Q&A: Code to support medical necessity for lab testing during chemotherapy

Q: We are considering using of ICD-10 code Z79.899 (Other long term (current) drug therapy) to support medical necessity for lab testing while a patient is having chemotherapy. I am struggling with the definition of long-term and cannot find documentation to clarify what is considered long term where this code is concerned. Is it six weeks, three months, a year?

A: 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). Do not assign a code from category 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).

Editor's note: This question can be found in the Coding and Documentation category on the NAHRI Forums where you can find answers to questions on a variety of topics from billing and claims to compliance to reimbursement. Question answered by NAHRI Advisory Board member Ron Hirsh, MD, FACP, CHCQM, citing ICD-10-CM Official Guidelines for Coding and Reporting FY 2016, p. 84.