Question For Applying $lastn to Category for Lab results in BgZ Specification

Hi,

Related to MM-1433 - the BgZ on FHIR specification currently lists that for lab results we should return:

GET [base]/Observation/$lastn?category=http://snomed.info/sct|275711006&_include=Observation:related-target&_include=Observation:specimen

Is it intended that we truly only return the last version for a given test that was performed by the Clinical Chemistry laboratory specifically?

As a simple example - the clinical chemistry and microbiology departments of some of our hospitals may both perform Covid testing. 

If a patient has had Covid testing done by both departments according to the below:

• Result 1: November 1 - Clinical Chemistry Department tests and patient is negative
• Result 2: November 25 - Microbiology tests for Covid and patient is negative

Which result do we wish to return? Should that be only the Clinical Chemistry department's test?