I'm fine with the split between Observation and Measurement as it represents a differentiation between quality, trustworthiness and use of specialized equipment and techniques. Perhaps the names are getting in the way? I think of Measurement as "assay"/"analysis" and Observation as "examination"/"response".
It also seems that units can provide some guidance here. I could reasonably expect the observation of gross values (kg/cm/Likert/dates), but not fine values (mmol/L, mmHG, # cells per HPF).
Following this approach, patient provenance measurements seems odd...
- Weight / height: lbs/kg/in/cm: Observations
- Medical history: Patient provided: Observations
- Survey response: Patient provided: Observations
- Dietary recall: Patient provided: Observations
- Bone Density: Obtained from imaging inside of body using specialized equipment: Measurement
- Ejection fraction: Obtained from imaging inside of body using specialized equipment: Measurement
- Urine appearance: Obtained from specimen, evaluated by clinical staff: Measurement
- Hematocrit: Obtained from specimen using specialized equipment, mm/dL: Measurement
- BP: Obtained using specialized equipment, mmHG: Measurement
- Heart Rate: Obtained using specialized equipment: Measurement
- Blood sugar from lab specimen: Obtained from specimen, performed by clinical staff, mmol/L: Measurement
- Blood sugar from patient monitor: Obtained from specimen, performed and reported by patient, mmol/L: ???
My main issue with processing Survey/History data into observation has been conceptually mapping questions and responses. This is mainly because the CRFs were not developed with thought of the available biomedical terminologies. There are many questions that can almost be mapped, but were written in negated form ("I have never has heart problems: T/F". "Birth Weight Unknown: T/F"). Also, the Observation table ends up containing condition, procedure... that cannot be mapped to a term in the Observation class.