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CCS Prep

Official ICD-9-CM Coding Conventions

A Must for CCS and CCS-P Certification Candidates

When coding on a day-to-day basis, most coding professionals don't think much about the underlying official ICD-9-CM coding conventions and how they fit into the classification system. But thoroughly understanding and using the conventions appropriately are essential to correct coding and questions involving the conventions may be found on the certification exams. Therefore, a review of each type of convention is helpful when studying for an exam or just to brush up on the meanings behind the symbols, notes and other conventions. In addition, many coders today use a computerized encoding system, and while these are useful tools and can help tremendously from an efficiency standpoint, some coders may need to review the underlying classification and conventions of ICD-9-CM that are not typically found in many encoding programs.


The two most commonly found abbreviations in ICD-9-CM are NEC and NOS. Many coders confuse these seemingly similar, but very different abbreviations.

NEC: Not Elsewhere Classified - This designation is used to indicate there is no separate specific code available to represent the condition documented. In this case, the diagnostic statement is specific, but the coding system is not specific enough.

NOS: Not Otherwise Specified - This designation is equivalent to the word "unspecified" and indicates that the documentation does not provide enough information to assign a more specific code.

Instructional Notes

There are several different types of instructional notes that appear throughout ICD-9-CM and provide important information to the coder. These include:

General Notes: May be found in both the alphabetic index and the tabular list; typically provide information related to a specific section or subsection. For example, in the fractures section of the tabular list, the following note appears:

Note: A fracture not indicated as closed or open should be classified as closed.

Inclusion and Exclusion Notes: These designations help the coder determine whether a particular category is included in the section or code category (inclusion note), or should be coded elsewhere and is not included (exclusion note). Coders must carefully note the location of the inclusion and exclusion notes to determine which code or range of codes they are applicable to. Example:

351 Facial nerve disorders

            Includes: disorders of 7th cranial nerve

            Excludes: that in newborn (767.5)

The includes and excludes notes above apply to all codes within category 351. Documentation indicating a disorder related to the 7th cranial nerve should be classified to this category. Conversely, if a facial nerve disorder is found on a newborn record, it would be classified to code 767.5, not to category 351. Be aware that excludes notes are always in an italicized font. Inclusion terms may be synonyms or conditions that are considered similar enough that they are classified together, but the terms are not exhaustive. Excludes notes may indicate mutually exclusive conditions (the diagnosis may be one condition or the other, but not both) or conditions that are included in other codes or categories elsewhere. There are many excludes notes that reference codes in the maternity and newborn chapters, because these conditions are classified differently than those found in the general population.

Use Additional Code: This designation is used to signal the coder that another additional code may be necessary to fully define the disease process or condition. If the condition that is indicated in the note is present in the documentation, it should always be assigned. A common example involves the assignment of an additional code to specify an infectious organism:

599.0 Urinary tract infection, site not specified

Use additional code to identify organism, such as Escherichia coli [E.coli] (041.4)

Code First Underlying Condition: This designation most commonly represents what is known as the "Manifestation/Etiology" sequencing rule. When a particular condition is due to another underlying causal condition, the underlying condition (etiology) code is sequenced first, followed by the code for the manifestation. In the alphabetic index, the underlying code is listed first, followed by the manifestation code, which is in brackets. A manifestation code can never be sequenced as the first-listed or principal diagnosis. Example:

456.2 Esophageal varices in diseases classified elsewhere

          Code first underlying cause, as:

                  cirrhosis of liver (571.0-571.9)

                  portal hypertension (572.3)

Code, If Applicable, Any Causal Condition First: A code with this note indicates this code may be assigned as a first-listed or principal diagnosis when the causal condition is unknown or not applicable. If the causal condition is known, then the code for that condition should be sequenced as the principal or first-listed diagnosis. Example:

590.0 Chronic pyelonephritis

          Code, if applicable, any causal condition first

Cross-Reference Index Notes

Cross references are included in the alphabetic index to instruct the coder to look elsewhere before assigning a final code.

Omit Code: This designation is used when no code is to be assigned at all. Example:


            cervix - omit code

See Condition: This note instructs the coder to refer to a main term for the condition. It is primarily found following index terms that are nouns for anatomical sites or adjectival forms of a disease term. Coders should instead search the index using a condition term. Examples:

      Cervix - see condition

      Diffuse - see condition

See and See Category: These designations refer the coder to another indexed entry. It is a mandatory instruction; the "See Category" instruction includes the category to which the coder is being redirected. Examples:

      Hookworm (anemia) (disease) (infestation) -

          see Ancylostomiasis

      Late effect

          encephalitis or encephalomyelitis (conditions classifiable to 323) -

                      see category 326

See Also: This designation indicates there is an additional indexed entry where the coder may find pertinent information related to the documented condition. It isn't necessary to refer to the additional entry if the information presented under the initial indexed entry contains all that is necessary for specific code assignment. Example:

      Leukoencephalopathy - see also Encephalitis 323.9


Several different types of punctuation marks appear in both the alphabetic index and the tabular list and each has a specific meaning.

Parentheses ( ):  These are used to enclose supplementary words (also known as non-essential modifiers) that may be present in the documentation without affecting the code assignment. Example:

198.4 Other parts of nervous system

          Meninges (cerebral) (spinal)

Brackets [ ]:  Brackets enclose synonyms, alternative terminology or explanatory phrases. Example:

482.2 Pneumonia due to Hemophilus influenzae [H. influenzae]

Alternatively, brackets may also appear beneath a code to indicate the fifth digits that are considered valid fifth digits for that code. This convention is applied for those instances where not all common fifth digits are considered valid for each subcategory within a category. Example:

715.0 Osteoarthrosis, generalized


The notation above indicates that only fifth digits of 0, 4 and 9 are valid for subcategory 715.0.

Slanted Brackets [ ]:  This type of bracket is used in the alphabetical index to indicate mandatory multiple coding. Both codes must be assigned to fully describe the condition and are sequenced in the order listed. Example:


           ventricular (paroxysmal)

                  psychogenic 316 [427.1]

Colon : Colons are used in the tabular list after an incomplete term that needs one or more of the modifiers that follow in order to make it assignable to a given category. Example:

443.0 Raynaud's syndrome



                phenomenon (secondary)

Braces }:  Braces enclose a series of terms, each of which is modified by the statement appearing to the right of the brace. Example:

560.2 Volvulus


          Strangulation }   of intestine, bowel, or colon




Other Conventions

Boldface Font: Boldface type is used for all codes and titles in the tabular list.

Italicized Font: Italicized type is used for all exclusion notes and to identify codes that should not be used to describe the first-listed or principal diagnosis.

Each of the above conventions is considered an integral part of the classification system and coders must ensure their complete understanding of the use of each one. Test your knowledge with the quiz below:


1.  The abbreviation NEC means:

      a. That the condition should be classified under another category

      b. The same thing as the NOS abbreviation

      c. That the condition documented has no specific code available for assignment.

      d. That multiple different conditions indexed may be classified here

2. If a code is enclosed in slanted brackets, it means:

      a. That the code should be sequenced as the first-listed or principal diagnosis

      b. That the code is considered a manifestation

      c. That the code should never be sequenced as first-listed or principal diagnosis

      d. Both b and c above

3. If a condition is included in an Excludes note, it means:

      a. That it is a mutually exclusive condition to the code under which it appears

      b. That the condition is a synonym for the code under which it appears

      c. That it may be considered an integral component of another code

      d. Both a and c above

This month's column has been prepared by Cheryl D'Amato, RHIT, CCS, director of HIM, facility solutions, and Melinda Stegman, MBA, CCS, clinical technical editor, Ingenix.

CPT is a registered trademark of the American Medical Association.



1. c. NEC means that the documentation includes a specific condition for which there is no code available.

2. d. A code found in a slanted bracket is considered a manifestation and should never be assigned as a first-listed or principal diagnosis.

3. d. An Excludes note term may be mutually exclusive or considered integral to another code. It would never be considered a synonym entry.

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