How to Identify and Apply ICD-10 Combination Codes

by | Published on Jan 18, 2018 | Resources, Medical Coding News (A) | 0 comments

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With 363 new codes, 142 deletions, and 226 code revisions made to the ICD-10 code set this FY, diagnostic coding has become even more challenging. As medical coding service providers know, knowing how to use combination codes is a key aspect in reducing the complexity of ICD-10 coding. Importantly, reporting them correctly is necessary to avoid claim denials.

Combination codes allow for the reporting of a single code to express multiple aspects of the diagnosis. The ICD-10-CM Official Guidelines for Coding and Reporting describe a combination code as one used to classify the following:

  • Two diagnoses
  • A diagnosis with an associated secondary process (manifestation)
  • A diagnosis with an associated complication

In ICD-10, combination codes identify both the definitive diagnosis and common symptoms of that diagnosis. When using a combination code, an additional code should not be assigned for the symptom.

Combination Codes – ICD-9 versus ICD-10

Technically, this is similar to the way ICD-9 defined combination codes. However, ICD-10 expands on the use of combination codes. Consider the following examples:

  • Lower back pressure ulcer, stage II could be reported inICD-9 using two codes-707.03 Pressure ulcer, lower back and 707.22 Pressure ulcer stage II. Under ICD-10, however, a single code is used to depict the condition -132 Pressure ulcer of right lower back, stage 2. Thus, ICD-10 pressure ulcer codes are combination codes that include:
    • the site (lower back) of the pressure ulcer
    • the location (right/left) of the pressure ulcer, and
    • the stage of the pressure ulcer
  • For reporting Type 2 diabetes with mild nonproliferative retinopathy with macular edema, ICD-9 required three distinct codes:
    • 250.52 Type 2 diabetes with ophthalmic manifestations
    • 362.04 Mild nonproliferative diabetic retinopathy
    • 362.07 Diabetic macular edema

    However, if a patient presents with all of these conditions, only one code is required in ICD-10:

    E11.321 Type 2 diabetes mellitus with mild nonproliferative diabetic retinopathy with macular edema

  • For conditions due to drugs, medicaments, and biological substances, ICD-10 combination codes indicate whether the patient has experienced a poisoning, adverse effect, or underdosing as well as the specific substance responsible for the outcome. For example, in ICD-9, accidental heroin overdose requires two codes – 965.01 (poisoning by heroin) and E850.0 (accidental poisoning by heroin). In ICD-10, the entire encounter is assigned a single combination code – T40.1X1A, poisoning by heroin, accidental (unintentional).
  • Other examples of combination codes in ICD-10:
    • I26.01 Septic pulmonary embolism with acute cor pulmonale
    • K57.21 Diverticulitis of large intestine with perforation and abscess with bleeding
    • E11.341 – Type 2 diabetes mellitus with severe nonproliferative diabetic retinopathy with macular edema
    • E10.21 Type 1 diabetes mellitus with diabetic neuropathy
    • I25.110 Atherosclerotic heart disease of native coronary artery with unstable angina pectoris
    • K80.67 Calculus of gallbladder and bile duct with acute and chronic cholecystitis with obstruction
    • K71.51 Toxic liver disease with chronic active hepatitis with ascites

Points to Note

  • ICD-10 has more combination codes than ICD-9
  • ICD-10 combination codes provide more specific information
  • These specific, concise codes require more detailed physician documentation
  • Additional specificity requires the medical coding service provider to focus on abstracting information from the medical record
  • ICD-10 guidelines state that multiple diagnosis codes should not be reported when a single combination code clearly identifies all aspects of the patient’s diagnosis.
  • If the combination code lacks necessary specificity in describing the manifestation or complication, an additional code should be used as a secondary code.

Identifying and Applying Combination Codes

Combination diagnoses can be found in the Alphabetic Index by locating the primary condition and using the subterm entries to narrow the search. If the subterms include words such as “with,” “due to,” “in” or “associated with” to tie two diagnoses together, this would be a clear indicator of a combination code. Referring to the inclusion and exclusion notes in the Tabular List would provide additional clues on the matter.

Experienced coders in medical coding companies understand ICD-10 coding guidelines and would know when only one code should be reported. To determine whether a combination code might exist, they will determine:

  • Whether the disease processes are linked
  • The root cause of a particular disease

Combination codes will used only when they meet the following criteria:

  • The Alphabetic Index specifically lists them to match the primary diagnosis.
  • The code fully describes the diagnostic conditions in the clinical documentation.

To illustrate this, an article in offers the example of a patient who presents with toxic liver disease, chronic active hepatitis, and ascites. Expert coders would recognize that toxic liver disease is associated with the hepatitis and that the two disease processes occur together along with a manifestation (ascites). They would report the condition correctly using combination code K71.51 Toxic liver disease with chronic active hepatitis with ascites.

Experienced coders can ease the challenges involved in reporting these complex combination codes. They are familiar with:

  • Combination codes frequently used for diagnoses such as diabetes – E10 (Type 1), E11 (Type 2), and E13 (Other specified), as well asT36-T50 Poisoning by, adverse effects of and underdosing of drugs, medicaments, and biological substances
  • Documentation requirements
  • Additional codes that may be needed

Reliable coders will query the physician if they find that a combination code may be applicable, but documentation does not clearly link the two diagnoses. If the condition is “due to” another condition, the physician’s documentation must indicate this. Expert medical billing and coding services can go a long way in helping physicians to ensure compliance, prevent denials, and maximize reimbursement.

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