Question

I cannot find a definitive guide to icd9 code formats.

Can anyone explain the format – especially the use of trailing and leading zeros?

A C# regex for icd9 and icd10 codes would also be nice.

Thanks!

Answer 1

I was looking for the same thing and found what I believe to be a more complete answer. Thought I’d help anyone else coming in the future.

ICD-9 Regex

The ICD 9 format has a bunch of ways it can be formatted. It can begin with V, E, or a number.

• If it begins with V, then it has 2 numbers, a decimal, then up to
  two numbers
  • Examples: V10.12 and V12
• If it begins when E, then it has 3 numbers, the decimal place, then up to two numbers
  • Examples: E000.0 and E002
• If it begins with a number, then it is up to 3 numbers, a decimal, then up to two numbers
  • Examples: 730.12 and 730

A good regex that checks all these rules is (Credit goes to sascomunitt)

^(V\d{2}(\.\d{1,2})?|\d{3}(\.\d{1,2})?|E\d{3}(\.\d)?)$

ICD-10 Regex

According to http://www.cms.gov ICD-10 has the following rules:

• 3-7 Characters
• Character 1 is alpha (cannot be U)
• Character 2 is numeric
• Characters 3-7 are alphanumeric
• After 3 characters you use a decimal
• Use of dummy placeholder “x” (This is the only one I am not accounting for in my regex…)
• Alpha characters are not case sensitive

Here is the regex I came up with:

^[A-TV-Z][0-9][A-Z0-9](\.[A-Z0-9]{1,4})?$

Note These regexes are for javascript and may need tweaked for C# (I’m too lazy to test it right now)