Otolaryngology Coding Alert

Question: What’s the diagnosis coding for a patient experiencing an allergic reaction (vomiting, rashes) to azithromycin following treatment for an ear infection? The patient stated that they did not finish the five-day cycle following the reactions.

Washington Subscriber

Answer: To code this scenario correctly, you first need to consult ICD-10-CM guidelines for Adverse Effects, Poisoning, Underdosing and Toxic Effects — specifically Section I.C.19.e.5.a. The guideline tells you that, “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).”

This means you will first code for the “nature of the adverse effect” by reporting R11.10 (Vomiting, unspecified) for the vomiting. For the rash, however, you should avoid the temptation to use another signs and symptoms code and skip over R21 (Rash and other nonspecific skin eruption). That’s because the term “rash” in the ICD-10-CM Alphabetic Index breaks down by cause, and you are directed to use L27.0 (Generalized skin eruption due to drugs and medicaments taken internally) for a rash caused by internally consumed drugs or medications.

For your final code assignment, you’ll need to head to the T36-T50 codes as the ICD-10-CM guideline instructs. Specifically, you’ll report a code from category code T36.- (Poisoning by, adverse effect of and underdosing of systemic antibiotics) as the patient’s provider correctly prescribed and properly administered the azithromycin, an antibiotic.

The T36.- codes are further broken down by antiobiotic type. As azithromycin is classed as a macrolide, you’ll narrow your code choice down to T36.3- (Poisoning by, adverse effect of and underdosing of macrolides). To complete the code, you’ll then need to follow the instruction accompanying the T36.- code group, which tells you to add the appropriate 7^th character. This means adding a 5^th character, placeholder X; a 6^th character, 1, to indicate the adverse effect of the antibiotic was accidental or unintentional; and a 7^th character, A, to indicate this was the patient’s first encounter with the provider for the issue.

Putting it all together: The correct diagnosis codes for the encounter should be:

• R11.10
• L27.0
• T36.3X1A (Poisoning by macrolides, accidental (unintentional), initial encounter)

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