Bombay Blood Group: A Report of Two Cases.

Timely detection of rare blood groups can be lifesaving, as individuals with these groups can only receive blood products from donors within the same group. The Bombay blood group is characterized by the absence of A, B, and H antigens on the surface of RBCs and can be easily missed in routine blood grouping if only forward grouping is performed. In reverse grouping, it is necessary to test the patient's serum with pooled O cells to differentiate between the O and Bombay blood groups. Further workup is conducted by testing the patient's red cells with anti-H lectin (antisera), where the absence of an agglutination reaction suggests the Bombay phenotype. In blood group O testing, the patient's blood serum mixed with pooled O cells yields no agglutination reaction in reverse typing, whereas testing RBCs with anti-H lectin results in a strong agglutination reaction, as H-antigen is present at its highest concentration in these individuals. Correct diagnosis of such rare blood types can save patients' lives as well as prevent the consequences of a wrong blood transfusion. Here we present two cases that were diagnosed as having the Bombay phenotype on blood group testing in our blood bank. Both were initially misdiagnosed as blood group O by an outside laboratory. Correct diagnosis of rare blood groups in blood banks is imperative, as a misdiagnosis can result in fatal outcomes.