A handy chart for the interpretation of sequential differential adsorption–elution procedure

D adsorption and elution procedures are often helpful in separating multiple antibodies in a complex mixture. One of the applications of this procedure is to confirm the presence or absence of anti‐D, anti‐C, and anti‐G in the serum with apparent anti‐D + anti‐C specificities in alloimmunized pregnancies.[1] We performed a modified sequential differential adsorption‐ elution procedure in such patients. Unlike the method described in the literature, to begin with, we used enzyme‐treated red blood cells of DEc phenotype for the adsorption, and the procedure (with the cell to serum ratio of 1:1) was repeated twice to achieve the complete adsorption of the antibody in the serum. The eluate obtained by cold acid elution technique from these cells was used for the second adsorption procedure with dCe cells. Following each step, the adsorbed serum and the eluate were tested against the D+C‐ and D‐C + screening cells. We validated this procedure using the known mixture of antibodies and the samples from five antenatal cases. Baia et al. have explained a simple approach to confirm the presence of anti‐D in sera with the presumed anti‐D and anti‐C specificity.[2] However, it requires two aliquots of serum to rule out all the five possible combinations: anti‐D + anti‐C, anti‐G, anti‐C + anti‐G, anti‐D + anti‐G, and anti‐D + anti‐C + anti‐G. We used only one aliquot (1.5 mL) of serum, and the total turnaround time was 6 h in the protocol mentioned above.