Statement: The Ro subtype explained

Friday, 04 Dec 2015

The Ro subtype is simply blood with a certain combination of genes.

What makes donors with the Ro subtype special, is the fact that only 2% of our donors have it.

Understanding blood types

To explain what the Ro subtype is, we need to start by explaining a little bit more about blood.

There are 36 known blood group systems that make up your blood. For blood transfusion the best known and most important blood group systems are the ABO group and the Rh group.

The ABO group determines whether you belong to blood group A, B, O or AB.

Specifically, the RHD gene of the Rh group determines whether someone has + or - blood. If the RHD gene is present, it is positive (+) and if the RHD gene is absent, it is negative (-).

So together, the ABO group and the Rh group create these eight, commonly known blood groups:

 

A+ A- B+ B- AB+ AB- O+ O-

 

Usually, when a patient requires a single blood transfusion, they can be given blood based on only the ABO group and Rh group.

But when a patient requires multiple blood transfusions, they need to be given more extensively matched blood. Subtypes of all of the blood group systems are taken into consideration, when determining the most suitable blood to give to the patient.

What is the Ro subtype?

So there’s a little bit more to the Rh group. It is actually comprised of two genes: in addition to the RHD gene, there’s the RHCE gene.

As we said above, there are only two possibilities for the D gene, it can either be present (D) and thereby making the blood type positive (+), or absent (d), thereby making the blood type negative (-).

 

D d

 

The RHCE gene, however, is more complex, and can result in one of four variations of the C, c, E and e antigens (these are tiny protein markers on the surface of your red blood cells), which are:

 

ce Ce cE CE

 

So when the two different genes combine there are eight possible antigen outcomes:

 

Dce DCe DcE DCE dce dCe dcE dCE

 

These gene combinations were discovered in 1943 by American scientist Alexander Wiener (a colleague of Karl Landsteiner, who originally discovered the ABO system). In order to try to simplify the system Dr Wiener assigned them the following names:

 

Dce DCe DcE DCE dce dCe dcE dCE
Ro R1 R2 Rz r r' r" ry

 

Thus, when the RHD and RHCE genes combined produce ‘Dce’, this is what Wiener coined Ro and we call the Ro subtype.

From the 'Dce' you could also infer that if someone has the Ro subtype, they have to have the RHD gene and thereby a positive blood group. This means that people with the Ro subtype always have to have either A+, B+, AB+ or O+ blood.

Why are subtypes important?

When a patient requires a blood transfusion, they can usually be given blood from a donor based on their ABO group and Rh type only.

With some medical conditions, however, patients can require ongoing multiple blood transfusions, sometimes for the rest of their lives. These patients need to be given more extensively matched blood. So, if a patient has the Ro subtype and requires ongoing multiple transfusions, usually they need blood of the Ro subtype.

Who needs the Ro subtype?

One example of a need for regular, ongoing transfusions is the management of sickle cell disease. If a patient with sickle cell disease has the Ro subtype, ideally blood of the Ro subtype should be given to the patient.

What is sickle cell disease?

Sickle cell disease is an inherited disorder of haemoglobin. Individuals with sickle cell disease have abnormal, or 'sickle shaped', red blood cells. The abnormal red blood cells cannot transport oxygen around the body, have a shorter lifespan and aren't replaced as quickly by the body as normal, healthy red blood cells. This can cause mild to severe anaemia.

Furthermore the abnormal red blood cells are unable to move around as easily as normal, healthy red blood cells, and the abnormal shape can block blood vessels. The painful 'sickle cell crisis' lasts on average five to seven days, and can cause tissue and organ damage.

Patients with sickle cell disease usually depend on ongoing transfusions for the rest of their lives. So if a patient with sickle cell disease has the Ro subtype, they need blood that is more extensively matched.

Please note that the Ro subtype and sickle cell disease are not connected. Just to clarify, if you have the Ro subtype this does not mean that you have sickle cell disease, or vice versa.

Who has the Ro subtype?

As of January 2016, 2% of the regular blood donors in England have the Ro subtype.

The Ro subtype is more than 10 times as common in individuals from Black African or Black Caribbean ethnic backgrounds, than in individuals from White ethnic backgrounds.

It's vitally important that the people from whom we collect blood are representative of the population of the UK as a whole, and the need for Ro blood in the management of sickle cell disease is just one of the many reasons why we encourage more individuals from Black African and Black Caribbean ethnic backgrounds to start donating blood.

What does this mean for donors with the Ro subtype?

As part of a new initiative to inform donors more about blood and who benefits from their donations, we have started to tell donors if they have the Ro subtype and what this means. We hope that donors with the Ro subtype will continue to give blood as regularly as possible. We may also, in times of particular need, contact these donors outside of their usual donation pattern and ask them to make a special effort to donate. Ro blood is rare among the donors, and there are patients in real need of it.

We would also like to emphasise that the Ro subtype is simply blood with a certain combination of genes, and is perfectly normal. The Ro subtype does not affect an individual’s blood type or how it works. Furthermore having the Ro subtype does not mean that you have a disease, for example having the Ro subtype and having sickle cell disease are not connected.

We hope that nobody finds themselves in the situation where they need a blood transfusion, but if someone does, we will always be able to provide them with the blood they need.