Clinical decision support rules play a key role in the overall delivery of CDS. CDS rules typically follow a common pattern, which has been modeled in several healthcare standards formalisms. The Event-Condition-Action
model, as used in the HL7 community, is described below.
A CDS event is the clinical situation in which a decision support rule will be applied. First something must happen before the rule can be utilized. Examples of CDS events include:
A CDS condition defines the question(s) that must be answered to determine the outcome of the rule. Examples of conditions include:
The CDS action describes what should be doneif the condition evaluates to true. Examples of actions include:
An informal representation or rule template which captures the Event-Condition-Action pattern is shown below. This pattern can be read as "ON event IF condition THEN action".
Figure 3.1-1: Event-Condition-Action rule template
Rules may reference both EHR data and reference data such as terminology to determine whether or not a specific condition is true. This topic will be explored in more detail in section 4. Inference Engine.