Yes, DIASTASES is a Scrabble word!

Letter values in Scrabble US: D 2, I 1, A 1, S 1, T 1, A 1, S 1, E 1, S 1.

Is it a valid word?

DIASTASES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

separation of an epiphysis from the long bone to which it is normally attached without fracture of the bone

Not playable in Scrabble US: DIASTASIS.