I'm sorry, i just saw this, my prayers for Marley too, do you think you should get a 2nd opinion on treatment? is that an option for you? I mean do you have a good relationship with your vet or do you feel comfortable searching for a specialist in cats in your area? you could do a search for vets that service cats only and maybe get a better diagnostic workup and prognosis before things worsen. Or is your vet really thorough and all. there is no fip specific test out yet. The newest thing is "footprinting" but it is only a few labs across the country that are capable of doing it- maybe your vet is able? I am so sorry. Again, I will pray for Marley to recover.