** Medical diagnostics co Guardant Health GH.O shares rise 2% to $112.35 premarket
** Co reports preliminary Q4 revenue of $280 mln vs analysts' average estimate of $268 mln, according to data compiled by LSEG
** Attributes performance to year-on-year surge in oncology testing volumes by 38%
** Co also attributes performance to wider adoption of its Smart Liquid Biopsy platform
** Volumes for co's blood-based cancer screening test, Shield, increase nearly six times
** GH stock more than tripled over past year
(Reporting by Utkarsh Tushar Hathi)
((utkarshtushar.hathi@thomsonreuters.com))