ICD-10 Coding Structure

With the introduction of ICD-10 as the new standard for diagnosis, information systems currently used in Canada, to collect and store ICD-9 and/or ICD-9-CM diagnostic codes, will need to be modified to accommodate the new coding structure for ICD-10.

Management information systems and software vendors should contact the appropriate federal/provincial/territorial representative from the National ICD-10/CCI Implementation Advisory Committee for implementation plans specific to each jurisdiction.

Code Structure

• ICD-10-CA has an Alpha-numeric format with a code size ranging from 3 to 6 characters as illustrated below:

Where C = alpha character
# = numeric character
N = numeric character or blank

• Future enhancements to ICD-10-CA may extend the code length to 7 alphanumeric characters.

    Other code structure implications are presented below.

    • Valid ICD-10-CA disease codes include three, four, five and six character codes. e.g.

    N72 Inflammatory disease of cervix uteri
    J20.6 Acute bronchitis due to rhinovirus
    M08.00 Juvenile Rheumatoid Arthritis (multiple sites)

    • The alphabetical character ‘U’ has been reserved for future use by WHO, but is a valid character.

    • The external cause "place of occurrence" is now indicated by a fourth character in ICD-10-CA. In ICD-9-CM it is a separate code, in ICD-9 for morbidity coding it is a 5th digit that is added to the E-code and in ICD-9 for mortality coding it is a separate code.

    • All injury codes (range S00-T98) must be coded in conjunction with an external cause code (range V01-Y98).

      Presentation Format

      The presentation format for an ICD-10-CA code includes a decimal after the third character in valid four, five and six character codes. Valid three character codes do not include the decimal place. Where the fourth, fifth and sixth character is not utilized there will be no character filling.

      With the introduction of alpha characters, it may be difficult to distinguish between the alpha O and the numeric 0 or the alpha I or the numeric 1. Systems should utilize a font that will visually distinguish these characters.

      Data Storage and Transmission

      The decimal after the third character should not be included in machine-readable data. CIHI will receive each ICD-10-CA code as a 6 character alphanumeric field. Where the fourth, fifth or sixth character is not utilized there will be no character filling. These positions should contain blanks.

      Morphology Codes

      Morphology disease codes may be used with neoplasm site codes. The code structure is different from the basic ICD-10-CA format; Morphology codes are 6-character alphanumeric, with a forward slash (/) after the fifth character. However, the first alpha character is not included in the machine readable code, therefore; the code structure is a 5-character numeric. The alpha M and the slash may be used for presentation purposes, but should not be included in the machine-readable representation of the code. Information Systems must allow for the collection of morphology codes and their appropriate site codes.

      Sizing Implications

      • The range of ICD-10-CA codes is A00.00 to Z99.99

      • The Morphology code range is M0000/0 to M9999/9

      • The number of codes increases to >30,000 in ICD-10-CA and CCI from just under 7000 in ICD-9/CCP and approximately 12,000 in ICD-9-CM.

      • There are 23 Chapters in ICD-10-CA vs 17 plus E Codes and V Codes in ICD-9/9-CM.

      • Maximum descriptor field size is 250.

        Other Issues

        • All asterisk (*) codes must be accompanied and preceded by at least one dagger (†) code. The asterisk and dagger symbols are not required to be collected by the system.

        • All injury codes (range S00-T98) must be coded in conjunction with an external cause code (range V01-Y98).

        • The WHO intends to protect the copyright for ICD-10. Software suppliers in Canada should contact CIHI regarding ICD-10 sub-licence inquiries.