Etiology/manifestation convention (“code first”, “use additional code” and “in diseases 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, if applicable, 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. 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. 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 with Parkinson’s disease. In the Alphabetic Index, a code from category G20 is listed first, followed by code F02.80 or F02.81- in brackets.

A code from category 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. See Section I.B.7. Multiple coding for a single condition. 14. “And” The word “and” should be interpreted to mean either “and” or “or” when it appears in a title.

For example, cases of “tuberculosis of bones”, “tuberculosis of joints” and “tuberculosis of bones and joints” are classified to subcategory A18.0, Tuberculosis of bones and joints. 15. “With” The word “with” or “in” should be interpreted to mean “associated with” or “due to” when it appears in a code title, the Alphabetic Index (either under a main term or subterm), or an instructional note in the Tabular List.

The classification presumes a causal relationship between the two conditions linked by these terms in the Alphabetic Index or Tabular List.

These conditions should be coded as related even in the absence of provider documentation explicitly linking them, unless the documentation clearly states the conditions are unrelated or when another guideline exists that specifically requires a documented linkage between two conditions (e.g., sepsis guideline for “acute organ dysfunction that is not clearly associated with the sepsis”).

For conditions not specifically linked by these relational terms in the classification or when a guideline requires that a linkage between two conditions be explicitly documented, provider documentation must link the conditions in order to code them as related.

The word “with” in the Alphabetic Index is sequenced immediately following the main term or subterm, not in alphabetical order. 16. “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. 17. “Code also” note A “code also” note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction. The sequencing depends on the circumstances of the encounter.