Just read your other thread...
How long has Ping been not himself? Since he had the booster vaccine? Sorry if I've missed you saying how long, but just wondering.
If they're doing a general health blood profile, that should show up any of the usual older cat problems (liver/kidneys etc), but a starved blood test sounds like they're testing for other things, as pre-anaesthetic and general health profile bloods don't require starvation.
Let us know what the blood results are (unless they're sending them off to the lab)
Hope Ping picks up...
Liz x