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Principles of Pediatric ICD-10-CM Coding
By Jeffrey F. Linzer
American Academy of PediatricsCopyright © 2013 American Academy of Pediatrics
All rights reserved.
Guidelines and Conventions of ICD-10 Coding
Like its predecessor, International Classification of Diseases, Ninth Revision, Clinical Modification, ICD-10-CM has 3 main steps for selection of an accurate code
1. Look up a diagnosis or condition in the alphabetic index first and then in the tabular list.
2. Read all instructional notes in both the alphabetic index and the tabular list.
3. When in the tabular list, be sure to check for instructions at the 3-digit category level in addition to the code level.
Beyond these 3 steps are the official guidelines and conventions of ICD-10-CM as established by the Centers for Medicare & Medicaid Services (CMS) and the National Center for Health Statistics (NCHS) and approved by the cooperating parties for ICD-10-CM: the American Hospital Association, the American Health Information Management Association, CMS, and NCHS. The guidelines provide additional instruction beyond the conventions (general rules) contained directly within the alphabetic index and tabular list of the code set. Use of the official guidelines of ICD-10-CM is required under the Health Insurance Portability and Accountability Act when using the code set. However, conventions take precedence over the guidelines.
In this chapter, we will look at the structure of ICD-10-CM codes and review of some key guidelines and conventions that apply to the overall code set. Chapter- and diagnosis-specific guidelines of ICD-10-CM will be included later in reviews of each associated chapter.
First, let's note a few key definitions associated with the general conventions and guidelines of ICD-10-CM.
Character — a letter or number that serves as the building block of ICD-10-CM codes, sometimes referred to as digits
Category — a 3-character unit that may be a complete code when no further subcategories exist but often serves as the base for building a 4- to 7-character code, categories are the main entries of the tabular list
Subcategory — a further defined category of 4 to 6 characters that is not a complete code
Code — a complete set of characters for which there are no further subdivisions, 3 to 7 characters long, describing a condition or reason for an encounter or related factors such as external causes
And — means "and/or" in ICD-10-CM
With — means "with" or "due to" in ICD-10-CM
Principal diagnosis — in a non-outpatient setting, that condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital or other non-outpatient setting for care (including home health agencies)
First-listed diagnosis — in an outpatient facility or office setting, the diagnosis, condition, problem, or other reason for encounter/visit shown in the medical record to be chiefly responsible for the services provided
Combination code — a single code that represents either multiple conditions or a single condition and an associated secondary process or complication
Placeholder — ICD-10-CM uses the letter "X" as a placeholder. Where a subcategory of less than 6 characters requires 7 characters for a complete code, an "X" must be used as a placeholder filling in any undefined characters.
Sequela — a late effect of an illness or injury that is no longer in the acute phase
These terms are used throughout the ICD-10-CM code set and the guidelines for its use.
As shown by the definition above, codes in ICD-10-CM are alphanumeric and may be from 3 to 7 characters long. All alphabetic characters except the letter U are used. The pattern of the code structure is 3 characters before a decimal followed by up to 4 more characters.
The first 3 characters form the code category. The first character is an alphabetic. The second character is numeric. Remaining characters may be alphabetic or numeric. Alphabetic characters are not case sensitive. The code category may then be further expanded on with etiology, severity, site, manifestations, or intent within the fourth through sixth characters. The seventh character is an extension required in some categories to further define the episode of care, status of fracture healing, the number of the fetus in obstetrical conditions, or the site of recording of the Glasgow coma scale.
Examples of complete codes
R05 Cough R06.2 Wheezing
G43.C0 Periodic headache syndromes in child or adult, not intractable
G40.B01 Juvenile myoclonic epilepsy, not intractable, with status epilepticus
S52.311D Greenstick fracture of shaft of radius, right arm, subsequent encounter for fracture with routine healing
T37.5X5A Adverse effect of antiviral drugs, initial encounter
The letter "X" is used as a placeholder embedded in some codes to either provide for future expansion of a code category or where a seventh character is required but a code is less than 6 characters long, the placeholder must be added to fill the those spaces between the end of the code and the seventh character.
H60.8X1 Other otitis externa, right ear
H60.8X2 Other otitis externa, left ear
M48.52XA Collapsed vertebra, not elsewhere classified, cervical region, initial encounter
X32.XXXA Exposure to sunlight, first encounter
The codes H60.8X1 and H60.8X2 are examples of the placeholder used to maintain the sixth character structure while leaving room for expansion. Codes M48.52XA and X32.XXXA are examples of codes completed by addition of placeholders to fill the characters between the end of the subcategory listing and a required seventh character.
Guidelines and Conventions of the Alphabetic Index
The alphabetic index of ICD-10-CM consists of an alphabetic list of terms for diseases, injuries, and other reasons for encounters with their corresponding codes or code categories. It also includes an index to external causes of injuries, a table of neoplasms, and a table of drugs and chemicals. The alphabetic index contains main terms followed by a listing of terms that add specificity, such as acute or chronic. When a code appears next to a main term in the index, the code is a default code representing the condition most commonly associated with that term. This is often an "unspecified" code and should be reported only when information needed to arrive at a more specific code is not available.
Each main term in the index may be followed by a listing of subterms that further define the condition. The indents in the alphabetic index serve to guide the reader through the list of subterms, keeping each level of granularity connected back to the main term. Note that "with" is the first subterm in categories where it applies. The remaining subterms are in alphabetic order.
Example Adenoiditis (chronic) J35.02
– with tonsillitis J35.03
– acute J03.90
– recurrent J03.91
– specified organism NEC J03.80
– recurrent J03.81
– staphylococcal J03.80
– recurrent J03.81
In the example above, adenoiditis is the main term with an initial first subterm "with tonsillitis" followed by a second subterm "acute" followed by further levels of subterms to specify the organism involved and whether or not the acute adenoiditis is recurrent.
When consulting the alphabetic index, terms or subterms may be followed by a series of terms enclosed in parentheses. These are nonessential modifiers that may or may not be present in the documentation and do not affect the code number assigned.
ExamplesAsthma, asthmatic (bronchial) (catarrh) (spasmodic) J45.909 Agenesis
– adrenal (gland) Q89.1
Brackets are used in the alphabetic index to identify manifestation codes.
ExampleAmyloidosis (generalized) (primary) E85.9
– with lung involvement E85.4 [J99]
– familial E85.2
– genetic E85.2
– heart E85.4 [I43]
Manifestation codes are always sequenced second to the etiology codes. In the example above, code E85.4 represents organ-limited amyloidosis and secondary codes J99 or I43 indicate the manifestation in the lungs or heart. The descriptors for codes J99 and I43 include the phrase "in diseases classified elsewhere," indicating they are manifestation codes. In the tabular list, these codes appear with an instruction to code first the underlying disease.
Example I43 Cardiomyopathy in diseases classified elsewhere
Code first underlying disease, such as
glycogen storage disease (E74.0)
A dash (-) following a code in the alphabetic index indicates that the code is incomplete and that further characters must be located in the tabular list. Even where the dash is not present at the end of a code in the alphabetic index, the tabular list should be consulted for further instructions and possible seventh character requirements.
Example Index entry — Kearns-Sayre syndrome H49.81-
Tabular list — H49.81 Kearns-Sayre syndrome
Progressive external ophthalmoplegia with pigmentary retinopathy
Use additional code for other manifestation, such as: heart block (I45.9)
H49.811 Kearns-Sayre syndrome, right eye
H49.812 Kearns-Sayre syndrome, left eye
H49.813 Kearns-Sayre syndrome, bilateral
H49.819 Kearns-Sayre syndrome, unspecified eye
In the above example, the dash at the end of the index entry for Kearns-Sayre syndrome indicates that H49.81 is not a complete code. The tabular list provides the necessary sixth characters, indicating the involvement of one or both eyes and instruction to additionally report any manifestation such as heart block. ICD-10-CM captures laterality where it applies.
Terms in the index that include the abbreviation NEC for not elsewhere classified correspond to codes representing documented conditions other than those specified in ICD-10-CM. Think of NEC in the index as meaning other or other specified.
Example of NECAberrant (congenital) — see also Malposition, congenital
– artery (peripheral) Q27.8
– basilar NEC Q28.1
Q28.1 Other malformations of precerebral vessels
Congenital malformation of precerebral vessels NOS
Congenital precerebral aneurysm (nonruptured)
The abbreviation NOS for not otherwise specified corresponds to unspecified codes representing conditions for which documentation does not support a more specific code selection.
Example of NOSBirth
– compression during NOS P15.9
P15.9 Birth injury, unspecified
When an unspecified code is not provided in a category, the "other" code option represents both other and unspecified.
The alphabetic index also contains the instructions to "see" and "see also." The instruction "see" will be followed by another term that should be referenced in the index to arrive at the correct code. A "see also" instruction indicates that there is another main term that may provide additional alphabetic index entries related to the condition. It is not necessary to follow the see also note when the original main term provides the necessary code.
ExamplesAbandonment — see Maltreatment
Abnormal, abnormality, abnormalities — see also Anomaly
It is necessary to follow the instruction to "see Maltreatment" in the first example above. However, if the abnormality to be reported is represented in the subterms of the second example, the "see also Anomaly" instruction can be disregarded.
The instruction "see also" is used to guide selection of the correct column in the neoplasm table and to use of the table of drugs and chemicals for adverse effect, poisoning, underdosing, or toxic effects of drugs or chemicals. These tables are important references to code selection but, as with the alphabetic index, the tabular list remains the final step in code selection.
The neoplasm table lists the codes or code subcategories for neoplasms by anatomical site. For each site, 6 columns provide for selection by type of neoplasm: malignant primary, malignant secondary, carcinoma in situ, benign, uncertain behavior, or unspecified behavior. The alphabetic index provides the "see also" instructions referencing the correct column for the morphological varieties of neoplasms.
Example Diagnosis documented is neuroblastoma of right adrenal gland
Alphabetic index Neuroblastoma
– olfactory C30.0
– specified site — see Neoplasm, malignant, by site
Neoplasm table Site — Adrenal, gland
Malignant column C74.9-
Tabular list C74.9 Malignant neoplasm of unspecified part of adrenal gland
C74.90 Malignant neoplasm of unspecified part of unspecified adrenal gland
C74.91 Malignant neoplasm of unspecified part of right adrenal gland
C74.92 Malignant neoplasm of unspecified part of left adrenal gland
The alphabetic index provides direction to the malignant column of the neoplasm table. The neoplasm table provides the subcategory for the code but indicates the code is incomplete with a dash following the code number, C74.9-. The tabular list provides the choices for complete code selection, with C74.91 representing the right adrenal gland. (Further documentation of the site as capsule, cortex, or medulla of the adrenal gland would have resulted in a more specific code in this example.)
Similarly, the table of drugs and chemicals provides a list of codes or subcategories of codes by substance with columns indicating accidental poisoning, intentional self-harm poisoning, poisoning by assault, undetermined poisoning, adverse effect, and underdosing.
Example Documentation states overdose of amoxicillin due to parent error in administering dose
Alphabetic index Overdose, overdosage (drug) — see table of drugs and chemicals, by drug, poisoning
Table of drugs Drug — Amoxicillin, Poisoning, accidental T36.0X1
Tabular list T36 Poisoning by, adverse effect of and underdosing of systemic antibiotics
The appropriate seventh character is to be added to each code from category T36.
A — initial encounter
D — subsequent encounter
S — sequela
T36.0X Poisoning by, adverse effect of and underdosing of penicillins
T36.0X1 Poisoning by penicillins, accidental (unintentional)
Note that the index listing for overdose refers to the table of drugs and chemicals with a "see" instruction. The table of drugs and chemicals provides subcategory T36.0X1 but does not provide a complete code. The tabular list instructions at category T36 note that a seventh character must be added to indicate the type of encounter as initial, subsequent, or sequela to the poisoning. Selection of a code from the table alone would result in an invalid code.
The final part of the alphabetic index is the external cause of injuries index. External cause codes are intended to provide data for injury research and evaluation of injury prevention strategies. These codes capture the cause, intent, place of occurrence, activity of the patient at the time of the event, and patient status (eg, civilian, military). The selection of the appropriate external cause code is guided by the alphabetic index of external causes and by inclusion and exclusion notes in the tabular list. These codes are not required when the external cause is included in the code for the related condition, as in our example above for accidental poisoning by overdosing of ampicillin.
Example Documentation states this is the initial encounter with a patient who was injured due to being run over by a giraffe while cleaning its pen at the zoo. Codes for injuries sustained would be reported first followed by external cause codes.
Excerpted from Principles of Pediatric ICD-10-CM Coding by Jeffrey F. Linzer. Copyright © 2013 American Academy of Pediatrics. Excerpted by permission of American Academy of Pediatrics.
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