Observation Code CodeSystem Code system

Canonical	../CodeSystem/nexus-obs
Status	draft · 1.26.0
Content	fragment
Source	FSH · JSON

Local observation codes for clinical instruments that a decision-support criterion has to match exactly.

For a scored instrument, written alongside a standard code rather than instead of one. Those Observations carry their SNOMED CT concept as well; the local code exists because the nearest standard codes do not identify the instrument precisely enough for a threshold to be safe. The clearest case: the modified MRC dyspnoea scale runs 0 to 4 and the original MRC scale runs 1 to 5, they overlap on 1 to 4, and a criterion bound to the wrong one is off by a grade with nothing to catch it. The recorded reviews here carry the local code alone -- there is no measurement to code, only the fact that the review happened and when.

The codes include a nexus-obs: prefix as part of the value. nexus-obs:mmrc-grade is the code; mmrc-grade is not. Match the full string.

⚠ A separate system spells three of these codes without the prefix. cat-total-score, mmrc-grade and inhaler-technique are also carried under http://services.well.com/fhir/provisional/CodeSystem/nexus-obs with bare codes; copd-action-plan is not. That URI is not this one, is not declared here, and differs in both the system and the code, so neither matches across. No application writes it -- data reaches a store under it through seeded reference data -- but a store that holds that data holds both spellings at once rather than one succeeding the other. A consumer reading both must match both pairs explicitly.

Content is a fragment. Membership is minted by care-package and criteria content on its own cadence, so a code absent from this list may still be in the system. Bind extensible.

Code	Display	Definition
nexus-obs:cat-total-score	CAT total score	The COPD Assessment Test total, an eight-item instrument scored 0 to 40 as a whole number. A threshold outside that range cannot be met. Also coded 57671000052108 in SNOMED CT o…
nexus-obs:mmrc-grade	mMRC dyspnoea grade	The modified Medical Research Council dyspnoea grade, 0 to 4. Also coded 870179002 |modified Medical Research Council Dyspnea Scale| in SNOMED CT on the same Observation. NOT th…
nexus-obs:inhaler-technique	Inhaler technique	A review of the patient's inhaler technique, recorded as a chart event rather than a measurement.
nexus-obs:copd-action-plan	COPD action plan given or reviewed	A COPD self-management action plan given to the patient or reviewed with them, recorded as a chart event rather than a measurement.