{
  "resourceType": "CodeSystem",
  "status": "draft",
  "content": "fragment",
  "name": "NexusObsCS",
  "id": "nexus-obs",
  "title": "Observation Code CodeSystem",
  "description": "Local observation codes for clinical instruments that a decision-support criterion has to match\nexactly.\n\n**For a scored instrument, written alongside a standard code rather than instead of one.** Those\nObservations carry their SNOMED CT concept as well; the local code exists because the nearest\nstandard codes do not identify the instrument precisely enough for a threshold to be safe. The\nclearest case: the modified MRC dyspnoea scale runs 0 to 4 and the original MRC scale runs 1 to 5,\nthey overlap on 1 to 4, and a criterion bound to the wrong one is off by a grade with nothing to\ncatch it. The recorded reviews here carry the local code alone -- there is no measurement to code,\nonly the fact that the review happened and when.\n\n**The codes include a `nexus-obs:` prefix as part of the value.** `nexus-obs:mmrc-grade` is the\ncode; `mmrc-grade` is not. Match the full string.\n\n⚠ **A separate system spells three of these codes without the prefix.** `cat-total-score`,\n`mmrc-grade` and `inhaler-technique` are also carried under\n`http://services.well.com/fhir/provisional/CodeSystem/nexus-obs` with bare codes; `copd-action-plan`\nis not. That URI is not this one, is not declared here, and differs in both the system and the code,\nso neither matches across. No application writes it -- data reaches a store under it through seeded\nreference data -- but a store that holds that data holds both spellings at once rather than one\nsucceeding the other. A consumer reading both must match both pairs explicitly.\n\n**Content is a fragment.** Membership is minted by care-package and criteria content on its own\ncadence, so a code absent from this list may still be in the system. Bind extensible.",
  "url": "https://fhir.apps.health/CodeSystem/nexus-obs",
  "concept": [
    {
      "code": "nexus-obs:cat-total-score",
      "display": "CAT total score",
      "definition": "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 on the same Observation. Carries neither the `laboratory` nor the `vital-signs` category -- it is a questionnaire total -- so a criterion cannot narrow to it by category."
    },
    {
      "code": "nexus-obs:mmrc-grade",
      "display": "mMRC dyspnoea grade",
      "definition": "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 the original MRC breathlessness scale, which runs 1 to 5 and is `450755002` in SNOMED CT and 98070-6 in LOINC: the two are off by one across the range and overlap on 1 to 4, so a grade alone cannot tell them apart."
    },
    {
      "code": "nexus-obs:inhaler-technique",
      "display": "Inhaler technique",
      "definition": "A review of the patient's inhaler technique, recorded as a chart event rather than a measurement."
    },
    {
      "code": "nexus-obs:copd-action-plan",
      "display": "COPD action plan given or reviewed",
      "definition": "A COPD self-management action plan given to the patient or reviewed with them, recorded as a chart event rather than a measurement."
    }
  ],
  "experimental": false,
  "caseSensitive": true
}