomach pain, goes to the emergency room, is evaluated and treated, and transferred to a bed for observation.  After about 20 hours, they have not gotten better, and so are admitted to the hospital.  They undergo a series of diagnostic tests, and after the doctors figure out what is wrong with them and diagnoses them, they are transferred to another facility for treatment. After treatment, they are then transferred back to the original facility.  They are then discharged home.  They have a follow up visit with a specialist, who recommends therapy.  The patient walks over to therapy, and starts the first course the same day.  After the last therapy visit the patient has another follow-up with the specialist (again on the same day).  And then there is a final phone conversation with their general provider before they are finished with the condition.

In the HL7 RIM, these various events are modeled as a PatientEncounter.  The definition of encounter in the RIM is: An interaction between a patient and care provider(s) for the purpose of providing healthcare-related service(s).

Examples given in the RIM include: Outpatient visit to multiple departments, home health support (including physical therapy), inpatient hospital stay, emergency room visit, field visit (e.g., traffic accident), office visit, occupational therapy, telephone call.

So let us attempt to identify all of the "encounters" this patient had.  We'll get to hospitalization eventually, but we need these concepts first.
  1. The emergency room visit.
  2. The admission for observation.
  3. The subsequent admission to the hospital.
  4. The transfer to another facility.
  5. The transfer back to the original hospital.
  6. The first follow-up with the specialist.
  7. Six visits to therapy
  8. The second follow-up with the specialist.
  9. The phone conversation with the GP.
Except that in some cases, #1 and #2 could be part of the same encounter by some views, or it might be that #2 and #3 are parts of the same encounter, or #1, #2 and #3 could be considered to be a single hospitalization.  #3, #4 and #5 are each separate except for the case where the other facility and the original hospital are treated as the same entity, in which case they could be treated as one encounter.  Encounter #6, and the first encounter of #7 could be considered to be part of the same encounter, as could the last visit of #7 and visit #8 (under the single visit to multiple departments, if PT and the specialist are simply different departments of the same organization).  The therapist might even describe all of #7 as one encounter.  It's pretty clear the hospitalization stops after encounter #5, but where does it start?  Don't worry, I'll get there.

Patient Views of an Episode
Consider another case, treatment for arthritis of the knee.  Imaging the treatment includes two different attempts at physical therapy, an MRI, an injection, and finally surgery followed up by more PT.

Imagine I want to look at how much treatment for arthritis costs.  There are a lot of ways I could view this.  How much did the surgery cost me could cover both surgery and PT, or just surgery depending on what I mean.  Did I mean just the surgery, or the surgery and the necessary followup care.  On the MRI, did I just mean the MRI, or also the pre- and post-MRI visits to the specialist to review the condition, order the MRI, and evaluate the results.  How much did PT cost could mean each session separately, or all of them together.
Now we introduce another concept, which is a super-set of hospitalization, called the episode of care.  Episode of care is not defined in the RIM, nor can I find an adequate description of it.  What constitutes an episode of care varies depending on context.  From the patient perspective, the broadest view of the episode of care goes from onset to resolution of the condition.  But it also might vary depending on what they want to discover (see the sidebar).  The specialist might consider this episode to be from step 6 to step 8.  The original hospital might go from 1 - 5, or perhaps 2-5.  The therapists view would include all six therapy visits.

Now, imagine that you have a quality measure that is intended to address the cases I described above.  How would you describe the episode of care, and/or the encounters related to the episode of care.

This isn't a failing of the HL7 RIM.  In this case, it is a failure to include adequate definitions of the term encounter and episode in defining the quality measure.  It is further complicated by the fact that there are varying administrative definitions for encounter and/or episode depending on who you might be dealing with (e.g., CMS), and there may also be clinical definitions for some well-defined episodes of care (e.g., pregnancy).

Administrative definitions of encounter don't seem to be that helpful in quality measures, because they depend on organization structures that may vary.  So, even though clinically the sequence of events might be identical for a given patient, they could be treated differently if you looked at administrative definitions.

We could be rigorous in our definitions, but that won't solve the problem.  Let me illustrate.

Suppose we were to define an encounter as a single contiguous stay, within one care setting (ED, Ambulatory, or Outpatient), at the same location.  We'd have to be more specific about definition of "same location".  My first refinement of that was "same physical location", but then I had to think about medical centers and some hospitals I know.  My next refinement came up with the same building, or complex of buildings, on a contiguous property, being operated by the same organization.  I had to refine the latter, to be the fuzzier "giving the outward appearance of being operated by the same organization" because some complexes are, and some aren't operated by the same organization.  And I'd further have to relax contiguous property to address outliers, like the office one or two blocks over that was leased to address space overflow issues.   Then I'd have to get more concrete because these definitions are way too fuzzy.  For the purpose of argument, assume I have.

And then assume I'm satisfied with this.  So, here it comes: I could define a hospitalization as an episode of care defined as a sequence of contiguous encounters at the same location (as not really described above) where at least one of the encounters is an inpatient setting.  Finally, phew!

It seems as if I've adequately defined my way around the ambiguity, and we could write the measure.  Let's say that I'm satisfied with these definitions (which is a big leap), and that you are satisfied with them as well (an even bigger leap).

While you could now define a quality measure about a hospitalization, the definitions that I've given does not operate on the data that most systems capture.  Encounter is principally an administrative concept, and the data about it is captured using administrative definitions, not rigorous definitions  imposed by some misguided, though perhaps well-meaning standards geek. Even though what I've defined allows me to distinguish encounter's 3, 4 and 5, they may be simply captured as one encounter at some organizations, and they may not have the necessary data to distinguish those as separate encounters.

So, are we back to the drawing board?  Perhaps, and perhaps not.  I think the idea of coming up with operational1 (rather than administrative) definitions of encounter, episode of care, and concepts like hospitalization, will be useful going forward.  Organizations will have to map from what they capture (mostly administrative) to the operational definitions.  The value of having consistent operational definitions of these concepts is that it makes quality measures more comparable, and less sensitive to administrative variations.

But it won't happen overnight, and it will take some time for these operational definitions to come into use in Health IT solutions.

-- Keith

1 I call these operational, because they are being used in quality measures, which is the operations part of TPO (treatment, payment and operations).  There are also clinical definitions for episodes of care (e.g, pregnancy can be pretty well defined clinically).  There may be different clinical definitions for encounter, but I think that's probably too many angels dancing at this point.


  1. Hi Keith,

    In the RIM, "Episode of Care" would be a CareProvision in Event mood with a subject of a particular problem.

  2. Hi Keith,

    Welcome to the wonderful world of encounters. The PA and PC HL7 groups have had tons of discussions about this issue, and especially if you throw international requirements into the mix it gets complicated rather quickly. See HL7 Wiki for an attempt at describing the various layers of encounters or encounter groupers.


  3. Nice post. What about the case where a patient gets up and walks out of the hospital to the 7-11 across the street to buy a pack of smokes? By your definition, that makes it two hospitalizations I think. Brief interruptions in hospitalizations do happen. It is not unknown for a physician to give a patient a "pass" out of the hospital for brief periods either, when warranted.