Github pull request rebuilding

We are building as per the teamcity blog to build refs/pulls however github advise this is not a recommend approach.

The reason is that a closed pull request can have these refs left behind.
Their recommendation is to check the pull request state and only build if the request is open.

Before I start coding this into a powershell script and having to worry about rest API authentication, is there anyway built into teamcity to only build open github pulls?
Or a special github pull request VCS root?

Thanks

Chris