Revenue Cycle Insider

Hint: Look at your ICD-10-CM long-term drug use appendix.

Whether you’re coding the long-term use of a drug targeting a specific cancer, a drug targeting a condition caused by the cancer, a drug targeting the side effects of a cancer drug, or a drug prescribed for a pre- or post-cancer patient, there’s a good chance that you are often reaching for a Z79.- (Long term (current) drug therapy) code.

But while you can often assign a specific code for a specific drug quickly and easily, sometimes code assignments for long-term drug use can get sticky. So, here are a few dos and don’ts you should consider before assigning a Z79.- code for long-term drug use.

Do Understand What ICD-10-CM Means by “Long-Term”

ICD-10-CM does not specify a timeframe for assigning any code from Z79.-. However, you should “assign a code from Z79 if the patient is receiving a medication for an extended period as a prophylactic measure (such as for the prevention of deep vein thrombosis) or as treatment of a chronic condition (such as arthritis) or a disease requiring a lengthy course of treatment (such as cancer),” per guideline I.C.21.c.3.

Alternatively, the guideline also says you should not assign a code from Z79.- “for medication being administered for a brief period of time to treat an acute illness or injury (such as a course of antibiotics to treat acute bronchitis).”

In other words, you’ll assign a Z79.- code if the patient is taking a drug over an extended period (“long-term”) for a chronic condition, and the patient is taking the medication at the time of the encounter (“current”).

Do Understand How the Codes Are Broken Down

You’ll find codes pertaining to long-term cancer drug use broken down by therapy type, mostly under Z69.6- (Long term (current) use of immunomodulators and immunosuppressants) and Z79.81- (Long term (current) use of agents affecting estrogen receptors and estrogen levels), where you’ll find many of the breast and prostate cancer drug therapies listed.

So, under Z79.63 (Long term (current) use of chemotherapeutic agent), you’ll find the following therapies:

• Z79.630 (Long term (current) use of alkylating agent)
• Z79.631 (Long term (current) use of antimetabolite agent)
• Z79.632 (Long term (current) use of antitumor antibiotic)
• Z79.633 (Long term (current) use of mitotic inhibitor)
• Z79.634 (Long term (current) use of topoisomerase inhibitor)

For further study: Medline plus has a comprehensive guide to chemotherapy types, the cancers they treat, and commonly used drugs. The American Cancer Society also has similar guides for aromatase inhibitors and selective estrogen receptor modulators (SERMs).

Do Pay Attention to the Codes’ Inclusion Terms

Fortunately, you don’t have to know a lot about the types of cancer drug therapies to arrive at the correct long-term drug use code. Most of the codes have lists of inclusion terms that include the drug name and, often, its brand name. So, the inclusion terms tell you to code patients taking leuprolide acetate (leuprorelin) or Lupron on a long-term basis to treat prostate cancer, or fulvestrant (Faslodex) for breast cancer, to Z79.818 (Long term (current) use of other agents affecting estrogen receptors and estrogen levels).

Don’t Ignore the ICD-10-CM Long-Term Drug Use Appendix

The inclusion terms listed under the long-term drug codes are not comprehensive, however. The Medline guide referred to above notes there are over 100 different chemotherapy medicines alone. This means you may have to do a little bit of research before assigning a long-term drug use code.

Fortunately, ICD-10-CM code books include an appendix that lists many cancer drugs and matches them with the correct long-term drug use code.

Example: Z79.632 (Long term (current) use of antitumor antibiotic) lists three drugs, bleomycin, doxorubicin, and mitomycin C. However, daunorubicin is another anthracycline antibiotic used in cancer therapy that should also be classified under Z79.632. Searching for the drug in the appendix will lead you to that code and enable you to correctly classify it.

But you should use the appendix with caution, as it is also not a comprehensive list. AAPC’s ICD-10-CM code book Appendix A notes this and tells you to consult with payers for correct long-term drug use coding and billing.

For further study: The National Cancer Institute maintains a comprehensive A to Z list of cancer drugs.

Do Pay Attention to the Code Instructions

Once you’ve assigned the correct long-term drug therapy code, you need to make sure you follow one very important instruction that pertains to all the Z79.- codes, and that is to code also any therapeutic drug level monitoring using Z51.81 (Encounter for therapeutic drug level monitoring). It’s an instruction that makes sense, as oncologists will want to measure the efficacy — and possible toxic effects — of the therapy they are administering to their patients.

Then, under Z79.81, you’ll find further instructions. They tell you to Code first C50.- (Malignant neoplasm of breast) or C61 (Malignant neoplasm of prostate) as appropriate. You’ll also find Use additional code instructions to code for genetic susceptibility to malignant neoplasm, personal and/or family history of breast or prostate cancer, and Z17.0 (Estrogen receptor positive status [ER+]) along with Z78.0 (Asymptomatic menopausal state) as appropriate. All these instructions make sense, as they help to justify the long-term use of agents to control estrogen receptors in treating breast or prostate cancer.

The code also contains an Excludes1 note that tells you not to use Z79.81- when the drugs are being used instead for hormone replacement therapy, coded to Z79.890 (Hormone replacement therapy).

Do Understand Why You Should Report a Z79.- Code

Even though ICD-10-CM does not require you to report Z79.- codes, there are two good reasons why you should:

1. Supporting a high MDM level: Z79.- codes can play an important role in helping to determine high-level medical decision making (MDM) for an office/outpatient evaluation and management (E/M) visit. That’s because drug therapy requiring intensive monitoring for toxicity is an example of high MDM level in the Risk of Complications element of MDM. So, a Z79.- code can play a role in helping to justify the complexity of the MDM involved in the patient’s care.
2. Supporting medical necessity for testing and treatment: Assigning the appropriate Z79.- code will justify lab testing your provider may order to monitor the efficacy and safety of the specific drug therapy being administered to the patient.

Bruce Pegg, BA, MA, CPC, CFPC, Managing Editor, AAPC