Group and save blood test explained: why it is done before surgery

A group and save test is carried out in the hospital transfusion laboratory on a sample of your blood. It has two parts. First, the laboratory identifies your blood group, which North Bristol NHS Trust describes as the determination of blood group. Second, it screens your blood for antibodies, because some people have antibodies that could react with donor blood. North Bristol states that the test is required for the determination of blood group and antibody status and for the provision of blood and components.

The names vary by hospital. North Bristol lists the test as Group and Hold, also known as Group and Save or blood grouping. York and Scarborough list it as Blood Group and Antibody Screen (Group and Save). Despite the different names, the purpose is the same: to have your blood group and antibody status on record so that suitable blood can be provided without delay if it becomes necessary.

Having a group and save does not mean you will be given blood. It is a preparatory test. It sits alongside other pre-operative tests such as a full blood count and kidney function; the related page on the pre-surgery blood panel lists those.

The NHS explains the reason in its transfusion guidance: a blood transfusion can help if you have lost a lot of blood, from an accident, surgery or giving birth, or if you have conditions that affect the blood or bone marrow. It adds that you will have a blood sample taken before starting a transfusion to check that the donor blood is the right blood group for you.

A group and save sample is taken in advance, so the laboratory has the information if bleeding unexpectedly occurs. That is why it is commonly requested before operations where blood loss is possible. Whether you need one depends on your operation, your health, the policy of the hospital and the advice of your pre-assessment team.

Antibody screening matters because antibodies can make it harder to find compatible blood. The York directory states that detection of atypical antibodies and incompatibilities may cause unexpected and inevitable delays, which is a reason that the test is done ahead of time rather than at the moment blood is needed.

The blood sample is taken from a vein in the same way as any other blood test. The test directories describe a single EDTA tube, with North Bristol specifying a 6 mL pink-topped container and an ideal volume of 4 mL, and York specifying a minimum volume of 4.9 mL for adults and noting that smaller volumes of about 1 mL are acceptable for paediatric patients.

A sample does not last indefinitely. North Bristol says samples can be valid for up to 7 days, reduced to 3 days if the patient has been transfused in the preceding 3 months or is pregnant. York lists stability of up to 7 days and notes it is largely dependent on the patient's serological status and recent transfusion history. Leeds sets out the same rule: a sample taken within 7 days before a transfusion is acceptable, except for pregnant women, recently transfused patients and patients within 3 months of a solid organ transplant, for whom the 72-hour rule remains.

In practice this means that a group and save taken at a pre-assessment visit weeks before an operation may not be usable on the day, and the sample may have to be repeated on admission. That is a routine step and not a sign that something was missed.

The two-sample rule is a safety step. Leeds Teaching Hospitals explains that the blood bank must ensure there are two distinct samples from a patient that have generated the same blood group before ABO-matched components are issued. The aim, it says, is to ensure that the blood components matched by the laboratory are as accurate and as safe as possible.

North Bristol's directory points staff to a "two sample myth buster", which suggests the rule is sometimes misunderstood and may apply differently depending on the patient's history and local policy. If a second sample is requested, ask the team to explain why; it is a standard safety step rather than a sign of a problem.

Turnaround times differ. York quotes 45 minutes for urgent requests and within 4 hours for routine ones, while North Bristol quotes 24 hours and Leeds quotes 24 to 48 hours for routine GP requests. These are laboratory figures and not necessarily what you will see in practice.

The result is not a pass or fail. It records your blood group and whether antibodies were found. If an antibody is found, identifying compatible blood can take longer, which is why the York directory warns of possible delays, and the team plans around it.

If you do need a transfusion, the NHS says it usually takes up to 4 hours, and the staff check your pulse, temperature and blood pressure before, during and after. The NHS describes it as a generally very safe procedure, with complications that are rare, and lists the symptoms that should prompt urgent advice afterwards, such as a high temperature, aching muscles, blood in the pee or breathlessness.

Ask your pre-assessment nurse or surgeon whether you need a group and save, when it will be taken and whether it will need repeating on admission. They can also explain whether it is likely that you will need blood for your particular procedure.