ICD 10 Coding Alert

Question: A patient arrives for an evaluation and management (E/M) visit following chemotherapy for metastatic squamous neck cancer. The reason for the visit states "throat pain from vomiting following chemotherapy." What ICD-10 code(s) should I apply?

South Dakota Subscriber

Answer: When determining the proper ICD-10 code for an adverse effect, context is absolutely key. Many coders are guilty of improperly coding scenarios where patients experience adverse effects following chemotherapy.

However, in order to code this scenario correctly, you need to have a firm grasp on the known side effects of chemotherapy. Since vomiting and nausea are typical side effects for patients being administered chemotherapy, you will take a different route of coding this situation than if the effects were unintended. Take a look at section I.C.1.9 Adverse effects, poisoning, underdosing and toxic effects in the 2018 ICD-10 guidelines:

"When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug (T36-T50). The code for the drug should have a 5th or 6th character "5" (for example T36.0X5-) Examples of the nature of an adverse effect are tachycardia, delirium, gastrointestinal hemorrhaging, vomiting, hypokalemia, hepatitis, renal failure, or respiratory failure."

Based on these guidelines, you should code the vomiting first, followed by the adverse effect of the chemotherapy code. For vomiting, you will apply code R11.10 (Vomiting, unspecified) and for adverse effect of the chemotherapy, you will apply code T45.1X5A (Adverse effect of antineoplastic and immunosuppressive drugs, initial encounter). Despite the fact that the throat pain is the underlying reason for the visit, the throat pain is a result of the vomiting. ICD-10 guidelines state that, "if a causal condition is known, then the code for that condition should be sequenced as the principal or first-listed diagnosis." Since throat pain is not a typical symptom of vomiting, you may include R07.0 (Pain in throat) as a third and final diagnosis.

In order to find the adverse effect code, you should first open up the Table of Drugs and Chemicals section in ICD-10-CM book. There, you can search under the terms "antineoplastic," "immunosuppressive," or "cancer chemotherapy drug regimen" to find the correct set of codes. You will then select the code listed under "Adverse effect."

Careful:  You do not want to use the code listed under "Poisoning, accidental unintentional." Since the correct drug and the correct dosage was administered, these effects are a known and expected result of chemotherapy treatment. If, on the other hand, the patient received a much greater dosage than the doctor had prescribed, you could apply code T45.1X1A (Poisoning by antineoplastic and immunosuppressive drugs, accidental (unintentional), initial encounter).