MIMIC-IV to eICU Mapping

This skill maps equivalent tables, columns, and concepts between MIMIC-IV and eICU databases to enable cross-database research and external validation.

When to Use This Skill

• External validation of MIMIC-IV models on eICU
• Multi-center studies combining both databases
• Understanding structural differences
• Translating queries between databases

Database Overview

| Characteristic | MIMIC-IV | eICU | |---------------|----------|------| | Institution | Beth Israel Deaconess (single center) | 208 hospitals (multi-center) | | Patients | ~300,000 admissions | ~200,000 patients | | Time Period | 2008-2019 | 2014-2015 | | ICU Types | All ICU types | All ICU types | | Geography | Boston, MA | United States (nationwide) |

Identifier Mapping

| Concept | MIMIC-IV | eICU | |---------|----------|------| | Patient ID | subject_id | uniquepid | | Hospital Admission | hadm_id | patienthealthsystemstayid | | ICU Stay | stay_id | patientunitstayid | | Hospital ID | N/A (single center) | hospitalid | | Unit Visit | icustay_seq | unitvisitnumber |

Core Table Mapping

Patient Demographics

| MIMIC-IV | eICU | Notes | |----------|------|-------| | mimiciv_hosp.patients | patient | Base demographics | | mimiciv_hosp.admissions | patient | Admission info combined | | mimiciv_icu.icustays | patient | ICU stay info in patient table | | mimiciv_derived.icustay_detail | icustay_detail (concept) | Derived convenience table |

Vital Signs

| MIMIC-IV | eICU | Notes | |----------|------|-------| | mimiciv_derived.vitalsign | vitalperiodic, vitalaperiodic | eICU splits periodic/aperiodic | | mimiciv_icu.chartevents | nursecharting | Raw charted values |

Laboratory Values

| MIMIC-IV | eICU | Notes | |----------|------|-------| | mimiciv_hosp.labevents | lab | Different labname conventions | | mimiciv_derived.chemistry | pivoted_lab (concept) | Derived/pivoted | | mimiciv_derived.complete_blood_count | pivoted_lab (concept) | |

Medications

| MIMIC-IV | eICU | Notes | |----------|------|-------| | mimiciv_hosp.prescriptions | medication | Hospital medications | | mimiciv_icu.inputevents | infusiondrug | IV infusions | | mimiciv_derived.antibiotic | - | Concept needs creation for eICU |

Diagnoses

| MIMIC-IV | eICU | Notes | |----------|------|-------| | mimiciv_hosp.diagnoses_icd | diagnosis | eICU uses text descriptions | | - | admissiondx | eICU has admission diagnosis | | - | apacheapsvar | APACHE diagnosis categories |

Concept Availability

Available in Both (May Require Recalculation)

| Concept | MIMIC-IV | eICU | |---------|----------|------| | SOFA | mimiciv_derived.sofa | Requires custom calculation | | APACHE IV | Not pre-computed | apachepatientresult | | OASIS | mimiciv_derived.oasis | pivoted_oasis (concept) | | GCS | mimiciv_derived.gcs | pivoted_score (concept) | | Urine Output | mimiciv_derived.urine_output | pivoted_uo (concept) |

MIMIC-IV Only

• Waveform data (vital sign waveforms)
• Radiology reports
• Detailed microbiology (organism/sensitivity)
• ED data

eICU Only

• APACHE IV scores (pre-computed)
• Multi-center hospital data
• Respiratory care plan documentation
• Nurse care plan

Key Structural Differences

1. Time Representation

MIMIC-IV: Absolute timestamps (DATETIME)
eICU: Offset in minutes from unit admission (INTEGER)

-- MIMIC-IV
WHERE charttime BETWEEN ie.intime AND ie.outtime

-- eICU (convert offset to time)
WHERE chartoffset >= 0 AND chartoffset <= unitdischargeoffset

2. Hospital Structure

MIMIC-IV: Single hospital, no hospital identifier
eICU: hospitalid links to hospital table with region, bed count

3. Diagnosis Coding

MIMIC-IV: ICD-9 and ICD-10 codes
eICU: Free-text diagnosis strings + APACHE categories

4. Lab Value Names

MIMIC-IV: itemid (numeric codes) with d_labitems lookup
eICU: labname (text strings), less standardized

Example: Equivalent Queries

First ICU Stay Selection

MIMIC-IV:

SELECT *
FROM mimiciv_derived.icustay_detail
WHERE first_icu_stay = TRUE;

eICU:

SELECT *
FROM patient
WHERE unitvisitnumber = 1;

Mortality Outcome

MIMIC-IV:

SELECT stay_id, hospital_expire_flag
FROM mimiciv_hosp.admissions a
INNER JOIN mimiciv_icu.icustays ie ON a.hadm_id = ie.hadm_id;

eICU:

SELECT patientunitstayid,
       CASE WHEN hospitaldischargestatus = 'Expired' THEN 1 ELSE 0 END AS hosp_mort
FROM patient;

Age

MIMIC-IV:

SELECT stay_id, admission_age
FROM mimiciv_derived.icustay_detail;
-- Note: Ages > 89 are shifted

eICU:

SELECT patientunitstayid,
       CASE WHEN age = '> 89' THEN 90 ELSE CAST(age AS INT) END AS age
FROM patient;
-- Note: age is stored as string, "> 89" for elderly

Validation Considerations

1. Population Differences: eICU is multi-center with different case-mix
2. Time Period: Different years may have different practices
3. Documentation Patterns: Single vs multi-center charting variability
4. Missing Data: Different missingness patterns
5. Outcome Definitions: Verify mortality/LOS definitions match

References

• Johnson AEW et al. "MIMIC-IV, a freely accessible electronic health record dataset." Scientific Data. 2023.
• Pollard TJ et al. "The eICU Collaborative Research Database." Scientific Data. 2018.