My father tested negitive for ALS & positive for PLS, but he has the ALS symptons. With PLS it takes 10+ years for symptons to take full affect. With ALS everything happens fast. My dads symptons happened overnight in late 2006, it's now 2009 & he is on his last leg. He was tested for ALS in march for the 3rd time and was still negitive for ALS. It's only been a little over 2 years since symptons started & he can't walk, talk, swollow, chew, or do pretty much anything on his own. Is it possible to get false negitive tests, even if tested multiple times? Should he be re-tested, because I heard PLS can turn into ALS? Not for sure though. Can I please have some awnsers because I would like to know if my dad has to fatal or un-fatal disease. Thank you