What is the two-sample rule?

Bloodbank must ensure that there are TWO distinct samples from a patient that have generated the same blood group from both samples. If Bloodbank have seen the patient before and already have a historic blood group registered on the Laboratory Information System (LIMS), then only one group and save/X-match  sample is required as per normal protocol. If the patient has no previous records in Bloodbank then you MUST repeat the group and save/X-match with a second sample using a specific request form & sample bottle that will be provided by Bloodbank. This national recommendation is based on the evidence from:

  • The BEST studies as referenced in BSH Guidelines for pre-transfusion compatibility procedures in blood transfusion laboratories.
  • National data from the IBCT and the Near Miss chapters in recent SHOT reports (SHOT, 1996 to 2010) – 386 cases of “wrong blood in tube” (WBIT) were reported as near misses in 2010.
  • Local data confirms an unacceptable number of WBIT cases among patients where it can be detected due to having a historical group on record.

Why is this rule being introduced?

Wrong blood in tube (WBIT) is a ‘never event’, it should not happen, however on occasions it does. The consequences of transfusing somebody with blood of the incorrect blood group is very serious and can lead to death. In the 6 months prior to implementation, there were 4 WBIT incidents within the Trust, 2 of which would have resulted in a major ABO incompatible transfusion if blood products had been requested. WBIT is a SHOT (Serious Hazards of Transfusion) reportable incident. The two-sample rule is a national guideline to improve patient safety when receiving transfusions and has been routinely adopted by the majority of NHS Trusts across the UK.

How does the two-sample rule work?

If the patient is not known to Bloodbank then the two-sample rule is invoked. The two samples must come from separate venepuncture events and ideally should be carried out by two different people. A specific request form & sample will be issued by the laboratory and should be collected from Bloodbank upon delivery of the 1st G&S sample in urgent situations or as required for routine requests. If a cross-match request or group & save request with clinical details implying the patient will be undergoing surgery within the next 24hrs is received and this is the first time Bloodbank has seen the patient, then Bloodbank will notify the clinical area informing them that a ‘check group’ is required. It is then the responsibility of clinical staff to organise collection of this sample bottle.

It is NOT acceptable to take two samples at one venepuncture event and send them to Bloodbank on separate request forms. This will not negate the possibility of WBIT.

How will I know if a second sample is required?

If you are unsure if Bloodbank already have a historic blood group, clinical staff can check ICE for previous requests or contact the laboratory to confirm.

What happens in an emergency situation?

If blood is required in an emergency e.g. Major Haemorrhage protocol activation, the two-sample rule will still apply, however, the Bloodbank will only be able to issue Group O red cell products and AB plasma products in the absence of a check group sample. It is the responsibility of clinical staff to organise collection of the ‘check group’ bottle. Blood will be issued as per the MH protocol and will not be delayed.

Why can’t I use one of our own bottles?

The 2 sample rule needs to involve two separate venepuncture events. ‘Check Group’ request forms and bottles are specially labelled by the Transfusion Laboratory and are signed for upon collection by clinical staff. This is to assure the Laboratory that the second venepuncture event involves a different sample and that clinical staff are not obtaining two G&S samples from the same venepuncture site at the same time and labelling them with different times.

These steps are in place solely for patient safety.

Check groups are there for patient safety and follow the same strict labelling, zero tolerance policy as for normal group and screens – NO EXCEPTIONS.