Unfortunately, I'm not in a position to comment on how things are done in Spain or in Portugal. During the course of our discussions last spring with Canadian Blood Services, we were told that Italy had adopted a system where the focus was on people's sexual behaviour, not on their sexual orientation.
Therefore, as my colleague said, setting up a registry where people would be asked to answer questions about whether or not they had engaged in risky or unprotected sex would be an effective approach, rather than targeting one group in particular.