Gel is known to display stronger D reactivity than both solid phase and tube. I've heard the explanation is due to the pentamer form of IgM, which is trapped in gel causing a stronger positive. Galileo/Neo/Echo and tube all use hemagglutination. I've also seen this when moving from Galileo to gel. If we didn't already have Rh Neg and Weak D histories on our patients and donors from the Galileo, we likely would've missed these Weak D patients in gel, scary! Our protocol with gel was to retest all D reactions less than or equal to 2+ by another method. Then molecular genotype RHD for those suspected as Weak D.
