If a 240 lb well muscled male drank 12 beers, was tested 72hours later who drank lots of fluids and was tested at the following levels what are chances of positive results?
ETG level 500

With the information provided I would predict both EtG (cut off 500) and EtS (cut off 100) would be negative at 72 hours. Please note that all studies to date have found wide variation between individuals for clearance time of EtG and EtS.

One of the more recent studies was published in Alcohol and Alcoholism October 2009 and can be found here. (http://alcalc.oxfordjournals.org/cgi/reprint/44/1/55)