The Blood Centre at HSA is something like ur central bank, a central repositary for blood for hospitals.
Blood donations at hospitals I believe are specific to ppl. U muz state name, IC number and so on. However, if ur blood is not suitable for the receiptent, it would not be given to him anyway but used by other ppl. There ain't no such thing as, "Oh, my friend is in SGH and den I go TTSH to donate blood to him."
If u have the heart to help, go all the way. Dun do things halfway.
I stand corrected on my information abt paitent-specific blood donation.