ICD 10 Coding Alert

Hint: Remember to reference different parts of your code book.

Coders may feel confident selecting and reporting primary diagnoses in the outpatient setting, but navigating coding guidelines to report secondary diagnoses can get a bit hairy, especially when different resources appear to provide different or even conflicting guidance.

Here are some expert tips about utilizing reference resources from Brett Randolph, RHIT, CDIP, CCS, vice president of client services at HIAcode, which he shared in his AAPC HEALTHCON 2025 presentation “[AHA] Coding Clinic^® Advice’s Impact on Reporting Additional Diagnoses in the Outpatient Setting.”

Documentation Is Still the Foundation

Coders are obviously reporting codes from the provider’s documentation of an encounter; but sometimes, like when a patient has a chronic condition but comes in for a different reason, it can be tricky to tell whether the condition should be reported as well.

Ideally, the provider’s documentation clearly states whether and how they considered the patient’s other conditions during their assessment and management/treatment of their current complaint. Educating providers on the importance of this kind of specific documentation is a huge boon to medical record accuracy and makes coders’ jobs easier, as the documentation may show explicit reasoning to report other conditions.

However, sometimes documentation may not be enough, because ICD-10-CM coding involves great specificity and guidance is often generalized and frequently evolving. For example, several AHA Coding Clinic^® questions have addressed when coders should report additional diagnoses, and it’s still sometimes difficult to understand when doing so is appropriate.

In these moments, Randolph points coders back to the ICD-10-CM code books and invites coders to dive deep.

Look Closely at Code Notes for Guidance on Reporting Additional Dx

Figuring out whether you can report a condition beyond the primary diagnosis — especially when AHA Coding Clinic^® 3^rd Quarter 2021, Page 32, clarified that coders shouldn’t “assign codes based solely on diagnoses noted in the history, problem list and/or medication list” — means going back to the ICD-10-CM code book, like AAPC’s ICD-10-CM Expert: Diagnosis Codes for Providers & Facilities 2026.

“Look at your instructional notes. So, if we have any instructional notes out here that say code first or use additional code, we feel that it’s appropriate to pull from there also,” he said.

For example, if a patient has chronic kidney disease (CKD) and hypertension is mentioned only in the past medical history, the ICD-10-CM guidelines tell you to report those conditions, so you can pull that information in, he said.

“If it’s part of an etiology or a manifestation convention — the ‘Use additional code’ at the etiology code and the ‘Code first’ note of the manifestation code — [the guidelines] are out there stating you can code those,” he said, with the caveat that Coding Clinic^® may release different guidance in the future.

Randolph explained that some conditions have a specific Alphabetic Index entry structure where two conditions are listed together, with the etiology code listed first, followed by the manifestation code in brackets. In these situations, the code listed in brackets is always sequenced second.

He gave the example of dementia with Parkinson’s disease without behavioral disturbance, which appears in the Alphabetic Index like this:

“Dementia (degenerative (primary)) (persisting) (unspecified severity) (without behavioral disturbance, psychotic disturbance, mood disturbance, and anxiety) F03.90

“-with

“--Parkinson’s disease -see also Dementia, in, diseases specified elsewhere G20.A1 [F02.80]”

In this example, he explained that Parkinson’s disease (G20.A1) is the etiology, and the dementia (F02.80) is the manifestation. So, you’d code this condition with G20.A1 (Parkinson’s disease) as the primary diagnosis and report F02.80 (Dementia in other diseases classified elsewhere, unspecified severity, without behavioral disturbance, psychotic disturbance, mood disturbance, and anxiety) as well.

Look to Chapter Beginnings for Expanded Advice

Remember to look at the Chapter-Specific Coding Guidelines, not just the notes available with the codes themselves, because you may find expanded sequencing direction.

“You do have to watch in that section, sometimes, where that information is listed. So, you know, sometimes it’s under the individual code. You can see that sometimes it’s going to be the chapter-specific part that’ll give you that. So, you do have to pay attention to your code book to see when you can or when you can’t code those,” he said.

Going back to the hypertension example, when you’re looking at codes for hypertension, hypertensive heart disease, or heart failure, relevant information to the condition may not be part of the etiology/manifestation convention and therefore may not be listed with the codes. However, at the beginning of Chapter 9: Diseases of the Circulatory System (I00-I99), you’ll find expanded, relevant guidance.

“This is where, if you go down to the individual code level, you’ll see some instructional notes. But if you go all the way to the beginning of the chapter, you’re going to see the ‘Use additional code’ to identify the exposure to environmental tobacco, smoke, history of tobacco, dependence, the occupational exposure or environmental tobacco smoke, and then the tobacco dependence. So, make sure you are watching those, to be able to pull that condition in. If you do have a condition that would fall under hypertension, you’re always going to code that smoking information,” he explained.

Check back next month for more tips on how to navigate guidance when reporting additional diagnoses in the outpatient setting.

Rachel Dorrell, MA, MS, CPC-A, CPPM, Production Editor, AAPC