Problems highlighted when using anticoagulated samples in the standard tube low ionic strength antiglobulin test

Area of Science:

• Transfusion Medicine
• Immunology
• Clinical Pathology

Background:

• Current UK guidelines lack specific recommendations for sample type (clotted vs. anticoagulated) in antibody identification testing.
• The choice of sample can significantly impact the detection of certain antibodies, particularly IgM.
• Accurate antibody identification is vital for safe blood transfusion and antenatal management.

Purpose of the Study:

• To highlight cases where anticoagulated samples hindered IgM antibody detection.
• To emphasize the importance of using clotted samples for reliable antibody identification.
• To underscore the potential risks associated with inaccurate antibody screening in transfusion medicine.

Main Methods:

• Retrospective analysis of three patient cases requiring antibody identification.
• Comparative testing of both clotted and anticoagulated samples from the same patients.
• Serological investigation focusing on IgM antibody detection, including complement-activating antibodies.

Main Results:

• Detection of IgM complement-activating anti-S in two patients was impeded using anticoagulated samples.
• Detection of IgM complement-activating anti-Vel in an antenatal patient was also hindered by anticoagulated samples.
• Discrepancies between serum (clotted) and plasma (anticoagulated) results were identified upon parallel investigation.

Conclusions:

• Anticoagulated samples can lead to false-negative results for specific IgM antibodies, impacting transfusion safety.
• Clotted samples are essential for accurate identification of IgM antibodies, preventing potential transfusion errors.
• Adherence to using clotted samples in antibody identification testing is recommended for UK blood transfusion services.