Measurement

Epic equivalent: Clarity lab results / Flowsheet vitals / Observation results

The measurement table captures structured numeric and categorical test results — lab values, vital signs, imaging reads, and clinical assessments. In Epic, these live in separate places: lab results in one module, flowsheet vitals in another, some observations in yet another. In OMOP, they all land in this single table.

Each row is a single measurement event (one A1c result, one blood pressure reading, one creatinine value).

Epic-to-OMOP Field Mapping

Field reference (click to expand)

OMOP Field	Epic Equivalent	What It Captures
measurement_id	Result ID	Unique identifier for the measurement
person_id	Patient ID / MRN	Links to the patient
measurement_concept_id	LOINC / test concept	Standardized test (e.g., "Hemoglobin A1c", "Systolic BP"). Use this for analysis
measurement_date	Result date	When the measurement was taken; measurement_datetime has time precision
measurement_type_concept_id	Data provenance	Whether from EHR, lab feed, patient-reported, etc.
value_as_number	Numeric result	The test value (e.g., 6.2 for A1c, 120 for systolic BP)
value_as_concept_id	Categorical result	For results like "Positive", "Negative", "Detected"
unit_concept_id	Unit of measurement	Standardized unit (mg/dL, mmHg, etc.)
range_low, range_high	Reference range	Normal range for the test
provider_id	Ordering provider	Who ordered or recorded the result
visit_occurrence_id	Linked encounter	Visit associated with the measurement
measurement_source_value	Local test name	Original value from the source system
unit_source_value	Local unit	Original unit as recorded in the EHR

What to Watch For

Common pitfalls

Labs and vitals share the same table

Blood pressure and hemoglobin are neighbors. Always filter by measurement_concept_id — don't assume all rows are lab results.

Unit inconsistencies

Not all sites standardize units perfectly. Always check unit_concept_id and be cautious comparing values across different unit mappings.

Categorical vs. numeric results

Some tests (COVID PCR, pregnancy tests) use value_as_concept_id instead of value_as_number. Check both when querying.

Research Patterns

Question	Tables Involved
Average A1c among diabetes patients	measurement (A1c concept) + condition_occurrence (diabetes)
Low hemoglobin prior to surgery	measurement (Hgb concept + value threshold) + procedure_occurrence
Creatinine trends over time in CKD patients	measurement (creatinine concept) + condition_occurrence (CKD)
Positive COVID-19 PCR tests in the ER	measurement.value_as_concept_id (Positive) + visit_occurrence (ER)
Uncontrolled systolic BP in hypertension	measurement (systolic BP concept + value > 140) + condition_occurrence (hypertension)