General Coding Guidelines for ICD-10-CM

ICD-10-CM Basics

Selecting accurate diagnosis codes using ICD-10-CM is challenging due to the availability of more than 68,000 codes. In this blog, we shared general coding guidelines for ICD-10-CM, which will help you select accurate diagnosis codes. Before we proceed with coding guidelines, you’ll need access to two lists in ICD-10 CM: the Alphabetical Index of diagnostic terms and the Tabular List of ICD-10 codes.

The Alphabetical Index of diagnostic terms lists thousands of ‘main terms’ alphabetically. Under each of those main terms, there is often a sub-list of more detailed terms; for instance, ‘Cataract’ has a sub-list of 84 terms. The Tabular List of ICD-10 codes is organized alphanumerically from A00.0 to Z99.89. It is divided into chapters based on body parts or conditions.

General Coding Guidelines for ICD-10-CM

Locating a code in the ICD-10-CM 

To select a code in the classification corresponding to a diagnosis or reason for a visit documented in a medical record, locate the term in the Alphabetic Index and then verify the code in the Tabular List.

Read and be guided by instructional notations in the Alphabetic Index and the Tabular List. It is essential to use both the Alphabetic Index and Tabular List when locating and assigning a code.

The Alphabetic Index does not always provide the complete code. The entire code, including laterality and any applicable 7th character, can only be selected in the Tabular List.

A dash (-) at the end of an Alphabetic Index entry indicates that additional characters are required. Even if a dash is not included in the Alphabetic Index entry, referring to the Tabular List is necessary to verify that no 7th character is required.

Level of Detail in Coding 

Diagnosis codes are to be used and reported at the highest number of characters available and to the highest level of specificity documented in the medical record. ICD-10-CM diagnosis codes are composed of 3, 4, 5, 6, or 7 characters.

Codes with three characters are included in ICD-10-CM as the heading of a category of codes that may be further subdivided by using fourth, fifth, or sixth characters, which provide greater detail.

A three-character code will be used only if not further subdivided. If applicable, a code is invalid if it has not been coded to the total number of characters required for that code, including the 7th character.

Multiple Coding for a Single Condition 

In addition to the etiology/manifestation convention that requires two codes to describe a single condition that affects multiple body systems entirely, other single conditions also need more than one code. ‘Use additional code’ notes are found in the Tabular List for codes not part of an etiology/manifestation pair where a secondary code is helpful in fully describing a condition.

The sequencing rule is the same as the etiology/manifestation pair. ‘ Use additional code’ indicates that a secondary code should be added if known. 

Combination Code 

A combination code is a single code used to classify two diagnoses: a diagnosis with an associated secondary process (manifestation) or an associated complication. Combination codes are identified by referring to sub-term entries in the alphabetic index and reading the inclusion and exclusion notes on the tabular list.

Assign only the combination code when that code fully identifies the diagnostic conditions involved or when the Alphabetic Index directs. Multiple coding should not be used when the classification provides a combination code that identifies all the elements documented in the diagnosis.

When the combination code lacks specificity in describing the manifestation or complication, an additional code should be used as a secondary code.

Sequela (Late Effects) 

A sequela is a residual effect (condition produced) after the acute phase of an illness or injury has terminated. There is no time limit on when a sequela code can be used. The residual may be apparent early, such as in cerebral infarction, or it may occur months or years later due to a previous injury.

Examples of sequela include scar formation resulting from a burn, deviated septum due to a nasal fracture, and infertility due to tubal occlusion from old tuberculosis. Coding of sequela generally requires two codes sequenced in the following order: the condition or nature of the sequela is sequenced first. The sequela code is sequenced second.

Use of Sign/Symptom/Unspecified Codes 

Sign/symptom and ‘unspecified’ codes have acceptable, even necessary, uses. While specific diagnosis codes should be reported when supported by the available medical record documentation and clinical knowledge of the patient’s health condition, there are instances when signs/symptoms or unspecified codes are the best choices for accurately reflecting the healthcare encounter. Each healthcare encounter should be coded to the level of certainty known for that encounter. 

Impending or Threatened Condition 

Code any condition described at the time of discharge as ‘impending’ or ‘threatened’ as follows: 

• If it did occur, code it as the confirmed diagnosis. 
• If it did not occur, reference the Alphabetic Index to determine if the condition has a subentry term for ‘impending’ or ‘threatened’ and also reference primary term entries for “Impending” and ‘Threatened.’
• If the sub-terms are listed, assign the given code. 
• If the sub-terms are not listed, code the existing underlying condition(s), not the condition described as impending or threatened.

Remaining Coding Guidelines for ICD-10-CM

Here are some additional important guidelines to keep in mind when coding with ICD-10-CM:

• The appropriate codes from A00.0 through T88.9, Z00-Z99.8, and U00-U85 must be used to identify diagnoses, symptoms, conditions, problems, complaints, or other reason(s) for the encounter/visit.
• Codes that describe symptoms and signs, as opposed to diagnoses, are acceptable for reporting purposes when the provider has not established a related definitive diagnosis.
• Signs and symptoms associated routinely with a disease process should not be assigned as additional codes unless otherwise instructed by the classification.
• Additional signs and symptoms that may not be associated routinely with a disease process should be coded when present.
• If the same condition is described as acute (sub-acute) and chronic, and separate subentries exist in the Alphabetic Index at the same indentation level, code both and sequence the acute (sub-acute) code first.
• Each unique ICD-10-CM diagnosis code may be reported only once for an encounter. This applies to bilateral conditions when no distinct codes identify the same ICD-10-CM diagnosis code classifies laterality or two different situations.
• Some ICD-10-CM codes indicate laterality, specifying whether the condition occurs on the left, right, or is bilateral. If no bilateral code is provided and the condition is bilateral, assign separate codes for both the left and right sides. If the side is not identified in the medical record, assign the code for the unspecified side.
• If the provider documents a ‘borderline’ diagnosis at the time of discharge, the diagnosis is coded as confirmed unless the classification provides a specific entry (e.g., borderline diabetes). If a borderline condition has a particular index entry in ICD-10-CM, it should be coded as such. Since borderline conditions are not uncertain diagnoses, no distinction is made between the care setting (inpatient versus outpatient). 

Medical Billers and Coders (MBC) is a leading medical billing company that provides complete billing and coding services. For provider education purposes, we shared general coding guidelines for ICD-10-CM. The following link provides a detailed explanation.

In case any assistance is needed for medical billing and coding, contact us at 888-357-3226 / info@medicalbillersandcoders.com

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