ICD-10 data meets the IPPS Rule: MS-DRG proposed change highlights, part 1

June 17, 2019 / By Rhonda Butler

If there is a theme to this year’s proposed MS-DRG changes in the IPPS proposed rule, it is “ICD-10 Data.” Now that two years’ worth of ICD-10 coded MedPAR data is available for analysis, CMS is using it to inform their proposed changes to the MS-DRGs. This year’s changes include a fresh look at the ICD-10-CM codes on the MCC and CC lists, a review of the “Unrelated OR DRGs” 981-983 and 987-989, and surgical DRG modifications that use the structure of ICD-10-PCS instead of DRG assignment inherited from the ICD-9 version of the MS-DRGs.

Changes to MCC and CC designation

The last time CMS conducted a comprehensive review of the MCC and CC severity level designation was twelve years ago, when CMS transitioned from DRGs to MS-DRGs for FY 2008. Given the transition to ICD-10-CM and the significant changes to diagnosis codes, CMS said, it was time to do the analysis again. The analysis consists of a simulation that takes all ICD-10-CM diagnosis codes assigned as secondary diagnoses in the MedPAR claims data and assigns each code a “C” value. The C value places each ICD-10-CM code on a number line somewhere between 0 and 4. The value indicates whether its current MCC, CC, or non-CC designation is appropriate—and if not, whether the code should be moved from the CC to the MCC list, moved from the MCC to CC list, or should not have a severity level designation at all. CMS’ clinical advisors use the results of the simulation combined with their clinical judgment to decide to what degree a particular secondary diagnosis is likely to impact resource use and recommend changes accordingly.

The results of the recommended changes for FY 2020 are summarized in the proposed rule, and each proposed change is listed in a separate Excel file.

If the proposed changes from this year’s comprehensive review go into effect, the number of codes designated MCC will decrease from 3,244 codes to 3,099 codes, and the number of codes designated CC will decrease from 14,528 codes to 13,691 codes. By applying the proposed changes to the FY 2018 MedPAR data, CMS estimates the overall percentage of cases with one or more CC/MCC present on the record would decrease by about five percent, from the current level of 81.5 of all records containing at least one CC or MCC, to 76.6 percent. Below are a few examples of proposed changes:

• More than half of the codes on the list of proposed changes are from the Neoplasm chapter, and CMS proposed to change their severity level designation from CC to non-CC. The reason given is that the simulation showed that taken as a group, the neoplasm codes when listed as a secondary diagnosis were not likely to significantly impact resource use. The proposal goes on to explain that since the neoplasm is not the reason for admission (not listed as the principal diagnosis), it makes clinical sense that it does not significantly impact resource use for that hospital stay.

• 150 ICD-10-CM pressure ulcer codes specified as stage 3 or stage 4 are proposed for severity level change from MCC to CC. CMS explained that the resource use appears to be largely consistent with a CC level, regardless of the stage of the ulcer, because the underlying illness or debility of the patient that predisposes the person to pressure ulcer is the primary driver of resource use, and further, the presence of any pressure ulcer is a more important indication of resource use than the stage of the ulcer.

• CMS proposed changing the severity level designation from MCC to CC for several codes specifying acute myocardial infarction (MI) in categories I21 and I22.

Review of “Unrelated OR DRG” assignments

CMS annually reviews what are informally called the “unrelated OR DRGs” (MS-DRGs 981-983 and 987-989) to look for combinations of diagnosis and procedure codes that are likely to be related, and therefore the procedure code triggering the unrelated DRG assignment can be assigned to a related surgical MS-DRG—a surgical DRG in the MDC where the diagnosis is found. This year, with the benefit of ICD-10 coded data, CMS was able to uncover some interesting combinations and propose solutions:

• Principal diagnosis of Gastrointestinal Stromal Tumor (GIST) paired with a procedure code for open excision of stomach—This code combination triggers the unrelated OR DRG because the diagnosis is currently assigned to MDC 8 (diseases of the musculoskeletal system and connective tissue). GIST neoplasms are currently assigned to the musculoskeletal MDC because stromal tumors are classified in ICD-10-CM as connective tissue neoplasms. CMS proposes to resolve the issue by moving the diagnosis codes to MDC 6 (diseases of the digestive system) where they are more clinically at home, and so future claims containing this principal diagnosis and a digestive system procedure will no longer trigger an unrelated OR DRG.

• Principal diagnosis of pressure ulcers stage 3 and 4 paired with procedure codes for excision of bone—Procedures describing open excision of the sacrum, coccyx, and pelvic bones were assigned to an unrelated OR DRG when paired with a principal diagnosis of pressure ulcer, because pressure ulcer codes are assigned to MDC 9 (diseases of the skin, subcutaneous tissue, and breast). Since the procedure codes are used to capture debridement of a pressure ulcer that extends down to bone, these procedures are related to the principal diagnosis. CMS proposes to assign the procedure codes to a surgical in MDC 9, MS-DRGs 579-581 Other Skin, Subcutaneous Tissue and Breast Procedures with MCC, with CC, and without CC/MCC respectively.

My next blog will highlight a few other proposed changes I found interesting, involving ECMO procedure codes, the combination diagnosis code for pulmonary embolism with acute cor pulmonale and a re-vamp of the MS-DRGs for transcatheter cardiac procedures.

Rhonda Butler is a clinical research manager with 3M Health Information Systems.