Abstract
The object of this article was to systematically review available methods to measure
comorbidity and to assess their validity and reliability. A search was made in Medline
and Embase, with the keywords comorbidity and multi-morbidity, to identify articles
in which a method to measure comorbidity was described. The references of these articles
were also checked, and using a standardized checklist the relevant data were extracted
from these articles. An assessment was made of the content, concurrent, predictive
and construct validity, and the reliability. Thirteen different methods to measure
comorbidity were identified: one disease count and 12 indexes. Data on content and
predictive validity were available for all measures, while data on construct validity
were available for nine methods, data on concurrent validity, and interrater reliability
for eight methods, and data on intrarater reliability for three methods. The Charlson
Index is the most extensively studied comorbidity index for predicting mortality.
The Cumulative Illness Rating Scale (CIRS) addresses all relevant body systems without
using specific diagnoses. The Index of Coexisting Disease (ICED) has a two-dimensional
structure, measuring disease severity and disability, which can be useful when mortality
and disability are the outcomes of interest. The Kaplan Index was specifically developed
for use in diabetes research. The Charlson Index, the CIRS, the ICED and the Kaplan
Index are valid and reliable methods to measure comorbidity that can be used in clinical
research. For the other indexes, insufficient data on the clinimetric properties are
available.
Keywords
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Article info
Publication history
Accepted:
August 27,
2002
Received in revised form:
July 19,
2002
Received:
February 15,
2001
Identification
Copyright
© 2003 Elsevier Science Inc. Published by Elsevier Inc. All rights reserved.
