124 CHAPTER 2.3 Table 5. Simplified decision table for START criterion C3; ‘Start acetylcholinesterase inhibitor for mild-moderate Alzheimer’s dementia or Lewy Body dementia’. 1 METADATA METADATA CONDITION CONDITION ACTION 2 ID Priority Episode exists Episode exists Medicine 3 value value icd10 icd10 atc 4 equals (=) equals (=) equals (=) equals (=) start if not present 5 Alzheimer’s dementia Lewy body dementia acetylcholinesterase inhibitor START C3 1 G30*, F00* N06DA* 2 G31.8 N06DA03 *The asterisk indicates that all subcategories starting with the letter/number combinations prior to the asterisk are included. The first five rows of each decision table are reserved for specifications about their components. Each component covers one column. The first row indicates what type of information the column describes: metadata about the criterion, a condition, or an action. The four subsequent rows contain information on the object acted upon, its attribute, the operator, and a user-readable comment. The remaining rows contain values that, together with the first five rows, form a proposition for the criterion. In Table 5, Lewy body dementia (text) is identified as an episode (Episode exists) being registered (equals (=)) with a specific ICD10-code (icd10), G31.8. A criterion can contain multiple rows of values, indicating that it can be inferred through several conjunctions. In such cases, rows are prioritized to indicate which inference rule takes precedence. In the given example, a different drug is prescribed for Lewy body dementia compared with Alzheimer’s dementia. As a result, Lewy body dementia is separately identified (in the inference rule with priority 2) and linked to the specific drug rivastigmine (N06DA03), and not the entire class acetylcholinesterase inhibitors (N06DA) as is the case for Alzheimer’s dementia. Note that the decision table format allows for some derivatives in notation to improve readability. Cells may be merged if their values are used in multiple prioritized inference rules. In Table 5, the criterion’s ID (START C3) serves both inference rule 1# and 2#. Explicit conditions do not have to be specified for medications that are to be started or stopped. In Table 5, the operator start if not present in the action column also acts as an implicit condition; acetylcholinesterase inhibitors should not yet have been prescribed to the patient. In Figure 3, the simplified START criterion C3 from Table 5 is shown as a flowchart. The priorities, conditions and actions in Table 5 are transformed into an algorithm, which follows the routes, choices and activities shown in Figure 3.
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