Table 1.

A comparison of major comorbidity indices.

IndexFeature	Charlson comorbidity indexa	Elixhauser comorbidity measurea	Functional comorbidity index	Multimorbidity index	Rheumatic disease comorbidity index
Number of diseasesb	19	30	18	40	11
Development year	1987	1998	2005	2015	2007
Original study population	Medical inpatients and breast cancer patients	Medical inpatients	General population and spine center patients	Rheumatoid arthritis patients	Rheumatoid arthritis, lupus, osteoarthritis, and fibromyalgia patients
Original outcome studied	One-year mortality	Length of stay, hospital costs, and hospital mortality	Physical function	Health-related quality of life	Mortality, hospitalization, disability, and costs
Administrative database use	Yes	Yes	Yes	Yes	Yes
Self-report use	Yes	No	No	No	Yes
Weightage versions	Weighted	Weighted and unweighted	Unweighted	Weighted and unweighted	Weighted
Fibromyalgia included	No	No	No	No	No

^aIncludes adaptations.

^bIncluding different severities of a single disease.