ICD-10-CM Coding Guidelines – Conventions

ICD 10 CM MECOpedia

ICD-10-CM Coding Guidelines – Conventions

ICD-10-CM (International Classification of Diseases, 10th Revision, Clinical Modification) – By CMS (Centers for Medicare and Medicaid Services) and NCHS (National Center for Health Statistics)

The ICD 10 CM is based on the ICD 10 published by the WHO (World Health Organization).

Conventions for the ICD-10-CM (General Rules)

  1. The Alphabetic Index and Tabular List

The ICD-10-CM is divided into the Alphabetic Index and the Tabular List,

The Alphabetic Index consists of the following parts:

  1.   The Index of Diseases and Injury
  2.   The Table of Neoplasm’s
  3.   The Table of Drugs and Chemicals
  4.   The Index of External Causes of Injury

Tabular List consist of a structured list of codes divided into chapters based on the body system or condition.

  1. Format and Structure

ICD 10 CM Codes maybe 3, 4, 5, 6 or 7 characters.

  1. Character 1 is alpha (Except “U” – Reserved for future expansion)
  2. Character 2 is numeric
  3. Character 3-7 are alpha or numeric
  4. Use a decimal after 3 characters.
  5. Placeholder

The “X” is used as a placeholder. Certain ICD 10 CM codes have applicable 7th character. If a code that requires a 7 character and is not having 6 characters, a placeholder “X” must be used to fill in the empty characters.

  1. Abbreviations

NEC “Not elsewhere classifiable” – When specific code is not available for a condition, then use other specified codes.

NOS “Not otherwise specified” – When the description itself not complete to select appropriate code, then use unspecified codes.

  1. Punctuation

[ ] Brackets are used

  • Alphabetic Index to identify manifestation codes.
  • Tabular List to enclose synonyms, alternative wording or explanatory phrases.

( ) Parentheses are used

Both Alphabetic Index and Tabular List to enclose supplementary words that may be present or absent in the statement of a disease.

: Colons are used

Tabular List after an incomplete term which needs one or more of the words following the colon to make it assignable to a given category.

6. Other and Unspecified codes

         “Other” codes

Codes titled “other” or “other specified” – When there is sufficient information in the medical record but a specific code does not exist. Then select “other specified” code.

          “Unspecified” codes

Codes titled “unspecified” – When the information in the medical record is insufficient to assign a more specific code. Then select the “unspecified” code.

  1. Includes Notes

This appears under a three-character code title to further define. List of terms is included under some codes. These terms are the conditions for which that code is to be used.

  1. Excludes Notes

                 Excludes 1: “Not coded here”- Is indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital and an acquired form of the same condition.

                 Excludes 2: “Not included here” – Is indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

  1. Etiology/manifestation convention(“code first”, “use additional code” and “in diseases classified elsewhere” notes)
    • Certain disease conditions have both an underlying etiology and multiple body system manifestations. For such cases, the underlying condition should be sequenced first followed by the manifestation.
    • Wherever such a combination exists, there is a “use additional code”note at the etiology code, and a “code first” note at the manifestation code. These indicate the proper sequencing order of the codes (etiology followed by manifestation).
    • In most cases the manifestation codes will have in the code title, “in diseases classified elsewhere.” are never permitted to be used as first-listed or principal diagnosis codes. They must be used in conjunction with an underlying condition.

Note: There are manifestation codes that do not have “in diseases classified elsewhere” in the title. For such codes, there is a “use additional code” note at the etiology code and a “code first” note at the manifestation code and the rules for sequencing apply.

  • Sometimes, In the Alphabetic Index, both conditions are listed together with the etiology code first followed by the manifestation codes in brackets. The code in brackets is always to be sequenced second.
  • “Code first” and “Use additional code” notes are also used as sequencing rules in the classification for certain codes that are not part of an etiology/ manifestation combination.
  1. “See” and “See Also”

                 The “see” instruction following a main term in the Alphabetic Index indicates that another term should be referenced to locate the correct code.

                   A “see also” instruction following a main term in the Alphabetic Index instructs that there is another main term that may also be referenced that may be useful. It is not necessary to follow the “see also” note when the original main term provides the necessary code.

  1. Default codes

A code listed next to a main term in the ICD-10-CM Alphabetic Index is referred to as a default code.

If a condition is documented in a medical record without any additional information, such as acute or chronic, the default code should be assigned.