diagnostic assay

NOUN
16 LETTERS · STARTS WITH D

diagnostic assay is a valid 16-letter word worth 22 points in Scrabble and 24 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
D2I1A1G2N1O1S1T1I1C3A1S1S1A1Y4
2 + 1 + 1 + 2 + 1 + 1 + 1 + 1 + 1 + 3 + 0 + 1 + 1 + 1 + 1 + 4 =22 PTS
DOUBLE WORD → 44TRIPLE WORD → 66
MEANING

What does diagnostic assay mean?