Re: [Gnumed-devel] basic test types

[Karsten Hilbert]

> Let us say we prefer mmol/dL, and test_org 6 reports in mmol/L, but 
> test_orgs 7 and 8 report in mg/dL:
> 
> TEST_RESULT (recalling that this table does not directly identify the 
> lab, only its tests)
> 
> >  FK_TYPE / VAL_NUM / VAL_UNIT
> >    1     /   6.1   /   mmol/L
> >    2     /   108   /   mg/dL
> >    3     /   123   /   mg/dL
> 
> Let us say that, based on the original importer values, we have in 
> test_type:
> 
> TEST_TYPE:
> 
> > FK_TEST_ORG/ CONVERSION_UNIT /   CODE  / CODING_SYSTEM / NAME
> >    6       /       mmol/L    / 14769-4 / LOINC         / GLUCOSE, FASTING
> >    7       /       mg/dL     / 14769-4 / LOINC         / GLUCOSE, FASTING
> >    8       /       mg/dL     / 14769-4 / LOINC         / GLUCOSE, FASTING
> 
> So here a user would decide "for fk_test_org (lab) 7, code 14769-4, 
> LOINC" I want that expressed in mmol/L.
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
No, I think the purpose of that field still isn't clear. It is
of no concern what unit the lab actually reports results in.
It also is of no concern which unit I want to eventually see.
What the row

> > FK_TEST_ORG/ CONVERSION_UNIT /   CODE  / CODING_SYSTEM / NAME
> >    6       /       mmol/L    / 14769-4 / LOINC         / GLUCOSE, FASTING

basically says is this:
"lab 6" reports "glucose, fasting" with code "14769-4" from
"LOINC" - and should you want to compute anything with the
results for this test you first need to convert them to
"mmol/L".

IOW: for each and every row in test_type that represents the
same clinical test (eg. various types of blood glucose) the
conversion_unit should be the *same* !

Or yet again in other words: Should one want to compute
anything with length measurements - no matter whether they
came in feet, yards, centimeters or meters - they must be
converted to millimeters first. So "mm" would be the
conversion_unit.

> But is it not redundant to have mmol/L in all three rows, and to have 
> to repeat this manually when a new lab should make its results 
> available to you but in mg/dL?
Sounds like it, then, yes.

> It could be in a test_conversion table where the standard 
> name could reside - but now I am wondering does this overlap 
> test_type_local and should the conversion be absorbed there?
I wouldn't want to force the use of test_type_local on people.
After all they might choose to not use that unit for a given
test_type or not use a test_type_local name for it. However,
it might make sense to *also* provide a conversion_unit for
test_type_local rows ...

> The only proviso here is whether we can trust that two different labs 
> will never send us two results where each has the same (code, coding 
> system) but in fact the records represent two *different* entities.
That might happen, most often when coding_system is NULL.
Other than that I don't see this happening without it being a
good reason for changing things lab-side.

Karsten
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