[Gnumed-devel] test results and therapeutic ranges (was Possible development opportunity)

[J Busser]

Before considering the target range for Patient X with an INR of 
2.0-3.0, can we also consider the handling of a drug whose levels can 
be measured, and which has a therapeutic range which
- may depend on the indication and/or
- may be changed by the doctor who wants it narrower/higher/lower than "usual"

1) have we a suitable place to keep this patient-specific 
information, perhaps linkable to the test, so that when the test 
result is reviewed we can easily discern if we are satisfied?
2) table test_results has fields
- val_normal_min
- val_normal_max
- text field val_normal_range

all of the above are meant to hold values provided by the lab

when a lab supplies for example phenytoin/dilantin result of 56 and 
provides a numeric or text range of 40-80 do we place that in the 
_normal_ field(s) in which case they are no longer _normal_ but 
_reference_  ?

maybe it is better to have a separate set of fields in addition to 
_normal_ considering that when a biologic test like INR comes back at 
1.5, this is abnormally elevated in some people, but it is 
subtherapeutic in someone on warfarin

we could therefore add a set of fields prefixed value_therapeutic etc 
(or value_rx etc)

could it be a good idea to write a patient's corresponding target 
values into the test-result row, either overwriting the lab's 
reference range or (if these must be preserved as original 
communication) into value_target_min and value_target_max?

I am wondering if this would make querying and reporting faster, 
separating patients who will need a change of dosage (needing quicker 
contact) from the others?  Also, once having written the target info 
into the test_result row, the row would remain meaningful even after 
a doctor later raises or lowers Patient X's range. I realize that a 
within-patient history of changes to target ranges should be 
accessible via the audits, but would rather avoid people misjudging 
from the INRs that have been running 2.0 - 2.8 that a patient's 
target is 2.0 - 3.0 when it is in fact 2.5-3.5, not to mention the 
complexity of later trying to assess the quality of anticoagulation 
in one's clinic/practice/surgery.