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n Medical Technology SA - A comparison of the gel (diamed-id micro typing system) and tube agglutination crossmatch
Background : The DiaMed-ID® micro typing system utilises a sephadex gel to capture agglutinate in a semi solid medium. This enhances visibility of agglutination compared to the traditional tube techniques. In the latter the agglutinate, particularly in weak reactions, is mixed with the free cells at the bottom of the tube, making visibility difficult. The tube technique has been the cornerstone of compatibility testing over the last 40 years, but the enhanced sensitivity of the gel technique has made the interpretation of tests more objective.
Study design and methods : This study aims to demonstrate how a combination of the two techniques can combine the advantages of both methods in the routine preparation of blood for transfusion to patients. The study compares cost, sensitivity and specificity of different combinations of techniques (Major Tube Cross-match, Major Gel Cross-match and Immediate Spin Crossmatch with antibody screening by the Gel method).
Results : The standard method detected 32 antibodies. The DiaMed-ID® system detected all the antibodies detected by the tube technique as well as a further nine antibodies undetected by the standard methods. The antibodies missed by the traditional tube method were all very weak and were from the Rhesus (Anti-D, Anti-C and Anti-E), Kell (Anti-Kell), Lewis (Anti-Lea) and Duffy (Anti-Fya) systems. No transfusion reactions were reported in these cases. Cost analysis indicated that the Immediate Spin Crossmatch with the DiaMed-ID® antibody screen was the most economical method, if the time factor is taken into consideration.
Conclusion : The Immediate Spin Cross-match was the fastest method to prepare blood for patients and therefore the most cost effective cross-match. The Gel Screening technique was the best method for detecting red cell antibodies and was therefore an improvement on the Tube Major Cross-match technique.
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