Richard - yes, sorry, I did distract from your guesstimate for 'a' test.
PRM's markers are validated for the purposes of obtaining a patent. It is quite possible that the method described in that patent may not provide sufficiently specific test results. (Are these lung cancer patents available to read?? I agree that my reading them would make a material difference to my concerns!)
ie. many other poor tests probably have patents and are 'fully validated', but are not worth commercialising.