Calculate comorbidities, Charlson and van Walraven scores, perform fast and accurate validation, conversion, manipulation, filtering and comparison of ICD-9 and ICD-10 codes. This package enables a work flow from raw lists of ICD codes in hospital databases to comorbidities. ICD-9 and ICD-10 comorbidity mappings from Quan (Deyo and Elixhauser versions), Elixhauser and AHRQ included. Common ambiguities and code formats are handled.
icd is used by many researchers around the world who work in public health, epidemiology, clinical research, nutrition, journalism, health administration and more. I’m grateful for contact from people in these fields for their feedback and code contributions, and I’m pleased to say that
icd has been used in works like the Pulitzer finalist work on maternal death by ProPublica.
See also the vignettes and examples embedded in the help for each function for more. Here’s a taste:
# install.packages("icd") library(icd) # Typical diagnostic code data, with many-to-many relationship patient_data #> visit_id icd9 #> 1 1000 40201 #> 2 1000 2258 #> 3 1000 7208 #> 4 1000 25001 #> 5 1001 34400 #> 6 1001 4011 #> 7 1002 4011 #> 8 1000 <NA> # get comorbidities using Quan's application of Deyo's Charlson comorbidity groups comorbid_charlson(patient_data) #> MI CHF PVD Stroke Dementia Pulmonary Rheumatic PUD LiverMild #> 1000 FALSE TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE #> 1001 FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE #> 1002 FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE #> DM DMcx Paralysis Renal Cancer LiverSevere Mets HIV #> 1000 TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE #> 1001 FALSE FALSE TRUE FALSE FALSE FALSE FALSE FALSE #> 1002 FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE # or go straight to the Charlson scores: charlson(patient_data) #> 1000 1001 1002 #> 2 2 0
Look at the help files for details and examples of almost every function in this package. There are several vignettes showing the main features:
Many users have emailed me directly for help, and I’ll do what I can, but it is often better to examine or add to the list of issues so we can help each other. Advanced users may look at the source code, particularly the extensive test suite which exercises all the key functions.
ICD-9 codes are still in heavy use around the world, particularly in the USA where the ICD-9-CM (Clinical Modification) was in widespread use until the end of 2015. ICD-10 has been used worldwide for reporting cause of death for more than a decade, and ICD-11 is due to be released in 2018. ICD-10-CM is now the primary coding scheme for US hospital admission and discharge diagnoses used for regulatory purposes and billing. A vast amount of electronic patient data is recorded with ICD-9 codes of some kind: this package enables their use in R alongside ICD-10.
A common requirement for medical research involving patients is determining new or existing comorbidities. This is often reported in Table 1 of research papers to demonstrate the similarity or differences of groups of patients. This package is focussed on fast and accurate generation of this comorbidity information from raw lists of ICD-9 codes.
ICD-9 codes are not numbers, and great care is needed when matching individual codes and ranges of codes. It is easy to make mistakes, hence the need for this package. ICD-9 codes can be presented in short 5 character format, or decimal format, with a decimal place separating the code into two groups. There are also codes beginning with V and E which have different validation rules. Zeroes after a decimal place are meaningful, so numeric ICD-9 codes cannot be used in most cases. In addition, most clinical databases contain invalid codes, and even decimal and non-decimal format codes in different places. This package primarily deals with ICD-9-CM (Clinical Modification) codes, but should be applicable or easily extendible to the original WHO ICD-9 system.
ICD-10 has a somewhat simpler format, with consistent use of a letter, then two alphanumeric characters. However, especially for ICD-10-CM, there are a multitude of qualifiers, e.g. specifying recurrence, laterality, which vastly increase the number of possible codes. This package recognizes validity of codes by syntax alone, or whether the codes appear in a canonical list. The current ICD-10-CM master list is the 2016 set. There is no capability of converting between ICD-9 and ICD-10, but comorbidities can be generated from older ICD-9 codes and newer ICD-10 codes in parallel, and the comorbidities can then be compared.