Issued August 2010
1. “Recipient ABO (D) group must be confirmed (by repeat testing) prior to electronic issue of blood components. This may be achieved by testing replicate samples separated by time or by verifying the ABO/Rh results using different reagent clones on the same patient sample.”
Q. Please could you provide further clarification on the intention of the ‘same sample’ and ‘two sample’ approach.
Same sample approach - Is that the first determination of the ABO Rh D blood group on this sample is being performed with a full ABO forward and reverse test, which includes an appropriate negative control. The repeat testing on this sample can be performed with an abbreviated ABD confirmation test. Can you please confirm that our interpretation is in line with the requirements of the guidance document?
A. Yes this is correct, however, the guidance also notes that this approach does not provide protection against the possibility of undetected ‘wrong blood in tube’, although this risk also exists in cases of blood transfusions which are cross matched against a new patient’s first blood sample.
Two sample approach - Is this approach that the first determination of the ABO Rh D blood group is being performed with a full ABO forward and reverse test, which includes an appropriate negative control. The repeat testing can also be performed with an abbreviated ABO & D confirmation test. However, in contrast to the same sample approach, must be performed on a sample from a different venepuncture, in order to detect a potential sample collection error.
A. Yes, although the test used for the abridged confirmatory test must be CE marked for this purpose, i.e. CE marked for confirmation of ABO Rh D group on a new sample; not just confirmation of the ABO Rh D group on the same sample which has already been fully grouped using forward and reverse testing.
Q. Can you please provide further clarification if separation by time is defined in length, i.e. there seem to be various interpretations of separation by time, for which some interpret this as very short period (same patient for same blood request) and others also interpret this as an extended period of time, i.e. 6 months between two admissions.
A. ‘Separation by time’ is intended to be different venepuncture events, i.e. the collection of 2 consecutive samples during a single venepuncture would not provide protection against ‘wrong blood in tube’ incidents. The adoption of the two sample approach has the benefits of providing protection against the possibility of undetected ‘wrong blood in tube’.
Q. For each of these methods could you please explain your intended deliverables?
A. We expect transfusion laboratories to implement an approach to pre-transfusion testing which meets the intent of the guidance. The purpose of the guidance is to provide assurance of a robust determination of ABO & Rh D group.
2. Same sample approach and use of different clones - For the same sample approach the guidance document states that verification of the ABO Rh results on the ‘same patient sample’ should be performed using different reagent clones.
Q. Please can you further clarify your intention for this statement?
A. It is our understanding that there are confirmatory cards suitable for confirming the blood group of a specific sample, which are not suitable for sole use in determining the ABO/D group of subsequent samples from the same patient. This is due to the possibility for DAT+ve samples to appear as Rh D+. It is expected that transfusion laboratories should understand the limitations of their testing systems, and use them for appropriate applications.
Q. If we use a cassette where each well has a mixture of 2 different clones for anti-A and anti-B does this meet the intention of the guidelines?
A. this appears to meet the intention of the guidance.
Q. If we use a cassette/card for anti-D with only one reagent clone in the confirmatory test (same as Initial test for ABO&D) are we correct that this does not meet the guidance issued?
A. The MHRA guidance for the ‘single sample approach’ states that robust ABO RhD determination may be achieved using the testing approaches suggested (such as the use of a different reagent clone), however a laboratory should justify it’s approach to testing to demonstrate that it achieves the equivalent level of assurance. Alternative strategies would be accepted if scientifically justifiable and based on a documented risk-based assessment.
Chair of NHS Operational Impact Group