Setting thresholds

Thomas Beale thomas.beale at
Wed Feb 28 08:17:57 EST 2018

Although Jussara is right in terms of reference ranges generally, i.e. 
what you see in a pathology handbook as ref ranges for male / female / 
child for say Total Cholesterol or some other analyte, the openEHR 
Reference Model does allow reference ranges to be carried in DV_QUANTITY 
(see here on the UML site 
DV_ORDERED.normal_range and other_reference_ranges). We do this for the 
same reasons Karsten explicates below.

The idea is that the normal range (and other ranges) /specific to the 
patient type for the current test order/ (sex, age, sometimes 'race', 
e.g. African American cholesterol normal range is +10%) can be written 
into the data. So, say the patient is a 64 yo female caucasian, and the 
analyte is 'total cholesterol'. The ref range will be (something like):

  * normal range: 159-276 mg/dL or in SI, 4.12-7.15 mmol/L

that is just one row from a table of normal ranges keyed by sex, age and 
with the modifier for African Americans (I have a US path manual, 
probably it is just 'African' elsewhere).

The reference range data is often influenced by other factors depending 
on what it is, e.g. location, diet, and so on.

The point is, that the path lab can help the doc by including the 
relevant normal range with the measured value, and therefore also 
generate an 'abnormal' indicator in the result. This is a significant 
time-saver for doctors, and it also has the effect of writing into the 
EHR the reference range that was actually used to decide that the 
patient was abnormal for that analyte and to intervene - i.e. it's the 
reference knowledge for the assessment.

- thomas

On 28/02/2018 12:43, Karsten Hilbert wrote:
> On Wed, Feb 28, 2018 at 12:18:24PM +0000, Jussara Macedo Rötzsch wrote:
>> Ranges  aren’t actually part   of the Information model, they are rules for
>> decision support, and therefore belong to the Application level, like a gdl
>> based CDS
> In practice there are still needs to store ranges (with the data):
> 1) path labs will attach ranges to recommended interpretations
> 	those are best stored "with" the result(-interpretation)
> 	and, no, it is not sufficient to attach them to the test
> 	*type* of a measurement
> 2) ranges applied by a clinician upon which a conclusion
>     has been made
> 	those will often end up as textual part of a SOAP note
> Think of a patient with warfarin monitoring: The lab will cry
> foul (if not properly informed) but the clinician is happy
> when the INR is in the therapeutic range.
> GNUmed "solves" that by allowing to attach both a "nominal"
> and a "desired" range to each test result.
> For what that's worth.
> Karsten

Thomas Beale
Principal, Ars Semantica <>
Consultant, ABD Team, Intermountain Healthcare 
Management Board, Specifications Program Lead, openEHR Foundation 
Chartered IT Professional Fellow, BCS, British Computer Society 
Health IT blog <> | Culture blog 
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