Heath Frankel wrote: > Rodrigo, > I am jumping in late in the > The DV_QUANTITY (or technically the DV_ORDERED abstract class) data > type represents the reference range specified by the lab using the the > normal_range relationship. There is also other_reference_ranges to > represent all possible reference range differentiated by various > patient context such as pregnant female, etc. The normal_range is > used for the range that is applicable to this subject. > > The is_normal method in DV_ORDERED allows it to compare the > actual quantified magnitude with the normal range and return an > indicate that it is normal or not. You can use this to raise your > alert of abnormal results when is_normal returns false. > > The XML schema published with openEHR Release 1 actually went one step > further and I believe it is a necessary addition to the reference > model. It treats is_normal as an attribute and allows you to > optionally specify the value of is_normal rather than it being calculated. > This is useful when transforming HL7 Lab data into openEHR and > Pathologists seem to not like downstream manipulation and > interpretation of raw data in case the original data is > mis-interpreted. This has lead to particular best-practice in > Australia where lab data provided in atomic form also needs to have a > full text report included along with the atomic data which should be > used for display and audit purposes. > > Even though openEHR support an indicator for is_normal this still > stops short of lab data provided in HL7 messages. The abnormal flag > in HL7 lab results is coded with values such as L, H, LL, HH, N, A, > AA, etc indicating more than not normal but which direction and the > degree of abnormality. When transforming this source data into > openEHR we loose this additional information about abnormality. Heath, the obvious question here is: how standardised are these letters and their meanings? Can we assume that all labs the attach "HH" to a serum sodium mean that the value is in the same sub-range? If not, this kind of data is not useful for longitudinal queries into the EHR, since a query for serum sodium with "HH" normal indicator would not have a consistent meaning or result.
If standards don't exist for these flags, then they would need to be created - you can imagine that for the hundreds of pathology tests possible, defining the subranges corresponding to L, H, LL, etc would be a huge amount of work! And current normal ranges are getting revised all the time anyway (people getting taller, heavier, etc). I take the point that physicians don't in general want to see data from the lab removed, but I would like to hear from pathologists & physicians on how they would see this kind of thing being used, standardised, and working in a longitudinal record whose contents are derived from all over the place. - thomas
