Updated on: November 21, 2016

Combination Codes and ICD-10

Original story posted on: June 22, 2015

It’s one of the most important questions coders must ask while using ICD-10: Is there a single combination code that fully identifies the patient’s relevant conditions, or is it necessary to report two separate codes? This question is also important in ICD-9; however, the volume of combination codes in ICD-10 has increased, making it imperative for coders to be alert and aware of instances in which combination codes are applicable.

Defining Combination Codes

The ICD-10-CM Official Guidelines for Coding and Reporting describe combination codes as those used to classify the following:

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

Coders cannot — and should not — assign multiple diagnosis codes when a single combination code clearly identifies all aspects of the patient’s diagnosis. For example, say a patient presents with obstructed and chronic cholecystitis with cholelithiasis and choledocholithiasis. Assign ICD-10 combination code K80.67 (calculus of gallbladder and bile duct with acute and chronic cholecystitis with obstruction). All components of the diagnostic statement are captured in this single code, and no additional codes are required.

Be on the lookout for instances in which the combination code lacks the necessary specificity to describe the manifestation or complication. In these instances, be prepared to assign an additional code. For example, say a physician provides a diagnostic statement of “undelivered mother in second trimester with Von Willebrand’s disease.” Assign ICD-10 code O99.112 (other diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism complicating pregnancy, second trimester) and ICD-10 code D68.0 (Von Willebrand’s disease).

The instructional notes throughout the tabular index remind coders when an additional code may be necessary. For example, the instructional note “use additional code to identify the specific condition” located under code category O99 reminds coders that they must assign a secondary code to identify any maternal diseases that complicate a pregnancy.

The alphabetic index also includes helpful hints. Look for subterms such as “with,” “due to,” “in,” or “associated with” to denote when a combination code may be applicable.

What’s Different in ICD-10

As mentioned above, combination codes are not a new concept, but they have been expanded in ICD-10. Consider these two important examples of new combination codes in ICD-10:

1. Diabetes mellitus. ICD-10 combination codes include both the diabetic manifestation as well as the diabetes itself. For example, say a physician provides a diagnostic statement of “type 1 diabetes complicated by gastroparesis.” In ICD-9, coders assign two codes — 250.61 (diabetes with neurological manifestations) and 536.3 (gastroparesis). In ICD-10, one single combination code, E10.43 (Type 1 diabetes mellitus with diabetic autonomic [poly]neuropathy), captures the entire encounter.

2. Conditions due to drugs, medicaments, and biological substances. ICD-10 combination codes denote whether the patient has experienced a poisoning, adverse effect, or underdosing as well as the specific substance responsible for the outcome. For example, say a patient presents with an accidental heroin overdose. In ICD-9, coders assign two codes — 965.01 (poisoning by heroin) and E850.0 (accidental poisoning by heroin). In ICD-10, one single combination code (T40.1X1A, poisoning by heroin, accidental [unintentional]) captures the entire encounter.

Tips for Compliance

Consider these tips to ensure accurate application of combination codes:

  • Review the diagnostic statement carefully to determine whether a combination code may be applicable. The encoder will help guide coders; however, it’s also helpful to check the alphabetic and tabular indices to look for any instructional notes that may be applicable.
  • Review ICD-10 code categories E10 (Type 1 diabetes mellitus), E11 (Type 2 diabetes mellitus), and E13 (other specified diabetes mellitus). Familiarize yourself with combination codes for each type of diabetes, including what documentation may be necessary.
  • Review ICD-10 code category T36-T50 (poisoning by, adverse effects of, and underdosing of drugs, medicaments, and biological substances). Familiarize yourself with combination codes in this category as well as what additional codes may be necessary.
  • Scan other chapters of the ICD-10 book and circle combination codes that you may report frequently and that previously required two separate codes in ICD-9. Consider these examples:
    • ICD-10 code I25.110 (arteriosclerotic heart disease of native coronary artery with unstable angina pectoris). In ICD-9, coders must report both 414.01 (coronary arteriosclerosis of native coronary artery) and 411.1 (intermediate coronary syndrome) to denote this condition.
    • ICD-10 code A69.23 (arthritis due to Lyme disease). In ICD-9, coders must report both 088.81 (Lyme disease) and 711.89 (arthropathy associated other infectious and parasitic diseases) to denote this condition.
  • Don’t be afraid to query. When coders suspect that a combination code may be applicable, but documentation doesn’t clearly link the two diagnoses, query the physician for more information. In some cases, the physician must state clearly that a condition is “due to” another condition. For example, say a patient is admitted with a gastrointestinal (GI) bleed. Upon evaluation with EGD and colonoscopy, the patient is found to have acute gastritis, duodenal angiodysplasia, and diverticulosis. The physician doesn’t identify the source of the GI bleed. All three conditions can cause bleeding, and all three conditions have a combination code that includes bleeding. Coders must query the physician to determine the etiology of the GI bleed, if known.  

As we all continue to focus on coding productivity in ICD-10, it’s also imperative to ensure data quality and integrity. Don’t be tempted to rush through a record just for the sake of meeting productivity standards. Coders must take their time and identify instances in which combination codes are applicable. When coders incorrectly report two separate codes rather than a single combination code, not only does data quality suffer, but reimbursement also could be at risk.

Omitting a complication entirely also can have a negative effect on quality and reimbursement. Familiarize yourself now with the combination codes you anticipate reporting most frequently, and be on the lookout for others.



Disclaimer: Every reasonable effort was made to ensure the accuracy of this information at the time it was published. However, due to the nature of industry changes over time we cannot guarantee its validity after the year it was published.
Cathie Wilde, RHIA, CCS

Cathie Wilde, RHIA, CCS, is the director of coding services for MRA. Ms. Wilde has been active in the healthcare industry for more than 30 years. Her previous positions have included assistant director of HIM, DRG coordinator at the Massachusetts Hospital Association, and DRG validator at Blue Cross Blue Shield. She has extensive experience in ICD-9-CM and CPT coding, auditing, data analysis, development and testing of coding products, specialized reporting, and in-service training. As director she is responsible for overseeing the coding division, providing the strategic direction of MRA as a local industry leader of quality coding, auditing, and denial management services. Ms. Wilde is an American Health Information Management Association (AHIMA)-approved ICD-10-CM/PCS trainer.

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