Hi Umar,
You should declare the variable in your process
In your bpmn file will look like this:
<itemDefinition id="_doctorsDecisionItem" structureRef="String" />
...
<process...>
<property id="doctorsDecision" itemSubjectRef="_cvItem"/>
No matter if it is "external" or not.
In your script node you can use
System.out.println(kcontext.getVariable("doctorsDecision"));
Demian