What CMS left undocumented in the Final Rule, part 1

I've been talking about MS-DRG since they were first unveiled back in April of this year. Since that time we have had lots of education and information about the MS-DRG system, but I’m amazed at how much about this new MS-DRG system remains clouded in mystery and intrigue amongst the majority of the industry. Because of this, I’m going to start a multiple part series talking about what is left undocumented in MS-DRGs. Over the next couple weeks I will blog on many of the issues within the MS-DRG grouping system that people in the industry still have misconceptions and misunderstandings about.

First off, let me say this: Do not use the CMS V24 to MS-DRG Crosswalk.  Wait, let me say it again: Do not use the CMS V24 to MS-DRG Crosswalk! Why do I say this? I say it because some of the crosswalk information is misleading at best, and downright incorrect in at least one situation. Over the next couple of weeks I hope to show you exactly what I mean.

Let’s dive in and start with one area that I feel is important, and it is the first one of these issues that I discovered. I talked about this at AHIMA a number of weeks ago and was amazed at the number of medical records coders who were unaware of the issue.

The images below represent the surgical hierarchy for MDC 9. For those who do not know, the surgical hierarchy is the order in which the grouper checks DRG criteria, looking for the first DRG where the claim group satisfies ALL the criteria to get into that DRG. For example, looking at the first image we can see that Plastic Procedures come before Perianal and Pilonidal Cyst Procedures. This means that if a claim has both a Plastic Procedure AND a Perianal/Pilonidal Cyst Procedure, it will group into the Plastic Procedure DRG because it comes first in the surgical hierarchy.

Looking at what CMS says in its crosswalk (see below), it seems as if all the cases from CMS-DRG 257 and 258 cross walk into MS-DRGs 582-583.

In looking at the third image, the first part of the new MDC 09 surgical hierarchy, we can see that MS-DRGs 579-581 (Other Skin, Subcutaneous Tissue and Breast Procedures) are above MS-DRGs 582-583 (Total Mastectomies for PDX Malignancy). MS-DRGs 579-581 are composed of V24 DRGs 267 Perianal/Pilonidal Procedures, 268 Plastic Procedures, 269/270 Other Skin, Subcutaneous Tissue and Breast Procedures. V24 DRGs 267, 268 are both higher in the surgical hierarchy than V24 DRGs 257-258 (Total Mastectomies for PDX Malignancy), BUT 269, 270 are LOWER in the surgical hierarchy than V24 DRGs 257-258.

This means that if a claim has both a Total Mastectomy with a PDX of Malignancy AND an Other Skin, Subcutaneous Tissue/Breast Procedure, then in V24 it would have been in the Total Mastectomy with a PDX of Malignancy DRG. However, under MS-DRGs it will be in the Other Skin, Subcutaneous Tissue & Breast Procedure DRGs. Nowhere in CMS’s crosswalk is this explained, and when people start coding claims there may be some unexpected results.

In particular, two procedures that are part of the procedure list for MS-DRG 579-581, 86.09 Skin and Subcutaneous Incision Not Elsewhere Classified and 86.3 Other Local Destruction of Skin, are now HIGHER in the surgical hierarchy than Breast Mastectomies for Malignancy. If we examine claims with only one of these two procedures(86.09, 86.3), we find that these cases have lower resource utilization (charges/costs and LOS) than the Breast Mastectomies for Malignancy cases.

Hopefully, CMS will address this issue in the future, but as of right now, it is undocumented by CMS in any MS-DRG documentation.