Table 1.
The 4 multi-morbidity scores included in the comparison study.
| Abbreviation Full score name | Number of conditions* | Description |
|---|---|---|
| DHHS US Department of Health and Human Services |
20 | The 20 conditions were selected by the DHHS because they are chronic, prevalent, and “potentially amenable to public health or clinical interventions or both.”10,15 However, we modified the set of ICD codes used to define cancer by excluding non-melanoma skin cancer. This is the multimorbidity score that we use in our previous normative study,10 and in several previous publications on multi-morbidity in the REP.2,5,6,9 |
| CCS Clinical Classifications Software chronic conditions |
190 | We constructed a multi-morbidity score based on the Clinical Classifications Software (CCS) enumeration of medical conditions.16-17 The CCS groups each of the 15,072 billable ICD-9 diagnosis codes into one of 283 categories (i.e., conditions). From among all ICD-9 diagnosis codes, we identified 4,584 codes flagged as “chronic” via the Chronic Condition Indicator (CCI) tool.18 We used the subset of chronic codes to identify the 190 chronic condition categories included in our multi-morbidity score. The 93 CCS categories with no diagnosis codes flagged as “chronic” were not included in the calculation of the CCS score. |
| CHAP Chapters of the CCS chronic conditions |
18 | We constructed a condensed version of the CCS multi-morbidity score by using only the 18 broad chapters into which all CCS categories are grouped. To define the chapters multi-morbidity score, the list of 4,584 ICD-9 diagnosis codes flagged as chronic were used from the CCS score.16-18 The 18 CCS chapters roughly correspond to the body’s key organ systems. |
| ELIX Elixhauser Comorbidity Index |
31 | We used the list of 31 conditions and the coding as described by Quan, et al. to define the Elixhauser Comorbidity Index.19-22 The Elixhauser Comorbidity Index is one of the most commonly used and most studied measures of comorbidity.19-22 |
DHHS = Department of Health and Human Services, 20 condition score; ICD = International Classification of Diseases; REP = Rochester Epidemiology Project; CCS = Clinical Classifications Software, 190 chronic condition score; CHAP = Body system chapters (collapsed CCS system), 18 chapters score; ELIX = Elixhauser Comorbidity Index, 31 condition score.
Many conditions are similar across the 4 different scores; however, the level of granularity differs among the scores. For example, hypertension is included in the DHHS list as one condition, whereas ELIX splits hypertension into two conditions (uncomplicated and complicated hypertension). The same is true for how ELIX splits diabetes into complicated and uncomplicated variants. The level of granularity varies greatly for cancer: the CCS score includes 33 separate types of cancer; the DHHS and CHAP scores group together all types of cancer into one category; the ELIX score includes 3 separate types of cancer for lymphoma, metastatic cancer, and solid tumors without metastasis. For more details, see Supplemental Digital Content 1.