ICU Scoring Systems

Reviewed and revised 20 July 2016

OVERVIEW

Scoring systems commonly used in ICU

• GCS = Glasgow Coma Score in Coma
• TISS = Therapeutic Interventions Scoring System
• APACHE = Acute Physiology, Age and Chronic Health Evaluation Systems
• SAPS = Simplified Acute Physiology Score
• MPM = Mortality Prediction Models
• POSSUM = Physiological and Operative Severity Score for the enumeration of Mortality and Morbidity
• SOFA = Sequential Organ Failure Assessment
• also disease/ patient group specific scoring systems such as EuroSCORE (CABG), MELD score (liver failure), etc

Uses

1. compare observed and predicted outcomes for patients
2. stratification of patients for clinical trials
3. assess ICU performance, relative to other ICUs and changes over time
4. predict mortality, prognosis and length of stay for individuals and groups
5. relating resource allocation to severity at presentation

Features

• most measure physiological variables
• some measure interventions
• derived from logistic regression from large demographic data sets

IDEAL SCORING SYSTEM

The ideal scoring system should have the following characteristics :

1. Scores calculated on the basis of easily / routinely recordable variables
2. Well calibrated and validated
3. A high level of discrimination
4. Applicable to all patient populations in ICU
5. Can be used in different countries, health systems or patient cohorts
6. The ability to predict mortality, functional status or quality of life after ICU discharge

Also:

• considers co-morbidities
• considers organisational aspects
• provides a common language for discussion
• method to evaluate critical care practice and process
• allows ability to compare groups in clinical trials

APPLICATION OF SCORING SYSTEMS

Standardised mortality ratio (SMR)

• is the comparison of predicted with observed mortality rates
• need to be considered in the context of case mix and calibration

Description of Case Mix

• stratification of patients for clinical trials
• comparison of predicted and observed outcomes
• allows prediction of resources to manage severity of illness at presentation
• predict length of stay

Problems of Using Severity of Illness Scores to compare outcomes between ICUs

• often done
• problems revolve around: quality of data, appropriateness of model and disease categories
• specific problems:

1. Variation in recording of data (timing, criteria) -> ideally should be audited and reviewed regularly by trained personnel.
2. Differences in patient populations not accounting for by the diagnostic groups.
3. Multiple organ involvement leads to difficult categorisation of disease.
4. Corrupted data, missed data – lack of trained data collectors.
5. Bias or fraud due competition for funding.
6. Historical variations, comparing data across time.
7. Outcomes may be dependent on not only ICU management, but the whole hospital package, surgeon, radiology…

EXAMPLES OF SCORING SYSTEMS

Glasgow Coma Scale (GCS)

• EVM scores
• provides systematic way of assessing the head injured
• directs investigation and therapy
• affected by alcohol and sedation
• used in APACHE II
• useful in prognostication

Therapeutic Intervention Scoring System (TISS)

• developed to: estimate severity of illness and quantify burden of work for ICU staff
• daily collection of 76 items (interventions and treatments)
• good indicator of nursing and medical work
• poor measure of severity of illness
• less widely used
• can be used as an allocation of resources (accountancy) tool

Acute Physiology, Age, and Chronic Health Evaluation Systems (APACHE I-IV)

• I – 1987
• II – 1985 (most widely used in the world, 12 variables, score of 0-71, worse values in first 24 hours in ICU, limited by derivation from an historical data set)
• III – 1991 (score of 0-299, 16 variables, improved prognostication, improved discrimination and calibration)
• IV – 2006 (large data set, more variables included, more accurate, only used in US)

Simplified Acute Physiology Score (SAPS 1-3)

• SAPS 1 (French ICU’s, solely looked at physiology)
• SAPS 2 (1993, European and North American, added chronic health conditions, greater calibration and discrimination)
• SAPS 3 (2005, around the world, 20 variables – prior to admission, at admission, acute physiological derangement)

Mortality Prediction Model I (MPM I)

• variables at admission and during first 24 hours
• computes a hospital risk of death from the absence or presence of factors in a logistic regression equation

Mortality Prediction Model II (MPM II)

• based on the same data set as SAPS II
• outcome prediction at 24, 48 and 72 hrs

POSSUM

• 1991
• 12 acute physiological parameters (surgery and severity of surgery)
• useful tool for surgeons who needed a risk adjustment tool
• meant to predict death but was found to over predict.
• P-POSSUM – Portsmouth: predicts hospital mortality more accurately
• V-POSSUM – vascular surgery
• Cr-POSSUM – colon cancer resection

Sequential Organ Failure Assessment (SOFA)

• 6 organs and grades organ function
• simple and take into account supportive treatments
• good way of tracking patient morbidity
• often used to analyse secondary endpoints in research trials

References and Links

LITFL

• CCC — APACHE Versus SOFA Scoring Systems
• CCC — Glasgow Coma Scale (GCS)

Journal articles

• Breslow MJ, Badawi O. Severity scoring in the critically ill: part 1–interpretation and accuracy of outcome prediction scoring systems. Chest. 2012 Jan;141(1):245-52. PMID: 22215834.
• Breslow MJ, Badawi O. Severity scoring in the critically ill: part 2: maximizing value from outcome prediction scoring systems. Chest. 2012 Feb;141(2):518-27. PMID: 22315120.
• Vincent JL, Moreno R. Clinical review: scoring systems in the critically ill. Critical care (London, England). 14(2):207. 2010. PMC2887099