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 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.
See Section I.B.7. Multiple coding for a single condition
