The AlphaTrak will always give higher numbers than the Relion because it's a pet meter....the Relion is a human meter
You really can't compare the numbers exactly...the only "official" number we have is that 68 on the AlphaTrak is the same as a 50 on a human meter....after that, the numbers really don't compare
The reason most of us use the Relion is because of the cost (and availability) of the AlphaTrak strips...they cost about $1 EACH, and if you run out at 3am on a Sunday morning and your cat is in hypo territory, there's no place to get more
A very general rule is that the AT runs about 35% higher than a human meter....but that's VERY general (although it works pretty good with your example...330 + 35% is 445 which is really close to the 425 you got)
Also, ALL meters are allowed to have a 20% variance by the FDA....that means that even if you use the same meter on the same drop of blood, the number can vary plus or minus 20%
The protocols written here are all done with human meters. What we watch for more than exact numbers are "trends"...is the current dose getting the cat where we want them?