Why'd blood bank pick me for different donation types?

Factual Questions
1

I gave ordinary donations for years, then they started asking for double red cell donations (there’s a process to harvest them from my blood and return the depleted part of my blood back to me). I did one of these just yesterday. There were also a couple different times - once for platelets and once for plasma, if I remember right. How did they pick me to ask? I see a big crowd of people coming in for ordinary donations, then a few of us for these special ones. It doesn’t seem random – the last few donations, they’ve asked me for double reds. I’m curious how they choose whom to ask.

I have A positive blood, very boring as far as I know. Maybe because I’m a frequent donor anyway?

2

The hemoglobin requirement for a double red cell donation is higher, so not everyone has enough blood in their blood to do it, and presumably they know that you do because they test your blood from donations.

The process is also longer and a little less comfortable, so they probably try to get the lifers to do it rather than scaring away the newbies.

3

Their needs may change between appointments, and they may ask you to give whatever they’re low on.

The place where I give blood has you choose in advance what type of donation you’re going to make, and they only let you book whole blood donations online; the longer appointments have to be booked over the phone. I tried giving platelets recently and didn’t like it. They do the output and input all through one needle, which is kinda nice, but it took forever and I was uncomfortable the whole time it was in. I also got a little spinny from the calcium or whatever they add to the blood before they put it back in you. I salute those who can handle it, but I think I’m going to stick with whole blood donations.

ETA: And I’m O+; way more boring than you!

4

You kidding? You are exciting! You’re almost a universal donor! I think only O- would be more exciting!

5

On the other hand, AB+ can donate plasma to anyone.

Overall, I think they mostly try to encourage the double-red donations because the red cells are usually the highest demand, and by getting a double red they get 16 weeks worth of donation at once, instead of just 8, and it’s tough to get people to keep coming in every 8 weeks.