Background:Pre–transfusion compatibility testing is performed in order to prevent the transfusion of incompatible donor RBCs. It can assure ABO compatibility between donor and patient blood as well as detect most clinically significant red cell alloantibodies.

Aim: To estimate the incidence and nature of red cell incompatibilities that were reported in the cross match lab.

Settings and Design: This single centre prospective study has been conducted at the Department of Transfusion Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati during the period from June 2016 to November 2018.The study population comprise of recipients of whole blood and packed red cells whose requests were sent to Immuno–Haematology laboratory for pre–transfusion testing.

Material and Methods: Two millilitre of plain blood sample from each recipient was collected separately for pre transfusion testing according to our departmental SOPs. Whenever an incompatibility was identified at any stage of pre transfusion testing, the reasons were analyzed. Results were expressed as percentage.. Statistical analysis was carried out using SPSS version 25, SPSS Inc, Chicago, USA.

Results: During the study period, 24,528 cross matchings have been done among which a total of 42 (0.17%) incompatibilities occurred. Incompatibilities occurred with sample of the patients from 4 years to 70 years with eight males and sixteen females. Majority of incompatibilities were due to unexpected antibodies and majority of them belong to O blood group.

Conclusion and Recommendations: For patients who are unlikely to require blood transfusion in a given medical or surgical setting, “type and screen” should be a common approach. This practice of performing type and screen only allows better inventory management of red blood cell supply.