This is a great topic and I would like to know what people think. Basically, if I need to know average weight for each month if I am studying obesity (or average LDL cholesterol, or eGFR), there may be multiple LOINC codes contributing to my aggregated view of a given lab parameter (weight). (weight measured-by-nurse-in-office vs. weight self-reported )
PCORNet aggregates several LOINC into their "nice lab data row" but it would be nice to be able to do it (in OMOP) with R package or OMOP standardized query. I would point the method to a high level LOINC concept (weight), and it would support some smart aggregation.