Blood Transfusion Two Sample Rule
The Two Sample Rule Myth Buster!
Why are Two Samples Needed?
The most crucial test undertaken in the Blood Transfusion Laboratory is the ABO group. An error in this test could result in an ABO incompatible transfusion, the consequences of which include organ failure, ITU admission and in 1 in 9 cases, death.
In 2012, the British Society of Haematology (BSH) and the British Blood Transfusion Society (BBTS) published new guidance on pre-transfusion sampling which stated 2 samples are required to confirm a blood group before group matched units can be transfused. This was in response to national data from the 2010 Serious Hazards of Transfusion (SHOT) report showing 386 cases of Wrong Blood in Tube (WBIT) occurred that year, each one representing a risk for the incorrect blood component to be transfused.
These samples must be collected as two independent events and following two independent ID checks, for example:
• Both samples can be collected by one staff member as long as they complete the ID checks fully before each venepuncture, i.e. ask the patient to state their name and date of birth before collecting each sample.
• Samples can be collected by different staff members who each conduct their own independent ID checks. Both staff members being present while one of them asks the ID questions constitutes 1 check.
How do I know if I need to take 1 or 2 samples?
ICE will show the request history for your patient. To make it easier to find, use the ‘Filter by speciality’ box as shown below.
It’s important to note the patient might have transfusion reports that don’t relate to a blood group – the only tests that count towards the 2 sample rule are Group and Save. This patient has a lot of requests including several Group and Saves:
When not to take a second sample
The patient above has several Group and Save reports visible in ICE, so only needs one sample on this occasion. Each year the transfusion lab receives around 800 duplicate samples, i.e. a second sample has been collected but isn’t required. That’s 800 occasions when a patient has been bled unnecessarily, which can be detrimental to patient comfort and has cost implications. A second sample is only required when there is no historical Group and Save in ICE.
How to ensure the sample is accepted by the lab
• Our primary method for labelling transfusion samples is Electronic Bedside Sample Labelling using the BloodTrack devices. This must be used in all inpatient areas. It is quicker and safer than manual labelling but does not replace the verbal ID checks.
• Positive patient identification – ask the patient to tell you their name and date of birth if they are able.
• Complete the process as instructed on the BloodTrack PDA. The steps have been carefully designed to promote safe practice.
• Complete the patient ID checks, sample collection and printing at the bedside without leaving the patient.
• Ensure the request form is completed fully and the details on the sample match the form.
• BloodTrack will print the details on the wristband – if the label that comes out the handheld printer is incorrect, that means the wristband is incorrect.
• ICE numbers cannot be used as an MRN under any circumstances.
• Do not pre-print labels or retain unlabelled samples
Do not try to ‘cheat’ the Two Sample Rule
The rule is in place to protect patients. In a dire emergency where taking 2 samples will delay patient care the transfusion lab will issue emergency group units. This is for emergencies only and not for routine use because the supply of emergency units is not infinite. Inappropriate/avoidable use of emergency red cells must be reported to SHOT, therefore the lab will follow up on all emergency stock usage.
