The science of giving blood

Blood is vital: it has a variety of functions, from carrying oxygen around the body in red blood cells, to transporting our immune system’s soldiers, white blood cells and antibodies. It also contains small cell fragments, called platelets, and coagulation factors to help wounds to close. The average person has about 5 litres of blood. But you don’t need all of it. And sometimes other people do, as Adam Murphy found out at his first blood donation, before chatting about his donation with Steven Thomas, from NHS Blood and Transplant...

Adam - I've always wanted to be a blood donor, but until recently I haven't been able to. Now I live in Cambridge, I can. So I took a trip to the donor center there to give my first pint. Once I had been through the consultation process and had my iron levels tested, I sat in the chair with John - who was amazing throughout the whole thing - and started my first donation.

Adam [mid-donation] - And how am I going so far?

John - You’re romping along at 67 mils per minute, and you're just coming up to 300 mil.

Adam - When I had finished my donation - which was pretty painless - I sat down with Steve Thomas, Associate Director for Manufacturing Development at NHS Blood and Transplant, to find out what would happen to my blood next.

Steve - We'll have taken some sample tubes as well as the bag of blood. The tubes will go off to one of our main testing centers where they'll be screened for infectious diseases. The blood itself will go to a manufacturing centre where it'll be separated out into the different components of blood. So most people think of blood as being red cells; so those are the cells that carry oxygen, and what most people think of as a blood transfusion - if someone's losing a lot of blood they'll be given red cells quickly. A fraction of the blood will be separated to be pooled together with three other donations; a platelet fraction to make a platelet concentrate; and possibly the plasma will be separated - so that's the liquid that all the cells are suspended in - that then gets separated and frozen down as a fresh frozen plasma component, and again that's given to people who have deficiencies in their clotting, for instance.

Adam - Right. So that's red blood cells, which carry oxygen around the body; platelets, which help with clotting and forming scabs; and plasma, which is the liquid that the rest of the stuff travels in. Once out of the body and packaged up, the blood goes through a series of tests to check if you're infected with any viruses that might rule you out from donating the blood; how long you might have been infected for; and how your body was coping with the infection. I actually couldn't donate blood until moving to Cambridge from Ireland because I lived in the UK when I was a child. So what's that about?

Steve - So between 1980 and 1996 the food chain in the UK was proven to be contaminated with BSE. And so whilst we had to maintain a blood supply in the UK, and we were collecting blood from donors who lived here in that time as well, other countries excluded people who had lived in the UK in that time just to minimise the risk to their countries’ recipients.

Adam -  BSE - or bovine spongiform encephalopathy - might be more known as mad cow disease, and is a disease of the brain that cows get when they eat tainted products. That can be spread to humans where it's known as CJD or Creutzfeldt-Jakob disease, and it is a debilitating and terminal neurological condition.

Steve - It's been very difficult to develop a reliable test for variant CJD. And that's never been successfully brought to market. So there was a lot of work done on that over many years, but nobody ever got to the stage of having a reliable test.

Adam - So overall how is the UK doing when it comes to donation?

Steve - It's quite healthy. We are constantly looking for new donors because there is a turnover of donors. Hospitals are using less blood than before due to many initiatives to reduce unnecessary use of blood. But we still need 5,000 donations every day. We're also very keen to recruit donors from black and minority ethnic backgrounds because there is a high need for donors with those particular blood types, specific blood types, and so that's something that we're very keen to promote.

And we're also very keen to recruit more male donors, so many... there is a skew towards female donors rather than male donors joining the database, and so we're keen to encourage male donors. Primarily because they're more likely to be able to donate due to high haemoglobin levels, for their own safety, but also males are much less likely to have antibodies in their plasma that can cause adverse reactions in recipients. And that's due to females potentially making antibodies to paternal antigens on babies when they've been pregnant.