amyotrophic lateral sclerosis &

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

[erinraye517]

My dad has ALS so I've read up on a few things.  It sounds like ALS to me.  It's very fast moving.  My dad was diagnosed in 2007 and is in the end of the middle stage now.  His has been progressing fairly slowly.  I do know that throughout his diagnosis, we were told that the only way to diagnose ALS is to rule out everything else. There is no difinative test for ALS since they don't know what triggers is.  The only thing that can be tested for is if it is FALS or Familiar ALS which is genetic.  My dad has non-genetic.  They believe that he was exposed to chemicals in Vietnam which have caused this mutation.