Question: How do I code a patient with strep throat, tonsillitis, and a peritonsillar abscess? Michigan Subscriber Answer: Coding the peritonsillar abscess portion of this diagnosis is simple. However, in order to reach the correct set of codes, you’ve got to make sure you adhere to the instructions listed underneath the primary diagnosis. First, you will use the index to determine that a peritonsillar abscess is coded as J36 (Peritonsillar abscess). Next, you must take a look at both the “Use Additional” and “Excludes1” notes underneath J36. According to the ICD-10-CM guidelines, you should “Use additional code (B95-B97) to identify infectious agent.” You will use a code from this section to report the streptococcal infectious origin code. Strep throat is classified under streptococcus group A, therefore the correct B code is B95.0 (Streptococcus, group A, as the cause of diseases classified elsewhere). As for the strep throat diagnosis, there are a few different routes you can take. While you won’t find “strep throat” anywhere in the index, you will find the correct code by searching under its scientific name, streptococcal pharyngitis. Under Pharyngitis ⇒ streptococcal, you will reach code J02.0 (Streptococcal pharyngitis). Finally, you should not add an additional diagnosis code of tonsillitis due to the “Excludes1” note underneath J36. A “Type 1 Excludes” note means that you should not report any terms listed underneath the note alongside the primary diagnosis. In this case, both J35.0- (Chronic tonsillitis and adenoiditis) and J03.9- (Acute tonsillitis, unspecified) are listed underneath the “Excludes1” note.