Table 1

Characteristics and Application of the Most Commonly Studied Multimorbidity Measures in Outpatient Settings

MeasureOriginal Derivation/Validation PopulationsInformation NeededOriginal Purpose of ScoreHow Information Is UsedComments
Disease countNot applicable (varies for different studies)Clinician-rated disease counts derived from medical records or clinician diagnosis
Self-reported disease counts based on questionnaires or interviews
Not applicable (varies for different studies)Single diseases added to give a total number of diseases/conditions per individualNo weighting of diseases regarding severity or prognosis
Chronic Disease Score (CDS)/RxRisk Model1517Original CDS15: adult HMO enrollees from a single US HMO
Revised CDS16 derived and validated in 254,694 adult members of a US HMO.
RxRisk17 derived and validated in large samples of US HMO enrollees
Automated pharmacy data during a 1-year periodTo develop a stable measure of chronic disease status using routine pharmacy data rather than chart reviewOriginal CDS considered 17 disease states, weighted by an expert panel
Score based on history of dispensed drugs for 1 year, adjusted for age and sex
Subsequent versions used empirically derived weights and expanded number of diseases16,17
Limited number of disease states
Weighting of original CDS based on consensus rather than empirical data (addressed by subsequent versions)
Charlson Index18Derived in 559 US medical inpatients
Validated in 685 women receiving treatment for breast cancer
Various versions are available; 17 to 22 disease categories, including age
In different forms, can be administered by a health professional on paper or electronically or self-completed as a questionnaire
To predict 1-year mortality among patients admitted to hospital
Later adapted to predict costs19
Each disease is given a weighting of 1 to 6 and weighted scores are summated; this score can also be combined with age
Variations have been developed to use ICD-9 data, namely, Romano et al (Dartmouth- Manitoba score),20 Deyo et al,21 D’Hoore et al,22 Ghali et al,23 Rius et al24
Limited number of diseases
Prognoses vary between cancers yet have similar rating
Needs information about severity of some conditions
Prognosis for some conditions has improved since index developed
Adjusted Clinical Groups (ACG) System25Derived and validated in US using large HMO databases
Validation sample also included 30,000 Medicaid recipients
Age, sex, and diagnosis codes from medical records or insurance claims coded using the ICD or Read code systems
Data entered into ACG System software available at cost under license
Originally devised to predict morbidity burden and use of health care resources
System developed to provide a number of tools with different purposes
Collapsed into Initial Diagnosis Codes then to calculate ADGs (32); CADGs (12); MACs (26); ACGs (102). Each ACG includes individuals with a similar pattern of morbidity and similar expected resource useNeed to purchase bespoke software
Based on records or claims data so dependent on reliability of those data
Cumulative Index Illness Rating Scale (CIRS)26,27Hospitalized men in the United States26 and subsequently older adults in ambulatory settings27A rating scale consisting of 14 body systems categories that can be filled in by trained assessors directly during clinical consultation or from medical records.
Free access
To assess the medical burden of chronic illnessEach body system has a severity rating of 0 to 4, which are summated to create a total score (0–56), or presented as an index based on the number of categories scoring 2 or more.
Several variations exist
Requires training based on a manual. Broad body system groups
Prognoses vary among types of condition and may have improved since index was devised
(Duke Severity Illness Check-list (DUSOI) index2830Developed in 249 adult patients attending a family practice in the United StatesSeverity of illness checklist for measuring a person’s illness severity
Can be filled in during clinical consultation or from medical records
Available from author
To quantify the burden of illness as measured by the physicianEach diagnosis is rated on 4 levels: symptom, complication, prognosis without treatment, prognosis with treatment
Various severity scores are calculated using the ratings (from 0 to 4) for each parameter of every diagnosis
Subjective judgment is required on the part of the assessor
Requires training
  • ADGs=Adjusted Diagnosis Groups; CADGS = collapsed Aggregated Diagnosis Groups; HMO=health maintenance organization, ICD=International Classification of Diseases; MACs=major Adjusted Categories.