Hi!
Before turning that it into a redirect, it might be worth looking atthe content. There seems to be some discrepancy between the results from http://wdqs-beta.wmflabs.org/ and those from http://query.wikidata.org. When submitted to both endpoints the following query returns different results:
These are fed from the same data and supposed to be the same code, so I wonder how it happened there's a difference... The query actually shows there's two values for Q181391 on P699 - 987 and DOID:987.
I'll investigate that. It may be some kind of bug. Thanks for bringing it to my attention.