To be honest, I'm a dexcom G6 user and had to google to find out what an MDA card is.
I've just been going through the standard screening archway and it hasn't caused me any issues.
But I suspect strongly that the xray machine fries a dexcom transmitter so if you can have documentation (I got a print out from dexcom) that discourages them from xraying a spare then that is good.
Edited to add Welcome to the forums
@SharronCE