admissions table

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.

Links to

• patients on subject_id

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.

Table columns

Name	Postgres data type
subject_id	INTEGER NOT NULL
hadm_id	INTEGER NOT NULL
admittime	TIMESTAMP NOT NULL
dischtime	TIMESTAMP
deathtime	TIMESTAMP
admission_type	VARCHAR(40) NOT NULL
admit_provider_id	VARCHAR(10)
admission_location	VARCHAR(60)
discharge_location	VARCHAR(60)
insurance	VARCHAR(255)
language	VARCHAR(10)
marital_status	VARCHAR(30)
race	VARCHAR(80)
edregtime	TIMESTAMP
edouttime	TIMESTAMP
hospital_expire_flag	SMALLINT

Detailed description

The admissions table defines all hospitalizations in the database. Hospitalizations are assigned a unique random integer known as the hadm_id.

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 2000000 - 2999999. 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 is useful for classifying the urgency of the admission. There are 9 possibilities: ‘AMBULATORY OBSERVATION’, ‘DIRECT EMER.’, ‘DIRECT OBSERVATION’, ‘ELECTIVE’, ‘EU OBSERVATION’, ‘EW EMER.’, ‘OBSERVATION ADMIT’, ‘SURGICAL SAME DAY ADMISSION’, ‘URGENT’.

admit_provider_id

admit_provider_id provides an anonymous identifier for the provider who admitted the patient. Provider identifiers follow a consistent pattern: the letter “P”, followed by either three numbers, followed by two letters or two numbers. For example, “P003AB”, “P00102”, “P1248B”, etc. Provider identifiers are randomly generated and do not have any inherent meaning aside from uniquely identifying the same provider across the database.

admission_location, discharge_location

admission_location provides information about the location of the patient prior to arriving at the hospital. Note that as the emergency room is technically a clinic, patients who are admitted via the emergency room usually have it as their admission location.

Similarly, discharge_location is the disposition of the patient after they are discharged from the hospital.

Association with UB-04 billing codes

admission_location and discharge_location are associated with internal hospital ibax codes which aren’t provided in MIMIC-IV. These internal codes tend to align with UB-04 billing codes.

In some cases more than one internal code is associated with a given admission_location and discharge_location. This can either be do to; 1) multiple codes being used by the hospital for the same admission_location or discharge_location, or 2) during de-identification multiple internal codes may be combined into a single admission_location or discharge_location.

In the tables below, we provide the matching UB-04 code(s) for the most common ibax codes for a given admission_location and discharge_location, when applicable. In cases where more than one code is given, if this combination is due to 1) in the above paragraph, the additional code must have at least 10% of the entires of the most common code.

Admission UB-04 mappings:

admission_location	UB-04 code(s)
PHYSICIAN REFERRAL	1, 3
WALK-IN/SELF REFERRAL	1
AMBULATORY SURGERY TRANSFER	1, 2, 6
INFORMATION NOT AVAILABLE	1, 9
CLINIC REFERRAL	2, 8
PROCEDURE SITE	2
PACU	2
TRANSFER FROM HOSPITAL	4, 6
TRANSFER FROM SKILLED NURSING FACILITY	5
EMERGENCY ROOM	1, 2, 7
INTERNAL TRANSFER TO OR FROM PSYCH	none

Discharge UB-04 mappings:

discharge_location	UB-04 code(s)
HOME	01
ACUTE HOSPITAL	02, 81, 86
SKILLED NURSING FACILITY	03, 64
ASSISTED LIVING	04
HEALTHCARE FACILITY	05, 43
HOME HEALTH CARE	06
AGAINST ADVICE	07
DIED	20
OTHER FACILITY	21, 70
HOSPICE	50, 51
REHAB	62
CHRONIC/LONG TERM ACUTE CARE	63
PSYCH FACILITY	65
OTHER FACILITY	70

UB-04 documentation online often provides more detail than found in the admission_location and discharge_location text, particularly for discharges.

insurance, language, marital_status, ethnicity

The insurance, language, marital_status, and ethnicity columns provide information about patient demographics for the given hospitalization. Note that as this data is documented for each hospital admission, they may change from stay to stay.

edregtime, edouttime

The date and time at which the patient was registered and discharged from the emergency department.

hospital_expire_flag

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