OMOP Primers — The Epic-to-OMOP Bridge
You know Epic. You've queried Clarity, built reports from Caboodle, or pulled data from the CDW. OMOP organizes the same clinical data differently — and once you see the mapping, it clicks fast.
How to use these primers
Each primer page maps familiar EHR concepts (Clarity tables, encounter types, order entries) to their OMOP equivalents. Start with When to Use OMOP if you're deciding whether OMOP fits your project, or jump straight to a table below.
The Key Shift: Encounters vs. Patients
In Epic, most data is organized around encounters — an office visit, an ED arrival, an admission. You navigate from the encounter to the patient's orders, results, and diagnoses.
In OMOP, data is organized around patients. The person table is the center of the universe. Visits, conditions, drugs, measurements, and procedures all link back to person_id. Encounters still exist (visit_occurrence), but they're one of many tables hanging off the patient — not the organizing spine.
graph LR
A[person] --> B[visit_occurrence]
A --> C[condition_occurrence]
A --> D[drug_exposure]
A --> E[measurement]
A --> F[procedure_occurrence]
A --> G[observation]
B -.-> C
B -.-> D
B -.-> E
B -.-> FQuick Orientation
| If you're used to this in Epic... | ...look here in OMOP |
|---|---|
| Patient demographics (MRN, DOB, sex, race) | person |
| Encounters / ADT | visit_occurrence + visit_detail |
| Encounter diagnoses, problem list | condition_occurrence |
| Medication orders, MAR | drug_exposure |
| Lab results, flowsheet vitals | measurement |
| Procedures, surgical cases, imaging orders | procedure_occurrence |
| Clinical notes, discharge summaries | note + note_nlp |
| Questionnaires, social history, smoking status | observation |
| ICD-10, CPT, SNOMED, RxNorm, LOINC codes | Standardized Vocabularies |
Explore by Category
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Clinical Data
The core patient-level tables: conditions, drugs, measurements, procedures, visits, observations, notes, devices, specimens, and more.
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Health System
Where care happens and who provides it: locations, care sites, and providers.
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Vocabularies
The mapping layer that makes OMOP work — how ICD, CPT, NDC, and local codes translate to standard concepts.
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Health Economics
Cost and payer plan data. Sparse in EHR-derived OMOP (including Emory) but important for claims-linked studies.
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When to Use OMOP
Decision guide: when OMOP is the right choice over Clarity, Caboodle, or the Reporting Workbench — and when it isn't.
New to OMOP entirely?
Start with our Training page — the Basic Pathway takes about an hour and covers the CDM fundamentals. Then come back here to see how it maps to what you already know from Epic.
The CDM at a Glance
The diagram below shows all OMOP CDM v5.4 tables, color-coded by category. Our primers cover the tables most relevant to Emory researchers.
