scrum - When to mark a work item blocked versus creating an impediment work item in TFS2013 -

our team going start tracking our roadblocks (or impediments) better see there impediment work items , there blocked dropdown in task. when set task blocked vs creating new impediment work item?

my take on is, microsoft expect use impediment item of work purely unblocking problem:

from msdn:

by defining , managing impediment work items, team can identify , track problems prevent completing tasks efficiently. teams typically identify impediments during daily scrums. scrum master responsible helping resolve these impediments , improve team productivity.

for example:

• "alice needs copy of vs 2015 rc next spike, won't let install it", tracked via impediment.
• "bob needs task code reviewed carol, she's on leave today" done blocking task.

this take on ms plan these used on. experience, pick works team, adjusting in retrospective necessary. try using 1 or other. long work done, blockers unblocked , team happy, doesn't matter.