DRG Logic

On this page, you can browse and explore DRG groups and grouping rules that lead to them. You can choose to display DRGs by MDC groups or as a single list in grouping logic order.

How the DRG Logic page works:

1. First select the MDC from the left selection tree and click the arrow button (>) to open the DRGs belonging to the MDC. Note that the DRGs are in the order of their appearance in the logic table which may be different from the order defined by DRG number.
2. Then, select the DRG under the selected MDC. One or more rules that may lead to this DRG open to the right. Alternatively you can search DRG with search function above MDC tree. Enter a DRG code or part of DRG name. Tree is filtered by the entered text.
3. Rule details are displayed on the right side of the page. You can print rule details of the shown rule by clicking Print button. If that rule has been used to group a case that is open on the DRG grouping page, the DRG grouping information that matches to the rule is also displayed.
4. If there is more than one rule associated with this DRG then you can move between the rules by using << 1 2 3 ... >> buttons on the bottom right.
5. Click the links on the rule details in order to see listing of all the diagnosis or procedures that have the specified property or belong to the specified category.

You can switch between MDC tree view and linear list view using Group by MDC selector. You can print out the selected rule or copy it to clipboard using the buttons in the top-right corner of the page.

The following fields are used to define the DRG grouping:

Note that the conditions for one DRG are necessary but not sufficient for the case to fall into the group in question. The grouper examines the DRG logic table in top-down order, and the first row that matches the given values ​​determines the DRG. Thus, the condition is also that the conditions of any previous line are not met.

Properties and categories window

You can activate this window by clicking links of the properties and categories on the rule details in the DRG logic page. All the diagnosis or procedures that have the specified property or that belong to the specified category are retrieved and listed. If you click on the “Operating room procedure” and the selection criterion is “must be” then all the operating room procedures are retrieved. If the criterion is “must not be” then all the procedures that are not operating room procedures are retrieved.

At the top of the window you can see selection criteria and value which is searched for, for example procedures that have procedure property “Pacemaker (cable) implant or replacement.” In addition, the list of diagnoses and procedures can be filtered based on the code and/or the description. As a search phrase you can use full words or parts of a word. When you find the appropriate code, click the row to transfer the code to the DRG Grouping page.

Listing all DRG rules w/o MDC tree

If you need to see full DRG rules listing in order of logic definitions then uncheck Group by MDC. In this view rules are listed in a linear list w/o MDC upper level grouping. This is the technically more correct way of looking at the rules in some cases. Number in square brackets after DRG name is the rules ordering number in the order grouper scans the rules.

About NordDRG grouping rules interpretation

NordDRG grouping rules are interpreted, roughly speaking, as follows. For further details please refer to the NordDRG manual by the Nordic Casemix Center.

1. NordDRG is determined based on diagnosis, procedures, age, sex and discharge code. Diagnosis codes and procedure codes are not used directly but indirectly by using diagnosis’ categories, diagnosis’ properties and procedures’ properties.
2. Pre-MDC groups are matched first. If there is no match then the actual MDCs are examined by first determining the actual MDC based on the principal diagnosis and then branching to the right MDC in the decision logic tree. If there are no matches in the actual MDCs then post-MDC rules are examined.
3. The first match determines the DRG. The order of rules in the logic definition table differs from the order of DRG numbers. Where there are rules for several variables (such as for diagnosis category and diagnosis properties) then all the rules must match. Diagnosis category is determined based on principal diagnosis only.
4. A minus sign (-) before a property or category means that the property or category must not match.
5. There are three possible values for OR-property: 1=OR-room procedure, 2=Procedure that is significant in ambulatory care of patients and 3=Procedure that can be performed in casual settings. The last code indicates that the procedure does not affect DRG assignment in the absence of other procedures with either OR=1 or OR=2. Independently of this property the procedure may still have procedure properties and even procedures in 0 groups may therefore affect the assignment. In the logic table this is reflected in the OR-variable that now needs to have 4 defined levels: S = Surgery - The patient has to have at least one procedure with OR=1, N = Non-surgical inpatient - The patient may have one or more procedures with OR=2 but none with OR=1, P = Ambulatory procedure patient - The patient has to have at least one procedure with OR=2 or OR=1, Z = Conservative outpatient - The patient may not have any procedures with OR=1 or OR=2. Empty means as always that the value of OR is not tested.
6. In sex, age and complicated fields if there is no value then these variables are totally ignored.
7. Secondary procedure property: The procedure properties are equal to the procedures properties. In addition to that a special rule applies: if there is a plus sign (+) in this field then the patient must have a secondary procedure. In practice the requirement is that patient has at least two operating room procedures. If there is a minus sign (-) in this field then the patient must not have more than one operating room procedure. If secondary procedure property and the first procedure property contain the same property then the patient must have two procedures, which contain the specified property.
8. A case is complicated, if at least one diagnosis or procedure code indicates complication. However, this diagnosis code may not be the principal diagnosis. There are also exceptions for this rule: Every complicating diagnosis has an exclusion list, and if the principal diagnosis is a member of the list, the case is not complicated. Some diagnosis codes do not complicate the case by themselves; they need another specified diagnosis code to complicate. Again, this diagnosis may not be the principal diagnosis. It’s very important to note that when browsing the DRG rules database the rules are interpreted in the order of their appearance. Thus, it’s not just enough to examine one particular DRG but keep also in mind that in order to enter in this DRG the input data should not have lead to any previous DRG in the order they are listed in the rules database.
9. Note that for diagnosis properties, specifically second diagnosis properties (ch K in the middle) are checked agains the 2nd diagnosis only.

Note that MDC plays two slightly different roles in NordDRG.

• On the other hand, MDC is an intermediate level variable used internally in DRG reasoning logic, which is inferred from the main dg. There may be MDC groups in this role that, however, are not present as a recoverable MDC group as a result of DRG grouping.
• On the other hand, MDC is the upper hierarchical level of the final DRG grouping result for reporting, derived from DRG for output.

Example:

• MDC 30 appears in DRG 259A as a required condition in the DRG Grouping Rules section: the main diagnosis must belong to this MDC group.
• However, the MDC group of the 259A DRG is 9.

Second diagnosis property (Finnish DRG versions only)

Starting from 2023 Finnish versions NordDRG system uses the second diagnosis in a specific way. Before that, only 1st (primary) diagnosis has had a special meaning and all the other diagnosis could have been in any order, so that this secondary diagnosis ordering doesn’t affect grouping results. Now, logic includes specific features that are checked against the 2nd diagnosis (the 1st secondary diagnosis, ie. DG2A and DG2D in input). If encounter is follow-up or after-care visit, then this (particular Z codes) must be given as the primary diagnosis or reason for visit. In this case, the 2nd diagnosis must indicate the primary cause, illness or condition for what this follow-up or check is needed. Possible other diagnosis are then marked in the dg positions DG3 and after it.