The admissions table

Table source: Hospital database.

Table purpose: Define a patient’s hospital admission, HADM_ID.

Number of rows: 58976

Links to:

• PATIENTS on SUBJECT_ID

Brief summary

The ADMISSIONS table gives information regarding a patient’s admission to the hospital. Since each unique hospital visit for a patient is assigned a unique HADM_ID, the ADMISSIONS table can be considered as a definition table for HADM_ID. Information available includes timing information for admission and discharge, demographic information, the source of the admission, and so on.

Important considerations

• The data is sourced from the admission, discharge and transfer database from the hospital (often referred to as ‘ADT’ data).
• Organ donor accounts are sometimes created for patients who died in the hospital. These are distinct hospital admissions with very short, sometimes negative lengths of stay. Furthermore, their DEATHTIME is frequently the same as the earlier patient admission’s DEATHTIME.
• All text data, except for that in the INSURANCE column, is stored in upper case.

Table columns

Name	Postgres data type
ROW_ID	INT
SUBJECT_ID	INT
HADM_ID	INT
ADMITTIME	TIMESTAMP(0)
DISCHTIME	TIMESTAMP(0)
DEATHTIME	TIMESTAMP(0)
ADMISSION_TYPE	VARCHAR(50)
ADMISSION_LOCATION	VARCHAR(50)
DISCHARGE_LOCATION	VARCHAR(50)
INSURANCE	VARCHAR(255)
LANGUAGE	VARCHAR(10)
RELIGION	VARCHAR(50)
MARITAL_STATUS	VARCHAR(50)
ETHNICITY	VARCHAR(200)
EDREGTIME	TIMESTAMP(0)
EDOUTTIME	TIMESTAMP(0)
DIAGNOSIS	VARCHAR(300)
HOSPITAL_EXPIRE_FLAG	TINYINT
HAS_CHARTEVENTS_DATA	TINYINT

Detailed description

The ADMISSIONS table defines all HADM_ID present in the database, covering an admission period between 1 June 2001 and 10 October 2012.

SUBJECT_ID, HADM_ID

Each row of this table contains a unique HADM_ID, which represents a single patient’s admission to the hospital. HADM_ID ranges from 1000000 - 1999999. It is possible for this table to have duplicate SUBJECT_ID, indicating that a single patient had multiple admissions to the hospital. The ADMISSIONS table can be linked to the PATIENTS table using SUBJECT_ID.

ADMITTIME, DISCHTIME, DEATHTIME

ADMITTIME provides the date and time the patient was admitted to the hospital, while DISCHTIME provides the date and time the patient was discharged from the hospital. If applicable, DEATHTIME provides the time of in-hospital death for the patient. Note that DEATHTIME is only present if the patient died in-hospital, and is almost always the same as the patient’s DISCHTIME. However, there can be some discrepancies due to typographical errors.

ADMISSION_TYPE

ADMISSION_TYPE describes the type of the admission: ‘ELECTIVE’, ‘URGENT’, ‘NEWBORN’ or ‘EMERGENCY’. Emergency/urgent indicate unplanned medical care, and are often collapsed into a single category in studies. Elective indicates a previously planned hospital admission. Newborn indicates that the HADM_ID pertains to the patient’s birth.

ADMISSION_LOCATION

ADMISSION_LOCATION provides information about the previous location of the patient prior to arriving at the hospital. There are 9 possible values:

• EMERGENCY ROOM ADMIT
• TRANSFER FROM HOSP/EXTRAM
• TRANSFER FROM OTHER HEALT
• CLINIC REFERRAL/PREMATURE
• ** INFO NOT AVAILABLE **
• TRANSFER FROM SKILLED NUR
• TRSF WITHIN THIS FACILITY
• HMO REFERRAL/SICK
• PHYS REFERRAL/NORMAL DELI

The truncated text occurs in the raw data.

INSURANCE, LANGUAGE, RELIGION, MARITAL_STATUS, ETHNICITY

The INSURANCE, LANGUAGE, RELIGION, MARITAL_STATUS, ETHNICITY columns describe patient demographics. These columns occur in the ADMISSIONS table as they are originally sourced from the admission, discharge, and transfers (ADT) data from the hospital database. The values occasionally change between hospital admissions (HADM_ID) for a single patient (SUBJECT_ID). This is reasonable for some fields (e.g. MARITAL_STATUS, RELIGION), but less reasonable for others (e.g. ETHNICITY).

EDREGTIME, EDOUTTIME

Time that the patient was registered and discharged from the emergency department.

DIAGNOSIS

The DIAGNOSIS column provides a preliminary, free text diagnosis for the patient on hospital admission. The diagnosis is usually assigned by the admitting clinician and does not use a systematic ontology. As of MIMIC-III v1.0 there were 15,693 distinct diagnoses for 58,976 admissions. The diagnoses can be very informative (e.g. chronic kidney failure) or quite vague (e.g. weakness). Final diagnoses for a patient’s hospital stay are coded on discharge and can be found in the DIAGNOSES_ICD table. While this field can provide information about the status of a patient on hospital admission, it is not recommended to use it to stratify patients.

HOSPITAL_EXPIRE_FLAG

This indicates whether the patient died within the given hospitalization. 1 indicates death in the hospital, and 0 indicates survival to hospital discharge.