Refinement of the Medicare diagnosis-related groups to incorporate a measure of severity - Medicare Payment Systems: Moving Toward the Future

Health Care Financing Review, Winter, 1994 by Nancy Edwards, Dorothy Honemann, Dana Burley, Maria Navarro

Medical/Surgical

The resource use for surgical cases was initially evaluated separately from medical cases. There were instances where the subclass numerical values for a secondary diagnosis present in surgical cases ranked higher than when present in medical cases, although the reverse was true in a comparable number of circumstances. The subclass values for these two types of cases indicated that the resource use for a particular secondary diagnosis did not vary consistently between surgical and medical cases. Therefore, a secondary diagnosis is uniformly categorized as a non-CC, CC, or MCC, regardless of medical/surgical status.

The secondary diagnosis data were evaluated to determine if there was a difference in resource use between cases in which the patient was discharged alive or died during the hospital stay. For most secondary diagnoses, the charges were similar for the two groups. There were, however, a few diagnoses where the difference in charges and clinical considerations supported, a different CC designation for patients who died before discharge. For these diagnoses, the patients who were discharged alive required significantly more hospital resources than the patients who died. That is, the resource use (as indicated by the subclass values) for the live patients approximated the expected value for the MCC class. The subclass values for the cases in which the patient died approximated the expected value for the CC subclass. Therefore, each of the diagnoses is designated as an MCC in cases where the patient is discharged alive and as a CC in cases where the patient died. These are listed in Table 4.

Table 4
Diagnoses With Differential
Live/Dead Classifications
Code               Description
427.41          Ventricular Fibrillation
427.5           Cardiac Arrest
785.51          Cardiogenic Shock
785.59          Other Shock Without Mention of Trauma
799.1           Respiratory Arrest
998.0           Postoperative Shock
SOURCE: Health Care Financing Administration, Bureau of Policy
Development, 1994.

Secondary Diagnoses Currently Required for DRG Assignment

Special attention was paid to specific secondary diagnoses that are necessary to determine DRG assignment. For example, specific secondary diagnoses are required to assign a case to the DRGs for acute myocardial infarction (DRGs 121-123), multiple trauma cases (DRGs 484-487), and HIV cases (DRGs 488-490). For each of these specified secondary diagnoses, we compared the cases assigned to these DRGs with cases having the same secondary diagnosis but assigned to other DRGs. Our analysis indicated that the pattern of resource utilization incurred by these secondary diagnoses was similar to all other secondary diagnoses.

Because these secondary diagnoses are required to determine assignment to certain DRGs, they should not be used to determine assignment to either a CC or an MCC subclass for these DRGs. Our rationale is similar to that used in determining the CC exclusions, which preclude a secondary diagnosis from being treated as a CC in cases in which it is closely related to the principal diagnosis. For example, a secondary diagnosis of Congestive Heart Failure (diagnosis code 428.0) was excluded from subclass determination for DRGs 121 (Circulatory Disorders With Acute Myocardial Infarction and Cardiovascular Complications Discharged Alive) and 124 (Circulatory Disorders Except Acute Myocardial Infarction With Cardiac Catheterization and Complex Diagnosis).