ICD-10 MS-DRG shifts, Part 3 – Top DRGs

November 19th, 2012 / By Ron Mills, PhD

We talked earlier about the CC/MCC shifts that affect nearly all DRGs. Now we’ll change our point of view to the DRGs themselves and rank them by their shiftiness. That can be tricky, since there are several ways to measure shifting. If you take the percentage of cases whose DRG changes to something else, DRG 215, Other heart assist system implant, comes on top with 47% of its cases going into some other DRG, but 215 is rare (only 118 cases in our sample of 10 million).

So I’m going to use the DRG’s net weight change to rank them. When a case in DRG A under ICD-9 goes to DRG B under ICD-10 (which, I remind you, only happens about 1% of the time), we look at the difference between B’s weight and A’s weight. For about 60% of these cases, this difference is negative (less money for this case when coded in ICD-10) and for 40% it is positive (more money when coded in ICD-10). That 60/40 split is across all DRGs, but for any given DRG, it may be overwhelmingly one way or the other. So we add up all the differences for DRG A and call it DRG A’s net weight change. This number tells you how much less (or more) you can expect to be paid for all your cases now in DRG A if they were coded in ICD-10. It neatly ties together the frequency of the DRG, its shiftiness, and its financial impact.

1.  MS-DRG 812, Red blood cell disorders w/o MCC.

Positive, about 2.25 cents per $100 of DRG 812 reimbursement. Yes, the top guy is in your favor, imagine that. It comes about from a guideline change. I quote from the ICD-10-CM Guidelines chapter 2.I.4, p.29:

When the admission/encounter is for management of an anemia associated with [a] malignancy, and the treatment is only for anemia, the appropriate code for the malignancy is sequenced as the principal or first-listed diagnosis followed by code D63.0, Anemia in neoplastic disease.

In ICD-9, most of these records had the anemia as principal diagnosis, and hence went into DRG 812. Under ICD-10, the malignancy has to be coded first, which shifts these cases into generally higher paying cancer DRGs.

2.  MS-DRG 981, Extensive O.R. procedure unrelated to principal diagnosis w/MCC.

Negative, a little under one penny per $100 of DRG 981 reimbursement. A case lands in this DRG when the grouper is unable to match up the diagnoses and the procedures on the record. It is easier for this to happen under ICD-9, with its non-specific procedure codes. Under ICD-10, with its greater specificity, the grouper is better able to associate procedures with principal diagnoses, so instead of being “unrelated,” the case goes into a surgical DRG in the principal diagnosis’ MDC. These usually have a lower weight than the catch-all “unrelated procedure” DRGs.

3.  MS-DRG 391, Esophagitis, gastroent & misc disgest disorders w/MCC.

Negative, about 1.8 cents per $100 of DRG 391 reimbursement. This shift is an example of the MCC shifting we talked about before. About 90% of the weight change is due to ICD-10-CM code K22.8 Other diseases of esophagus, which includes esophageal hemorrhage in its definition. Esophageal hemorrhage is a separate code, 530.82, in ICD-9, assigned to MS-DRG 368 in ICD-9. 530.89 Other disorders of esophagus is assigned to MS-DRG 391. Their frequency data is similar, so K22.8 takes the DRG attributes of the ICD-9 closest match 530.89, not an MCC.

4.  MS-DRG 885, Psychoses.

Negative, about one penny per $100 of DRG 885 reimbursement. Nearly all of these cases move to MS-DRG 881, Depressive neuroses. Under ICD-9 their principal diagnosis was 296.20, Major depression, unspecified. This becomes F32.9 in ICD-10, which includes Depression NOS (311 in ICD-9), so F32.9 cannot take the case to DRG 885. We talked about these codes in more detail in the previous blog in this series.

5.  MS-DRG 066, Intracranial hemorrhage or cerebral infarction w/o CC/MCC.

Positive, about 1.4 cents per $100 of DRG 066 reimbursement. ICD-10 secondary diagnosis I63.59,Cerebral infarction due to unspecified occlusion or stenosis of other cerebral artery, is coded when either 433.31 or 433.81 would be coded in ICD-9. While 433.31 is excluded as CC by the principal diagnoses leading to DRG 066, 433.81 is not. The closest matching translation for I63.59 is 433.81 , so I63.59 takes the DRG attributes of 433.81, which means it is not excluded. MS-DRG 066 cases with 433.31 on their ICD-9 record go to the higher paying MS-DRG 595 under ICD-10.

Next time I’ll do the next five, unless I get feedback indicating you’ve had enough.

Ron Mills is a Software Architect for the Clinical & Economic Research department of 3M Health Information Systems.