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[Gnumed-devel] Fwd: Re: [Egadss-devel] variance in test units with repea

From: J Busser
Subject: [Gnumed-devel] Fwd: Re: [Egadss-devel] variance in test units with repeated measures (was A1C Lab Test Value)
Date: Mon, 23 Jan 2006 21:38:59 -0800

Forwarded for interest, from the egadss-devel list, on how tests that can be reported in a variety of units might be handled by clinical guideline software.

From: Glen McCallum <address@hidden>
Subject: Re: [Egadss-devel] variance in test units with repeated measures (was A1C Lab Test Value)
To: address@hidden
Date: Mon, 23 Jan 2006 12:40:15 -0800

Hi Jim,

<response in line>
On 22-Jan-06, at 9:47 AM, J Busser wrote:

At 11:49 AM -0800 1/20/06, Glen McCallum wrote:
...COMPETE returned 0.07 as the value of the A1C test whereas we return value=7 and unit=% (hence that what I look for in the Arden Syntax).

Would 0.07 have a unit value of "unity", else "/1", else a null value for units? Not sure if there is a standard expression for this.

Likewise, are any of the characters/expressions "%" or "/100" or or "100^-1" considered "standard"?

I'll defer this one Iryna. She's more familiar with CDA templates and the interface with the EMR.

I know that within a single EMR, is it possible for a single patient to have a series of values that have been expressed in different units. AFAIK, few EMRs provide the means to process (e.g. translate / express in a equivalent form) such a series. So it's interesting to consider how such a dilemma could be resolved (if it all) via EGADSS. For example, I don't know whether a change in units in which a test is reported will result in a change in its LOINC code.
Definitely interesting. We're getting more and more into LOINC as we work with lab test data.

I suppose the use cases for EGADSS would include:

- different EMRs each accessing EGADDS with the same test of interest but whose units are different

- any one EMR accessing an EGADSS guideline that employs/requires a series of repeated measures on a single test, where within that series, the results had been stored using different units.
I'm certainly interested in how or if our CDA Template restricts these conditions. Iryna?

Is there so far within EGADSS a guideline that must handle a repeated measure?
No. The guidelines that we've been encoding recently always reference the value of the most recent test.

A specific use case --- challenging despite adherence to a single test unit --- would be ongoing blood thinning aka anticoagulation. A "normal" result for this test, for a patient not receiving anticoagulation, is around 1.0. A target on-therapy range is typically 2.0 - 3.0 or 2.5 - 3.5, or could even be locally-defined. There is value to being able to flag a single result as whether it lies inside or outside the desired range, kind of like a single glucose value for a diabetic. But to express treatment results over time, repeated measures on the test result known as the INR should be processed to achieve the % of time that the result is within the target range. Where a consecutive pair of results crosses the target range, one method applies linear interpolation to the time interval between them, to apportion the segments as in- or out-of range. A variant method could determine how often a patient is "close" to range, e.g. for a target range of 2.0 - 3.0 it might determine the percent of time that a patient is between 1.7 and 3.5.
This would be a nice application for fuzzy logic.

I suspect the time-based interpolation is important. Is it already part of the design or the plan, or something to consider, perhaps for EGADSS v2 or 3?


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