Abs to red Cell Ags Which are approximately 302 Ags , Can CauseHTRs and HDFN. The most important Abs are those of the ABO, RH,Kell, Kidd, Duffy and Ss blood group systems. Extended red cellPhenotyping of chronic patients and screening & identification of red cellAbs Shoud be done befor transfusion. Tubes, microplates , CAT and DNA techniques can be used for this purpose. Clinical bioassays can beUsed as a functional assessment for the significance of red cell Abs.