Flu season is upon us and now would be a good time to discuss the coding of Influenza. There is some confusion when coding Influenza A and Novel Influenza A.
Let's start with the identifying and coding of Influenza A.
Influenza A is just plain documented influenza. This is coded to category J10, Influenza due to other identified virus and if the influenza is due to an unidentified influenza virus we assign a code from category J11, Influenza due to unidentified influenza virus.
A nasal swab is usually taken to diagnose Influenza A.
2018 AHA Coding Handbook, Chapter 19, "Influenza" page. 228
Novel Influenza A
Novel Influenza A is either H1N1 or H5N1. These are both animal-born influenzas and they can be either Avian (bird) or swine (pig) in origin. If documented, we assign a code to category J09. Influenza of other animal origin, not bird or swine is also coded to this category.
Per Coding Clinic, 3rd Qtr. 2016, page 11: "Codes from subcategory J09.X-, Influenza due to identified novel influenza A virus, are intended for a specific strain of influenza A, such as "novel" influenza A, and not the ordinary seasonal influenza A."
Coding Clinic, 3rd Qtr. 2016, page 11.
Confirmed / Suspected / Possible / Probable
CODE ONLY CONFIRMED CASES of Influenza due to certain identified influenza viruses, category J09 and due to other identified influenza virus, category J10. This is an exception to the hospital inpatient guideline Section II, H. (Uncertain Diagnosis). Confirmation does not require documentation of a positive laboratory test specific for avian or other novel influenza A or other identified influenza virus. Coding should be based on the provider’s diagnostic statement that the patient has avian influenza, or other novel influenza A, for category J09, or has another particular identified strain of influenza, such as H1N1 or H3N2, but not identified as novel or variant, for category J10.
If avian, novel, or other identified influenza is documented as being "suspected", "possible", or "probable" assign the appropriate code from category J11, Influenza due to unidentified influenza virus.
ICD-10-CM Official Coding Guidelines, S.1.C.10.c.