Type and screen method and Coombs crossmatch method for pretransfusion testing: A prospective comparative study in a tertiary care hospital in Delhi.

BACKGROUND

The aim of pretransfusion testing (PTT) is to prevent the immune-mediated hemolytic reaction by the transfusion of incompatible donor red cells. The methods of PTT have evolved over the years and a new method of type and screen (T and S) was introduced, in which only ABO grouping, Rh typing, and antibody screening would be carried out with omission of routine Coombs crossmatch. Although T and S is an accepted method for PTT in developed countries, only a few studies in literature have evaluated its efficacy in India.

AIM AND OBJECTIVE

The aim of the study was to compare T and S method with conventional Coombs crossmatch method for PTT.

MATERIALS AND METHODS

Two thousand and fifty samples were randomly selected from the samples received in blood bank for requisition of blood transfusion after taking informed consent. ABO blood grouping and Rh typing were performed for each recipient's sample. "T and S" and "Coombs crossmatch" were done simultaneously by two different persons without knowing the result of each test. A commercially available three cell panel was used for antibody screening, in which the recipient's plasma was reacted with red cells in the low ionic strength solution Coombs Gel card at 37°C by column agglutination technology.

RESULTS

Antibody screening was positive in 29 (1.41%) patients and negative in 2021 (98.59%) patients. Out of 29 patients, 27 had alloantibodies and 2 had autoantibody. Most common alloantibody found in our study was anti-D. Other antibodies found were anti-K, anti-C + D, anti-E, anti-C, anti-c, anti-Jk, and anti-Mi (a). Crossmatch on first attempt was compatible in 2028 (98.93%) patients and incompatible in 22 (1.07%) patients. Out of 29 patients who were positive for antibody screening, crossmatch was incompatible in nine patients. Crossmatch was compatible in twenty patients, who had positive antibody screen. However, crossmatch compatibility in these patients, reflect either absence of corresponding antigen or antigen present in low dose (heterozygous) in donor blood. On the other hand, out of 22 patients incompatible on first crossmatch, antibody screening was negative in 13 patients and was positive in only nine patients. Hence, 13 patients with antibody would have been missed by antibody screen alone. Kappa statistics was used to compare the efficacy of "type and screening" and "Coombs crossmatch." It showed κ =0.445 ( < 0.001) implying moderate agreement between the two variables of "T and S" and "Coombs crossmatch."

CONCLUSION

T and S is a scientifically better method but needs to be implemented with caution. We need to develop our own cell panels having adequate representation of indigenous antigen (including In, Mi (a), etc.,). Large-scale studies need to be done in India with indigenous screening cells to evaluate efficacy and safety of T and S method.