Since 2010, Health IT in the US has worked on transitioning to ICD-10. The deadline to convert was moved back once to October 1, 2014, but this doesn’t happen when everyone is ready. Here’s a very brief introduction for those of you supporting health care organizations. Let’s consider a small physician practice for high-level clarity. I intend this series to give you a flavor for the kinds of questions many ask.
ICD-10 is a code set for specifying medical diagnoses and inpatient hospital procedures. If you’re identifying an outpatient procedure, that’s a separate thing: a CPT code. ICD stands for “International Statistical Classification of Diseases and Related Health Problems.” ICD-10 is the tenth revision, published by the World Health Organization. Work on ICD-10 started in 1983 and finished in 1992. As you’d guess, ICD-10 replaces ICD-9, the prior set still in use. You’ll find ICD-9 on electronic health records (EHR), on electronic claims from providers to payers, in research reports, in disease tracking, and on and on. ICD-10 will be used in all of those places and more.
ICD-10 codes are structured as strings up to 7 characters long, consisting of:
|5||Body part affected|
|6||Severity of illness|
|7||Extension placeholder (specificity)|
At a high level codes are grouped into chapters of one or two letters in the first character. As an example, codes “F00” to “F99” make chapter 5 about “Mental and behavioral disorders.” “Obsessive-compulsive disorder” is ICD-10 code “F42”, and “F42.0” narrows this to “Predominantly obsessional thoughts or ruminations.”
In fact, ICD-10 allows you to consider these axes when identifying a code:
- Manifestation or complication
- Specificity of anatomical site
- Chronicity (i.e. acute, subacute, chronic, unspecified vs. acute/subacute, chronic, unspecified, etc.)
- Degree (i.e., mild, moderate, severe, unspecified vs total/complete, partial/incomplete, etc.)
- Type (i.e., primary, secondary, unspecified, etc.)
- Laterality (i.e., R/L/unspecified or R/L/bilateral/unspecified)
- Episode of care (3-16 “extension” options, depending on code category)
- Trimester (i.e., 1, 2, 3,unspecified, etc.)
- Number of fetus (i.e. 1-5, other.)
Taken all the way, code “S72.044A” describes a “Nondisplaced fracture of base of the neck of right femur, initial encounter.” Whoa! As a researcher, imagine what you could learn from data on those fractures gathered from every hospital and clinic in the US. ICD-10 codes help normalize that data.
But normalization has its limits. Providers often employ formally trained coders to properly transcribe a physician’s diagnosis and procedures onto EHR records and claims. Through the looking glass, payers accept claims with codes at the detail level and adjudicate the claims using the codes to lookup reimbursement rules. Health networks might define disease populations by ICD-10 codes to help manage them, and policy makers write codes into laws and protocols. Similarly, researchers characterize disease populations by gathering clinical and claims data grouped by ICD-10 codes. Each group uses ICD-10 codes for its own purposes. Providers might record your care in one code and submit another code to your insurer to maximize reimbursement. It’s not easy to match up clinical and claims data.
In the US, ICD-10 is delivered in two taxonomies: ICD-10-CM for diagnoses, and ICD10-PCS covering inpatient hospital procedures.
ICD-10 has been translated into 42 languages. It’s the same code set across all; the descriptions get localized.
Looking for a sense of how much stuff is in ICD-10? While both ICD-9 and -10 get revised over time, at the end of 2012 there were 14,567 valid ICD-9-CM codes and 79,503 draft ICD-10-CM codes. The order of magnitude difference reflects the greater number of codes supported by the ICD-10 structure, increased specificity, and a better match to modern medical practice. The quantity of codes is distributed unevenly across chapters too. For example, chapter 19 on “Injury, Poisoning and Certain Other Consequences of External Causes” has the most codes, and went from 2,587 codes under ICD-9 to 42,970 under ICD-10. The chapter with the fewest codes is chapter 1, “Certain Infectious and Parasitic Diseases”, which went from 1,270 to 1,292 codes. As you would guess, every single chapter has more codes under ICD-10.