Add a new element to DetectedIssue called "documentationLevel".  This element would indicate the quality and quantity of the medical literature supporting the existence of the DetectedIssue (e.g. drug interaction).  This element would need a value set binding of documentation levels.  As an example, for Medi-Span (Wolters Kluwer), the possible values are {Established, Probable, Suspected, Possible, Doubtful/Unknown}.  The binding to the new value set should be something other than "required", since different systems may use different values.

The cardinality should be 0..1.