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Medical coding systems are common vocabularies that allow specific identification of different clinical concepts. There are a number of common and widely used medical coding systems, such as ICD-10-CM, SNOMED, and others. However, different healthcare IT systems use all kinds of coding systems - some standardized, some proprietary. Metriport enriches data with code system lookup, normalization, and cross-walks, so that the result is cohesive and more robust than it is at the source.

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Common Medical Coding Systems

You can use the URLs of these systems from the table below to filter for relevant codes in your patient’s Consolidated Bundle.
Below is an overview of the most prevalent coding systems supported by Metriport and often found in the source documents:
Coding SystemIdentifiersPurposeFHIR ResourcesExampleMaintained by
ICD-10-CM
(International Classification of Diseases, 10th Revision, Clinical Modification)		OID: 2.16.840.1.113883.6.90
URL: http://hl7.org/fhir/sid/icd-10-cm		Encodes medical diagnoses and conditionsConditionE11.9 → Type 2 diabetes mellitus without complicationsU.S. National Center for Health Statistics (NCHS)
CPT
(Current Procedural Terminology)		OID: 2.16.840.1.113883.6.12
URL: http://www.ama-assn.org/go/cpt		Encodes outpatient medical procedures and servicesProcedure0331T → Myocardial sympathetic innervation imaging, planar qualitative and quantitative assessmentAmerican Medical Association (AMA)
CVX
(Vaccine Codes)		OID: 2.16.840.1.113883.12.292
URL: http://hl7.org/fhir/sid/cvx		Identifies vaccines and vaccine groupsImmunization125 → Novel Influenza-H1N1-09, live virus for nasal administrationU.S. Centers for Disease Control and Prevention (CDC)
SNOMED CT
(Systematized Nomenclature of Medicine – Clinical Terms)		OID: 2.16.840.1.113883.6.96
URL: http://snomed.info/sct		Encodes comprehensive clinical terminology for conditions, findings, and proceduresCondition, Procedure, and others44054006 → Diabetes mellitus type 2 (disorder)SNOMED International
LOINC
(Logical Observation Identifiers Names and Codes)		OID: 2.16.840.1.113883.6.1
URL: http://loinc.org		Encodes laboratory and clinical observationsObservation, Encounter, and others718-7 → Hemoglobin [Mass/volume] in BloodRegenstrief Institute
NDC
(National Drug Code)		OID: 2.16.840.1.113883.6.69
URL: http://hl7.org/fhir/sid/ndc		Identifies drug products marketed in the U.S.Medication0002-8215-01 → insulin human (Humulin R) 100 [iU]/mL Parenteral Injection, Solution, 1 VIAL, MULTI-DOSE in 1 CARTON (0002-8215-01) / 10 mL in 1 VIAL, MULTI-DOSEU.S. Food and Drug Administration (FDA)
RxNormOID: 2.16.840.1.113883.6.88
URL: http://www.nlm.nih.gov/research/umls/rxnorm		Normalizes drug names and clinical drugsMedication311036 → HumuLIN R 100 UNT/ML Injectable SolutionU.S. National Library of Medicine (NLM)

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Other Clinical Classification Systems

These systems are typically not provided in the source documents, but are added by Metriport:
Coding SystemPurposeFHIR ResourcesExampleMaintained by
CCSR
(Clinical Classifications Software Refined)		Groups ICD-10-CM diagnosis codes into clinically meaningful categories across body systemsConditionEND002 → Diabetes mellitus without complicationU.S. Agency for Healthcare Research and Quality (AHRQ)
HCC
(Hierarchical Condition Categories)		Groups ICD-10-CM diagnosis codes into hierarchical categories used for risk adjustment and reimbursementCondition18 → Diabetes with chronic complicationsU.S. Centers for Medicare & Medicaid Services (CMS)
CCIR
(Chronic Condition Indicator Refined)		Classifies ICD-10-CM diagnosis codes as chronic or nonchronic across 18 clinical condition categoriesConditionC → ChronicU.S. Agency for Healthcare Research and Quality (AHRQ)

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Representation in FHIR

Each of these coding systems appears in FHIR as elements of coding, category, or extension arrays. Here’s a subset of attributes you can expect to find in a Condition resource, displaying how Metriport uses different coding systems to hydrate the clinical data: 
{
  "resourceType": "Condition",
  "code": {
    "text": "Unspecified atrial fibrillation",
    "coding": [
      {
        "code": "I48.91",
        "display": "Unspecified atrial fibrillation",
        "system": "http://hl7.org/fhir/sid/icd-10-cm"
      },
      {
        "code": "49436004",
        "system": "http://snomed.info/sct",
        "display": "Atrial fibrillation (disorder)"
      },
      {
        "code": "427.31",
        "display": "Atrial fibrillation, unspecified type (HCC)",
        "system": "http://terminology.hl7.org/CodeSystem/ICD-9CM-diagnosiscodes"
      }
    ]
  },
  "category": [
    {
      "coding": [
        {
          "system": "http://terminology.hl7.org/CodeSystem/condition-category",
          "code": "encounter-diagnosis",
          "display": "Encounter Diagnosis"
        }
      ],
      "text": "Encounter Diagnosis"
    },
    {
      "coding": [
        {
          "system": "https://hcup-us.ahrq.gov/toolssoftware/ccsr/ccs_refined.jsp",
          "code": "CIR",
          "display": "Diseases of the circulatory system"
        }
      ],
      "text": "Diseases of the circulatory system"
    }
  ],
  "extension": [
    {
      "url": "http://hl7.org/fhir/StructureDefinition/condition-related",
      "valueCoding": {
        "code": "C",
        "display": "Chronic",
        "system": "https://public.metriport.com/fhir/StructureDefinition/condition-chronicity.json"
      }
    },
    {
      "url": "https://public.metriport.com/fhir/StructureDefinition/condition-hcc.json",
      "valueCodeableConcept": {
        "coding": [
          {
            "system": "http://terminology.hl7.org/CodeSystem/cmshcc",
            "display": "Unspecified atrial fibrillation",
            "version": "v24",
            "code": "96"
          }
        ]
      }
    }
  ]
}