Salifert alk test kit

[dyereefer]

I have had my test kit for a while now over a year because I was in the planning stages of my new set up .I was wondering do these kits expire.
The reason I ask is when I do the test I get a reading of about 12DkH
but when I go to get it tested It comes back at off the scale ,when I use my even older aquarium pharm test kit it measures 16DkH.