** Shares of cancer diagnostic test maker Grail GRAL.O fall 18.8% to $34.81 in extended trading
** Company's Q1 revenue of $31.8 million misses analysts' average expectation of $35.2 million, according to data compiled by LSEG
** GRAL reports quarterly loss of $3.10/shr, vs analysts' average estimate of $4.09/shr
** Up to last close, stock up more than double YTD
(Reporting by Christy Santhosh)
((Christy.Santhosh@thomsonreuters.com))