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MEASUREMENT table
The MEASUREMENT table contains records of Measurement, i.e. structured values (numerical or categorical) obtained through systematic and standardized examination or testing of a Person or Person's sample. The MEASUREMENT table contains both orders and results of such Measurements as laboratory tests, vital signs, quantitative findings from pathology reports, etc.
| Field | Required | Type | Description |
|---|---|---|---|
| measurement_id | Yes | integer | A unique identifier for each Measurement. |
| person_id | Yes | integer | A foreign key identifier to the Person about whom the measurement was recorded. The demographic details of that Person are stored in the PERSON table. |
| measurement_concept_id | Yes | integer | A foreign key to the standard measurement concept identifier in the Standardized Vocabularies. |
| measurement_date | Yes | date | The date of the Measurement. |
| measurement_time | No | time | The time of the Measurement. |
| measurement_type_concept_id | Yes | integer | A foreign key to the predefined Concept in the Standardized Vocabularies reflecting the provenance from where the Measurement record was recorded. |
| operator_concept_id | No | integer | A foreign key identifier to the predefined Concept in the Standardized Vocabularies reflecting the mathematical operator that is applied to the value_as_number. Operators are <, ≤, =, ≥, >. |
| value_as_number | No | float | A Measurement result where the result is expressed as a numeric value. |
| value_as_concept_id | No | integer | A foreign key to a Measurement result represented as a Concept from the Standardized Vocabularies (e.g., positive/negative, present/absent, low/high, etc.). |
| unit_concept_id | No | integer | A foreign key to a Standard Concept ID of Measurement Units in the Standardized Vocabularies. |
| range_low | No | float | The lower limit of the normal range of the Measurement result. The lower range is assumed to be of the same unit of measure as the Measurement value. |
| range_high | No | float | The upper limit of the normal range of the Measurement. The upper range is assumed to be of the same unit of measure as the Measurement value. |
| provider_id | No | integer | A foreign key to the provider in the PROVIDER table who was responsible for initiating or obtaining the measurement. |
| visit_occurrence_id | No | integer | A foreign key to the Visit in the VISIT_OCCURRENCE table during which the Measurement was recorded. |
| measurement_source_value | No | varchar(50) | The Measurement name as it appears in the source data. This code is mapped to a Standard Concept in the Standardized Vocabularies and the original code is stored here for reference. |
| measurement_source_concept_id | No | integer | A foreign key to a Concept in the Standard Vocabularies that refers to the code used in the source. |
| unit_source_value | No | varchar(50) | The source code for the unit as it appears in the source data. This code is mapped to a standard unit concept in the Standardized Vocabularies and the original code is stored here for reference. |
| value_source_value | No | varchar(50) | The source value associated with the content of the value_as_number or value_as_concept as stored in the source data. |
Conventions
- Measurements differ from Observations in that they require a standardized test or some other activity to generate a quantitative or qualitative result. For example, LOINC 1755-8 concept_id 3027035 'Albumin [Mass/time] in 24 hour Urine' is the lab test to measure a certain chemical in a urine sample.
- Even though each Measurement requires to have a result, the fields value_as_number and value_as_concept_id are not mandatory. When the result is missing, the Measurement record might represent an order or the result was not captured in the source data (missing data).
- Valid Measurement Concepts (measurement_concept_id) belong to the 'Measurement' domain, but could overlap with the 'Observation' domain. This is due to the fact that there is a continuum between systematic examination or testing (Measurement) and a simple determination of fact (Observation).
- Measurements are stored as attribute value pairs, with the attribute as the Measurement Concept and the value representing the result. The value can be a Concept (stored in value_as_concept), or a numerical value (value_as_number) with a Unit (unit_concept_id).
- Valid Concepts for the value_as_concept field belong to the 'Meas Value' domain.
- For some Measurement Concepts, the result is included in the test. For example, SNOMED-CT 71628007 concept_id 4325125 'Abnormal presence of albumin' indicates a Measurement (albumin in sample) and the result (abnormal). In future releases of the Standardized Vocabularies, these will be split into the correct Measurement and result.
- The operator_concept_id is optionally given for relative Measurements where the precise value is not available but its relation to a certain benchmarking value is. For example, this can be used for minimal detection thresholds of a test.
- The meaning of Concept 4172703 for '=' is identical to omission of a operator_concept_id value. Since the use of this field is rare, it's important when devising analyses to not to forget testing for the content of this field for values different from =.
- Valid Concepts for the operator_concept_id field belong to the 'Meas Value Operator' domain.
- The Unit is optional even if a value_as_number is provided.
- If reference ranges for upper and lower limit of normal as provided (typically by a laboratory) these are stored in the range_high and range_low fields. Ranges have the same unit as the value_as_number.
- The Visit during which the observation was made is recorded through a reference to the VISIT_OCCURRENCE table. This information is not always available.
- The Provider making the observation is recorded through a reference to the PROVIDER table. This information is not always available.
documentation/cdm/measurement.1417888017.txt.gz · Last modified: 2014/12/06 17:46 by cgreich
