Health Information Management

Get ready for ICD-10-CM combination codes

JustCoding News: Outpatient, November 16, 2011

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Coders well versed in ICD-9-CM know that a combination code is a single code used to classify one of the following:

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

ICD-10-CM technically defines combination codes the same way. However, the codes take on an entirely different flavor. Not only does ICD-10-CM include more of them, but they often provide more specific information. This additional specificity requires coders to place greater emphasis on abstracting information from the medical record.

Consider pressure ulcers. Coders using ICD-9-CM must assign two codes—one for the site of the ulcer and another for the stage. Conversely, ICD-10-CM includes nearly six pages of pressure ulcer combination codes (category L89) that identify the site and stage of an ulcer and laterality—all in one code. For example, ICD-10-CM code L89.013 denotes pressure ulcer of the right elbow, stage 3. As with ICD-9-CM, coders may derive the stage of an ulcer from wound care or nursing notes. However, coders must base the actual diagnosis and site (including laterality) on physician documentation.

Upon quick glance, many ICD-10-CM combination codes demonstrate conciseness that will facilitate research, medical necessity, and denial ¬management. For example, a patient presents with type 2 diabetes with mild nonproliferative retinopathy with macular edema. Coders using ICD-9-CM must report the following three separate codes to capture this information:

  • 250.52 (type 2 diabetes with ophthalmic manifestations)
  • 362.04 (mild nonproliferative diabetic retinopathy)
  • 362.07 (diabetic macular edema)

However, with ICD-10-CM, only one code—E11.321 (type 2 diabetes mellitus with mild nonproliferative diabetic retinopathy with macular edema)—is necessary. This code denotes the type of diabetes mellitus, the body system affected, and the specific complications affecting that body system.

These combination codes exemplify the impressive specificity that ICD-10-CM offers.
Further, these more specific and concise codes will require more specific physician documentation, says Donna Smith, RHIA, senior consultant at 3M in Atlanta.

In some cases, physicians may not be accustomed to documenting in such detail, Smith explains. For example, a patient presents with an acute gout flare. Coders currently assign ICD-9-CM code 274.01 to capture this information. However, assigning a complete ICD-10-CM code will require that they know the specific cause of gout and link it to a specific joint, she says. For example, ICD-10-CM code M10.061 denotes idiopathic gout of the right knee.

"Interestingly enough, ICD-10 uses the term ‘idiopathic' a lot. It basically means due to an unknown cause," says Smith. "But unless the physician tells us that, we'd have to query or report it as unspecified."

Research the etiology of diseases
Understanding the etiology of a disease process will be paramount when thinking about combination codes, says Jean Bishop, MSPh, MBA, RHIT, CPC, CFE, CPhT, an independent consultant in Arlington, VA. For example, ICD-10-CM includes combination codes for atherosclerotic heart disease with angina pectoris. The subcategories for these codes are:

  • I25.11 (atherosclerotic heart disease of native coronary artery with angina pectoris)
  • I25.7 (atherosclerosis of coronary artery bypass graft[s] and coronary artery of transplanted heart with angina pectoris)

Assigning a separate code for angina pectoris is unnecessary because it's included in the combination code. ICD-10-CM guidelines state that coders can assume a causal relationship between atherosclerosis and angina pectoris unless documentation indicates the angina is due to something other than atherosclerosis.

Coders should remember that although unstable angina (a CC) is included in the combination code and not separately reported, it will continue to affect MS-DRG calculation, says Smith.

How to identify combination codes
One of the most challenging aspects of combination codes is simply knowing they even exist, says Bishop. For example, a patient has toxic liver disease, chronic active hepatitis, and ascites. Coders using ICD-9-CM don't report a combination code. Instead, they report 573.9 (toxic liver disease), 571.49 (chronic active hepatitis), and 789.59 (ascites).

However, coders using ICD-10-CM must recognize that they should report only one code—combination code K71.51 (toxic liver disease with chronic active hepatitis with ascites). Coders must understand that the toxic liver disease is associated with the hepatitis and that the two disease processes occur together along with a manifestation (ascites), says Bishop. The best way to locate this code is to start with the term "disease," then the subterm "liver" followed by "toxic, with hepatitis, chronic, active, with ascites," she explains.

When determining whether a combination code might exist, Smith says coders should ask these two questions:

  • Are the disease processes linked?
  • What is the root cause of a particular disease?

Coders must use combination codes when they are available, says Bishop. "The guidelines state that multiple codes should not be used when you clearly have a combination code that identifies all of the elements in the diagnosis," she says.

What you can do now
Hospitals can begin preparing for ICD-10-CM combination codes now. For example, streamline the query process and obtain physician buy-in so that the process works for both coders and physicians, says Bishop. Establishing a robust query process now will improve documentation and likely lead to fewer queries in the future, she says.

In addition, beware of unspecified codes. Even though unspecified codes exist in ICD-10-CM, Bishop fears that coders may default to these codes based on insufficient documentation. She sees this as a potential problem generally and especially with combination codes. Defaulting to unspecified ICD-10-CM codes could lead to noncoverage when insurers stop paying for services that could reasonably be better defined, Bishop says.

"There are concerns that claims will be rejected and need to be appealed," she says.

A high volume of unspecified codes could also lead to poor data collection for health plan analyses and public health purposes. Hospitals may also be more vulnerable to recovery audit contractor (RAC) audits if they default to unspecified codes rather than take advantage of ICD-10's inherent granularity and specificity, Bishop says. RACs may question why the provider was unable to obtain the appropriate details, she explains.

Coders also need ample training with respect to anatomy, physiology, and the etiology of diseases, says Smith. This knowledge will help coders ask more intelligent and clinically sound queries, she says. For example, coders may be able to more easily distinguish between conditions that typically are related and scenarios in which one condition typically causes another.

Even if a physician doesn't link two conditions, a coder would recognize the need to query and correctly assign the combination code.

Coders should include physicians in the educational process when possible, says Smith. For example, ask an orthopedic physician to share information about musculoskeletal procedures and diagnoses (e.g., the anatomy of a joint). Coders can then explain how codes related to this specialty will change in ICD-10-CM. Together, physicians and coders can brainstorm ways to best capture the information, she says.

Also remember that practice makes perfect, Bishop says. Review records that would require combination codes under ICD-10 (e.g., diabetes, coronary artery disease, pressure ulcers, and poisonings and adverse effects), she says.

Training and preparation for ICD-10 should include coding records with both ICD-9-CM and ICD-10-CM. Coders also should note opportunities for CDI.

Combination codes to ponder
Some ICD-10-CM combination codes that may surprise coders include the following:

  • Codes in categories T36–T65, which are combination codes that include substances related to adverse effects, poisonings, toxic effects and underdosing, and external causes (e.g., T39.011A, poisoning by aspirin, accidental [unintentional], initial encounter)
  • Combination external cause codes that identify sequential events that result in an injury, such as a fall which results in striking an object (e.g., W01.111A, fall on same level from slipping, tripping, and stumbling with subsequent striking against power tool or machine, initial encounter)

Editor’s note: This article was originally published in the November issue of Briefings on Coding Compliance Strategies. E-mail your questions to Contributing Editor Lisa Eramo at


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