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Tech Tips: Neutralization/Inhibition: No red cell clumping is a positive test!

A Blog from Eric Ching:

In a recent presentation at CSTM annual meeting, I talked about the “p” value in antibody identification. The p value refers to the probability of making an error in the interpretation of a panel result by chance. Hospital blood banks use p value less than 1 in 20 chances or p= 0.05 as minimal requirement while reference laboratories use p< 0.01 as their antibody identification guideline.

The only definitive antibody identification (p=0) is by the use of a specific soluble antigen to neutralize or inhibit the antibody in question. For example, the use of P1substance to abolish the plasma reactivity is a definitive proof of anti-P1​:
  Plasma + P1 substance Plasma + Saline Interpretation
Positive Test 0 1+* Anti-P1
Negative Test 2+ 1+ Not anti-P1
*Dilution control: a negative result invalidates test

Specificity Source
A,B,H,P1,Lea,Leb Commercial, Saliva
Sda Pooled, dialyzed and pH adjusted urine
Chido/Rogers, Cromer Pooled plasma or serum

Known Ch- and Rg- plasma failed to neutralize plasma in question is a definitive proof:
Titre 1 2 4 8 16 32 64 128 256
0 0 0 0 0 0 0 0 0
Ch- 2+ 2+ 1+ 1+ 1+ 1+ 1+ 0 0
Rg- 0 0 0 0 0 0 0 0 0
Saline 2+ 2+ 1+ 1+ 1+ 1+ 1+ 0 0
Interpretation: Anti-Chido failed to be inhibited by Chido negative plasma
Neutralization by recombinant soluble blood group protein s - a game changer of future antibody identification?
Recombinant soluble blood group proteins (rBGP) are now available in Europe; single rBGP of K, k, Fya, Fyb, Inb, Yt, Sc, Doa, Dob, Rg, Ch, Cr, Kn and JMH are now available for definitive identification of alloantibodies against these blood group antigens. Automated platforms using rBGP and column agglutination technology, enzyme-linked immunosorbent assay, colour-coded microsphere as well as protein micro arrays may revolutionize future blood group antibody identification. (Transfusion 2014; 54:1823-30)

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