The labevents table

Table source: Hospital database.

Table purpose: Contains all laboratory measurements for a given patient, including out patient data.

Number of rows: 27,854,055

Links to:

• PATIENTS on SUBJECT_ID
• ADMISSIONS on HADM_ID
• D_LABITEMS on ITEMID

Brief summary

The LABEVENTS data contains information regarding laboratory based measurements. The process for acquiring a lab measurement is as follows: first, a member of the clinical staff acquires a fluid from a site in the patient’s body (e.g. blood from an arterial line, urine from a catheter, etc). Next, the fluid is bar coded to associate it with the patient and timestamped to record the time of the fluid acquisition. The lab analyses the data and returns a result within 4-12 hours.

Important considerations

• Note that the time associated with this result is the time of the fluid acquisition, not the time that the values were made available to the clinical staff.
• The labevents table contains both in-hospital laboratory measurements and out of hospital laboratory measurements from clinics which the patient has visited (since the patient is not “in” a hospital when visiting a clinic, these patients often referred to as “outpatients” and the data is often called “outpatient” data). Laboratory measurements for outpatients do not have a HADM_ID.
• In MIMIC-III v1.0, there is a subset of patients for which the outpatient lab data is not available. They can be identified by checking for patients whose data always has an HADM_ID.
• In MIMIC-III v1.0, there is a subset of patients for which text laboratory data is missing. This primarily affects the blood gas type recorded with blood gases.
• Some items are duplicated between the labevents and chartevents tables. In cases where there is disagreement between measurements, labevents should be taken as the ground truth.

Table columns

Name	Postgres data type
ROW_ID	INT
SUBJECT_ID	INT
HADM_ID	INT
ITEMID	INT
CHARTTIME	TIMESTAMP(0)
VALUE	VARCHAR(200)
VALUENUM	DOUBLE PRECISION
VALUEUOM	VARCHAR(20)
FLAG	VARCHAR(20)

Detailed Description

SUBJECT_ID, HADM_ID

Identifiers which specify the patient: SUBJECT_ID is unique to a patient and HADM_ID is unique to a patient hospital stay.

ITEMID

Identifier for a single measurement type in the database. Each row associated with one ITEMID (e.g. 212) corresponds to an instantiation of the same measurement (e.g. heart rate).

CHARTTIME

CHARTTIME records the time at which an observation was charted, and is usually the closest proxy to the time the data was actually measured. Note that because the data is directly sourced from the laboratory database, it is not validated by ICU clinical staff, and as a result there is no associated STORETIME.

VALUE, VALUENUM

VALUE contains the value measured for the concept identified by the ITEMID. If this value is numeric, then VALUENUM contains the same data in a numeric format. If this data is not numeric, VALUENUM is null. In some cases (e.g. scores like Glasgow Coma Scale, Richmond Sedation Agitation Scale and Code Status), VALUENUM contains the score and VALUE contains the score and text describing the meaning of the score.

VALUEUOM

VALUEUOM is the unit of measurement for the VALUE, if appropriate.

FLAG

FLAG indicates whether the laboratory value is considered abnormal or not, using pre-defined thresholds.