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Extensions & Clustering – Two New Features within ICD-11 [PODCAST]

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The Hospital Finance Podcast

In this episode, we welcome back Bridget Nolan, Coding Analyst at BESLER, to talk about the two new features within ICD-11.

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Highlights of this episode include:

  • Need for 11th revision of ICD
  • ICD-11
  • Extension Codes
  • Clustering

Mike Passanante: Hi, this is Mike Passanante and welcome back to the award-winning Hospital Finance podcast. Here to talk about extensions and clustering to new features in ICD-11 is Bridget Nolin, a coding analyst on the Revenue Integrity Services team here at BESLER. Bridget is a highly skilled coding analyst with 20 years experience in ICD-10-CM PCS coding, MS-DRG validation, inpatient coding audits and education, and CDI reviews. She holds a Master’s in Health Information Technology and a Bachelor’s in Health Information Administration. Bridget is credentialed by AHIMA as a Registered Health Information Administrator, Certified Coding Specialist, and an AHIMA approved ICD-10-CM PCS trainer. Bridget, welcome back to the show.

Bridget Nolan: Hi, Mike. It’s very nice to be back.

Mike: So we’re talking about ICD-11. So can you first give us some background on the need for an 11th revision of ICD?

Bridget: Yes. After almost 30 years since the creation of ICD-10, it is easy to understand the need for an update. There are a few reasons that this revision was necessary. With major advancements in medicine and science, it was clear that ICD-10 could not accommodate the changes necessary from a classification or from a clinical standpoint. So ICD-10 in its current format could not sustain the changes necessary to support the advances we have seen over the last two to three decades. And there were some chapters that needed structural changes. Also, there is a need to capture more information, especially for morbidity cases. And then finally, the need to work within an electronic environment is ever increasing. The current high tech world requires ease for things like data exchange, maintenance and development that aid in the translation and modifications of the system. In 2007, the World Health Organization, WHO, started work on ICD-11. And now here we are in 2022, with implementation likely in the very near future.

Mike: Okay. Thanks for that background, Bridget. Bridget, what is new in the world of ICD-11?

Bridget: All right, so this 11th version of ICD is a greatly different version than that of the ICD-10 clinical modified version we currently use here in the US. That begins with a new name, ICD-11-MMS. MMS stands for Mortality and Morbidity statistics. There has been a major redesign of the classification to be more IT friendly and to support better data collection on morbidity. This will allow for ICD-10 to link to other terminology classifications, to support EHRs and health information systems, and help with consistency and interoperability across different uses. So for the first time, ICD is fully electronic, currently providing access to 17,000 diagnostic categories with over 100,000 medical diagnostic index terms. But for today, we’re going to focus on two major features of ICD-11, extensions and clustering.

Mike: All right, Bridget, let’s jump right in. What can you tell us about extensions and clustering?

Bridget: Okay, so first let’s talk about extensions or some may refer to as adjunct codes. ICD-11 has an addendum Chapter X called Extension Codes. This chapter contains numerous codes, each starting with an X and containing information on concepts including disease stage, severity, histopathological, [inaudible], and anatomical details. When the extension codes are linked to a stem code representing a clinical state or disease, the extension codes add significant detail and allow for multidimensional coding. Now, this approach produces longer code strings but substantially reduces the total number of stem codes needed in other ICD-11 chapters. Stem codes can stand alone, whereas extension codes cannot. Extension codes will always follow a stem code and may not occupy the first position in a code cluster. There are two types of extension codes. Type one extension codes adds detail onto a stem code entity or disease coded from chapter 11, 1 through 26. An example could be severity – whether it’s mild or severe – ecology, the infection agent – what is it – the anatomical detail – left, right, or a specific quadrant – and acuity. Is it acute or is it chronic? Type two extension codes qualify a diagnosis and can be applied to codes from any chapter. Diagnosis qualification means an additional detailed description of a coded disease, and this is a new feature of ICD-11. An example would be main condition. Is this the principal condition or secondary condition? What is the POA – was it present on admission – and the certainty of a diagnosis? Is it definitely confirmed or is it a possible probable?

Mike: Okay, so now let’s talk about clustering.

Bridget: So a diagnostic statement is created when individual parts of the diagnosis are linked together. The use of ICD-11 is simple and flexible due to these individual parts. Clustering is how ICD-11 links together the diagnosis parts to create a diagnostic statement. Special characters like ampersand or the forward slash are used to link the diagnosis codes. So some examples of cluster coding would be stem plus stem joined by a forward slash. For example, if you have Type I Diabetes with CKD – chronic kidney disease – stage five, the code for each would be linked together by a forward slash. 5A10/GB-61.5. The second example would be a stem plus an extension joined with an ampersand. So that would be something like, unspecified asthma with status [inaudible] severe. So you would have CA-23.31, ampersand, XS25, and this is all joined together as one code.

Finally, you could have a mixed cluster using both the ampersand and the forward slash. For example, Type I Diabetes Mellitus with chronic kidney disease, CKD, stage five, but also with the added note that it was POA – present on admission – and that would be the same as the beginning code. However, at the very end you would add ampersand XY6M to notify that the condition was present on admission. This use of cluster coding is also referred to in ICD-11 as post coordination. Post coordination allows for increased specificity and detail without having to create additional codes. I think these two features will only enhance the ease of use when using ICD-11.

Mike: All right, Bridget, and I’m sure this isn’t the last time we’re going to be talking about ICD-11 over coming months. But at this point, do you have any final thoughts you’d like to share on ICD-11?

Bridget: Absolutely. So anyone who is wondering why are we even looking at this right now? So I understand. I really do. But remember, the US only implemented ICD-10-CM for use about seven years ago, whose ICD-10 is 25 years old. While an implementation date for ICD-11 in the US is still unknown, operations, coordination, and education are needed for smooth transition. This is the time to be proactive in our anticipation of a full implementation of ICD-11. So if you’re interested in knowing more about ICD-11, you can always google ICD-11. Get lots of information there. You can visit the WHO website at And the WHO website provides a bunch of information. There is a coding tool, there is implementation– there’s an implementation or transition guide and there is also ICD-11 training modules. There’s also great information specifically aimed at coding professionals on the AHIMA and the AAP website.

Mike: Excellent. We’ll be sure to include those links on our blog for that information. Bridget Nolan, thanks so much for coming by today and giving us the first glimpse of ICD-11.

Bridget: Absolutely. Thank you, Mike, for having me.

[music] This concludes today’s episode of the Hospital Finance Podcast. For show notes and additional resources to help you protect and enhance revenue at your hospital, visit The Hospital Finance Podcast is a production of BESLER, SMART ABOUT REVENUE, TENACIOUS ABOUT RESULTS.


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