Characteristics and Application of the Most Commonly Studied Multimorbidity Measures in Outpatient Settings
| Measure | Original Derivation/Validation Populations | Information Needed | Original Purpose of Score | How Information Is Used | Comments |
|---|---|---|---|---|---|
| Disease count | Not 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 individual | No weighting of diseases regarding severity or prognosis |
| Chronic Disease Score (CDS)/RxRisk Model15–17 | Original 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 period | To develop a stable measure of chronic disease status using routine pharmacy data rather than chart review | Original 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 Index18 | Derived 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 Free | 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) System25 | Derived 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 use | Need to purchase bespoke software Based on records or claims data so dependent on reliability of those data |
| Cumulative Index Illness Rating Scale (CIRS)26,27 | Hospitalized men in the United States26 and subsequently older adults in ambulatory settings27 | A 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 illness | Each 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) index28–30 | Developed in 249 adult patients attending a family practice in the United States | Severity 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 physician | Each 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.