The conventions for the ICD-10-CM are the general rules for use of the classification independent of the guidelines. These conventions are incorporated within the Alphabetic Index and Tabular List of the ICD-10-CM as instructional notes.
1. Abbreviations
a) NEC “Not elsewhere classifiable”: This abbreviation in the Alphabetic Index represents “other specified”. When a specific code is not available for a condition, the Alphabetic Index directs the coder to the “other specified” code in the Tabular List.
b) NOS “Not otherwise specified”: NOS “Not otherwise specified”
2. Punctuation
a) [ ] Brackets are used in the Tabular List to enclose synonyms, alternative wording or explanatory phrases. Brackets are used in the Alphabetic Index to identify manifestation codes.
b) ( ) Parentheses are used in both the Alphabetic Index and Tabular List to enclose supplementary words that may be present or absent in the statement of a disease or procedure without affecting the code number to which it is assigned. The terms within the parentheses are referred to as nonessential modifiers.
c) : Colons are used in the Tabular List after an incomplete term which needs one or more of the modifiers following the colon to make it assignable to a given category.
3. Use of “and:
When the term “and” is used in a narrative statement it represents and/or.
4. Inclusion Notes
List of terms is included under some codes. These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of “other specified” codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
5. Exclude Notes
a) Exclude1: It means “NOT CODED HERE!” An Excludes1 note 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 form versus an acquired form of the same condition.
b) Exclude 2: A type 2 excludes note represents “Not included here”. An excludes2 note 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 Excludes 2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
6. Etiology/manifestation convention (“code first”, “use additional code” and “in disease classified elsewhere” notes)
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition 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 instructional notes 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.” Codes with this title are a component of the etiology/ manifestation convention. The code title indicates that it is a manifestation code. “In diseases classified elsewhere” codes are never permitted to be used as first-listed or principal diagnosis codes. They must be used in conjunction with an underlying condition code and they must be listed following the underlying condition.
See category F02, Dementia in other diseases classified elsewhere, for an example of this convention.
See category F02, Dementia in other diseases classified elsewhere, for an example of this convention.
There are manifestation codes that do not have “in diseases classified elsewhere” in the title. For such codes a “use additional code” note will still be present and the rules for sequencing apply.
In addition to the notes in the Tabular List, these conditions also have a specific Alphabetic Index entry structure. 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.
An example of the etiology/manifestation convention is dementia in Parkinson’s disease. In the Alphabetic Index, code G20 is listed first, followed by code F02.80 or F02.81 in brackets. Code G20 represents the underlying etiology, Parkinson’s disease, and must be sequenced first, whereas codes F02.80 and F02.81 represent the manifestation of dementia in diseases classified elsewhere, with or without behavioral disturbance.
“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.
7. “And”
The word “and” should be interpreted to mean either “and” or “or” when it appears in a title.
8. “With”
The word “with” should be interpreted to mean “associated with” or “due to” when it appears in a code title, the Alphabetic Index, or an instructional note in the Tabular List.
The word “with” in the Alphabetic Index is sequenced immediately following the main term, not in alphabetical order.
9. “See” and “See Also”
The “see” instruction following a main term in the Alphabetic Index indicates that another term should be referenced. It is necessary to go to the main term referenced with the “see” note 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 provide additional Alphabetic Index entries that may be useful. It is not necessary to follow the “see also” note when the original main term provides the necessary code.
Important Resources about ICD-10 Transition:
The ICD-10 Transition Introduction
Important Resources about ICD-10 Transition:
The ICD-10 Transition Introduction
