# Charlson Comorbidities

    library(medicalcoder)
    packageVersion("medicalcoder")
    ## [1] '0.8.0'

# Introduction

The medicalcoder package implements several variants of the Charlson comorbidities algorithm.

- `charlson_deyo1992`: Deyo’s original set of codes (Deyo et al. 1992; Quan et al. 2005)
- `charlson_quan2005` and `charlson_quan2011`: Codes and index scoring (Quan et al. 2005, 2011)
- `charlson_cdmf2019`: (Glasheen et al. 2019)

# ICD Codes and Index Scores

End users can access the lookup tables for the mapping between ICD-9 and ICD-10 codes to conditions and the index scoring in `data.frame`s from the `get_charlson_codes()` and `get_charlson_index_scores()` calls respectively.

    str(get_charlson_codes())
    ## 'data.frame':    7410 obs. of  9 variables:
    ##  $ icdv             : int  9 9 9 9 9 9 9 9 9 9 ...
    ##  $ dx               : int  1 1 1 1 1 1 1 1 1 1 ...
    ##  $ full_code        : chr  "003.1" "007.2" "007.4" "010" ...
    ##  $ code             : chr  "0031" "0072" "0074" "010" ...
    ##  $ condition        : chr  "aids" "aids" "aids" "aids" ...
    ##  $ charlson_cdmf2019: int  1 1 1 1 1 1 1 1 1 1 ...
    ##  $ charlson_deyo1992: int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ charlson_quan2005: int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ charlson_quan2011: int  0 0 0 0 0 0 0 0 0 0 ...
    str(get_charlson_index_scores())
    ## 'data.frame':    21 obs. of  6 variables:
    ##  $ condition_description: chr  "AIDS" "AIDS/HIV" "HIV infection, no AIDS" "Any malignancy" ...
    ##  $ condition            : chr  "aids" "aidshiv" "hiv" "mal" ...
    ##  $ charlson_cdmf2019    : int  6 NA 3 2 1 1 1 1 2 1 ...
    ##  $ charlson_quan2011    : int  NA 4 NA 2 0 1 2 2 1 0 ...
    ##  $ charlson_quan2005    : int  NA 6 NA 2 1 1 1 1 2 1 ...
    ##  $ charlson_deyo1992    : int  NA 6 NA 2 1 1 1 1 2 1 ...

# Applying Charlson

Example: applying the Quan et al. (2005) variant of the Charlson comorbidities to the `mdcr` data can be done as follows.

    mdcr_results <-
      comorbidities(
        data = mdcr,
        id.vars = "patid",
        icdv.var = "icdv",
        icd.codes = "code",
        dx.var = "dx",
        flag.method = "current",
        poa = 1,
        primarydx = 0,
        method = "charlson_quan2005"
      )

The return object is a `data.frame` with 0/1 integer indicator columns for the relevant conditions, the id.vars (if applicable), `age_score` (if age, in years, is supplied), `num_cmrb` the number of comorbidities, `cmrb_flag` a 0/1 indicator for presence of at least one comorbidity, and `cci` the Charlson Comorbidity Index.

    str(mdcr_results)
    ## Classes 'medicalcoder_comorbidities' and 'data.frame':   38262 obs. of  22 variables:
    ##  $ patid    : int  10000 10002 10005 10006 10008 10010 10014 10015 10017 10018 ...
    ##  $ aidshiv  : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ mal      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ cebvd    : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ copd     : int  1 0 0 0 0 0 0 0 0 0 ...
    ##  $ chf      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ dem      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ dmc      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ dm       : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ hp       : int  0 0 0 0 0 0 0 1 0 0 ...
    ##  $ mld      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ msld     : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ mst      : int  0 0 1 0 0 0 0 0 0 0 ...
    ##  $ mi       : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ pud      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ pvd      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ rnd      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ rhd      : int  0 0 0 0 0 0 0 0 0 0 ...
    ##  $ num_cmrb : int  1 0 1 0 0 0 0 1 0 0 ...
    ##  $ cmrb_flag: int  1 0 1 0 0 0 0 1 0 0 ...
    ##  $ cci      : int  1 0 6 0 0 0 0 2 0 0 ...
    ##  $ age_score: int  NA NA NA NA NA NA NA NA NA NA ...
    ##  - attr(*, "method")= chr "charlson_quan2005"
    ##  - attr(*, "id.vars")= chr "patid"
    ##  - attr(*, "flag.method")= chr "current"

Call `summary()` on the return object for a list of summary objects. These can be used to generate output tables to the end user’s liking.

    str(summary(mdcr_results))
    ## List of 3
    ##  $ conditions   :'data.frame':   22 obs. of  4 variables:
    ##   ..$ condition_description: chr [1:22] "AIDS/HIV" "Any malignancy" "Cerebrovascular disease" "Chronic pulmonary disease" ...
    ##   ..$ condition            : chr [1:22] "aidshiv" "mal" "cebvd" "copd" ...
    ##   ..$ count                : num [1:22] 7 2301 411 3415 684 ...
    ##   ..$ percent              : num [1:22] 0.0183 6.0138 1.0742 8.9253 1.7877 ...
    ##  $ age_summary  :'data.frame':   1 obs. of  3 variables:
    ##   ..$ age_score: chr NA
    ##   ..$ count    : int 38262
    ##   ..$ percent  : num 100
    ##  $ index_summary:'data.frame':   1 obs. of  5 variables:
    ##   ..$ min   : int 0
    ##   ..$ q1    : num 0
    ##   ..$ median: num 0
    ##   ..$ q3    : num 1
    ##   ..$ max   : int 12

Counts and percentages of patients in the mdcr example data sets with the Quan et al. (2005) comorbidities.
| Count | Percentage
--- | --- | ---
Comorbidity
AIDS/HIV | 7 | 0.018
Any malignancy | 2301 | 6.014
Cerebrovascular disease | 411 | 1.074
Chronic pulmonary disease | 3415 | 8.925
Congestive heart failure | 684 | 1.788
Dementia | 13 | 0.034
Diabetes with chronic complications | 13 | 0.034
Diabetes without chronic complications | 441 | 1.153
Hemiplegia or paraplegia | 1177 | 3.076
Liver disease, mild | 562 | 1.469
Liver disease, moderate to severe | 206 | 0.538
Metastatic solid tumor | 453 | 1.184
Myocardial infarction | 10 | 0.026
Peptic ulcer disease | 45 | 0.118
Peripheral vascular disease | 217 | 0.567
Renal disease | 877 | 2.292
Rheumatic disease | 136 | 0.355
Total Comorbidities
>= 1 | 9789 | 25.584
>= 2 | 1075 | 2.810
>= 3 | 94 | 0.246
>= 4 | 9 | 0.024
>= 5 | 1 | 0.003

# References

Deyo, Richard A, Daniel C Cherkin, and Marcia A Ciol. 1992. “Adapting a Clinical Comorbidity Index for Use with ICD-9-CM Administrative Databases.” Journal of Clinical Epidemiology 45 (6): 613–19. https://doi.org/https://doi.org/10.1016/0895-4356(92)90133-8.
Glasheen, William P, Tristan Cordier, Rajiv Gumpina, Gil Haugh, Jared Davis, and Andrew Renda. 2019. “Charlson Comorbidity Index: ICD-9 Update and ICD-10 Translation.” American Health & Drug Benefits 12 (4): 188. https://pubmed.ncbi.nlm.nih.gov/31428236/.
Quan, Hude, Bo Li, Colette M. Couris, et al. 2011. “Updating and Validating the Charlson Comorbidity Index and Score for Risk Adjustment in Hospital Discharge Abstracts Using Data from 6 Countries.” American Journal of Epidemiology 173 (6): 676–82. https://doi.org/10.1093/aje/kwq433.
Quan, Hude, Vijaya Sundararajan, Patricia Halfon, et al. 2005. “Coding Algorithms for Defining Comorbidities in ICD-9-CM and ICD-10 Administrative Data.” Medical Care 43 (11): 1130–39. https://doi.org/10.1097/01.mlr.0000182534.19832.83.