Track 1 — FHIR Fundamentals

Condition

Condition represents a clinical diagnosis, problem, or finding that is significant enough to be tracked over time. Diabetes type 2, hypertension, a broken leg — all are Conditions in FHIR.

What Condition represents

A Condition is a clinical statement about a patient's health state. It covers diagnoses (confirmed diseases), problems (patient-reported issues), and health concerns. The same underlying concept — a patient has Type 2 diabetes — can have different states: suspected, confirmed, active, in remission, resolved.

Condition is not the same as a symptom or a finding at a single point in time. Those are Observations. A Condition persists: it has an onset, it may evolve, and it closes when resolved or when the patient dies.

The distinction matters for data modelling. A blood glucose measurement = Observation. The diagnosis of diabetes that motivated that measurement = Condition.

Example: Type 2 Diabetes (JSON)

{
  "resourceType": "Condition",
  "id": "condition-diabetes-001",
  "clinicalStatus": {
    "coding": [{
      "system": "http://terminology.hl7.org/CodeSystem/condition-clinical",
      "code": "active"
    }]
  },
  "verificationStatus": {
    "coding": [{
      "system": "http://terminology.hl7.org/CodeSystem/condition-ver-status",
      "code": "confirmed"
    }]
  },
  "category": [{
    "coding": [{
      "system": "http://terminology.hl7.org/CodeSystem/condition-category",
      "code": "encounter-diagnosis"
    }]
  }],
  "code": {
    "coding": [
      {
        "system": "http://snomed.info/sct",
        "code": "44054006",
        "display": "Diabetes mellitus type 2"
      },
      {
        "system": "http://hl7.org/fhir/sid/icd-10",
        "code": "E11",
        "display": "Type 2 diabetes mellitus"
      }
    ]
  },
  "subject": { "reference": "Patient/patient-001" },
  "onsetDateTime": "2018-03-15"
}

The two status fields

Condition has two separate status fields. Both are required. They answer different questions.

clinicalStatus — is the condition currently affecting the patient?

Code	Meaning
active	Currently affecting the patient
recurrence	Has returned after being resolved
relapse	Has worsened after improvement
inactive	No longer active, not fully resolved
remission	Clinically controlled
resolved	Gone, no longer present

verificationStatus — how certain is this diagnosis?

Code	Meaning
unconfirmed	Not yet confirmed
provisional	Working hypothesis, differential
differential	One of several possible diagnoses
confirmed	Confirmed by appropriate criteria
refuted	Ruled out
entered-in-error	Recorded by mistake

Coding: SNOMED CT and ICD-10

The code element specifies what the condition is. FHIR allows multiple codings — the same condition coded in both SNOMED CT (for clinical precision) and ICD-10 (for billing and reporting) in parallel.

SNOMED CT

System: http://snomed.info/sct

Code: 44054006

Purpose: clinical precision, concept hierarchy

ICD-10

System: http://hl7.org/fhir/sid/icd-10

Code: E11

Purpose: billing, epidemiology, reporting

Onset and abatement

Condition tracks the lifecycle of a diagnosis over time. Both fields are polymorphic — they can be a date, a date-time, a period, or a descriptive string.

onset[x]When the condition started. onsetDateTime, onsetAge, onsetPeriod, onsetRange, onsetString.

abatement[x]When the condition ended or resolved. Only present if clinicalStatus is inactive/remission/resolved.