Re: [Gnumed-devel] lab_request.results_reported_when is not enough to catch re-reported copies of the same result

[Karsten Hilbert]

> This timestamp describes when a *set* of results gets reported  
> however a request can have multiple tests within it, some of which  
> are reported earlier (as partial) and some of which get reported only  
> later, in a transmission that can (and in BC CA does) re-include the  
> already-downloaded partial results.
> 
> Each specific result (observation) has a datetime stamp of when it  
> was made available by the lab.
> 
> The ability to distinguish possibly 3 or 4 copies of the same result  
> will be helped if we would keep, in test_result, in a column what  
> would be
> 
>       test_result.result_reported_when (which does not yet exist)
> 
> which can be supplied by
> 
>       OBX 014 Date-Time of Observation (Test resulted by laboratory  
> timestamp)

Well, test_result, courtesy of being a child of clin.clin_root_item
has a field clin_when which might hold that information.

Now, there's a conceptual difficulty in this:

When really is when ? Does "clinical time" mean "when the sample was
taken" or does it mean "when the value was derived at the lab". The
former assumes changing of the value stops when, say, the blood leaves
the body and enters the probe tube while the latter assumes that the
value keeps on changing - both of which are correct.

Ureic acid doesn't change.
Kalium certainly does.

So, some rate of change is to be expected even if small. If no change
happens all the better :-)  Hence assuming clin_when to be the time
when the value was measured (to the best we know - this might be the
time the lab provided the value to us) is likely safest.

OpenEHR defines three times regarding health care:

- time of clinical truth
- time of result obtained
- time of data entered into the EMR

Many times 1 and 2 will coincide but not always. GNUmed distinguishes
1+2 from 3: clin_when vs. modified_when.

Karsten
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