Inheritance of a rare gene (hh), RBCs are devoid of ABH antigens and therefore fail to react with anti-A and Anti-B and anti-H, No ABH Antigens but with anti-A, anti-B and anti-H
hh genotype, No H antigens formed, therefore no A and B antigens, Phenotypes as blood group "O", Anti-A, anti-B, anti A,B and anti-H present in the serum, Can only be transfused with blood from another Bombay (Oh)
ABH soluble antigens can also be found in all body secretions, Presence is dependent on the ABO genes inherited and inheritance of another set of genes (SeSe,Sese), ABH substances can be detected in the following body fluids (saliva, tears, urine, digestive juices, bile, milk, Pathologic fluids: pleural, peritoneal, pericardial, ovarian cyst)
Saliva-sample: 3-5 mL of Saliva, ask the patient to gargle using NSS or water, less viscous compare to sputum, subject heating to inactivate enzymes (CHONS)
Often associated with unexpected reactions in the reverse grouping due to weakly reacting or missing antibodies, More common in newborns, elderly patients, patients with leukemia, ABO subgroups, patient with hypogammaglobulinemia or aggamaglobulinemia
Enhance reaction by incubating patient serum with reagent A and B cells at room temp for 15 to 30 minutes, An autocontrol and O cell control must be tested concurrently
Often associated with unexpected reactions in the forward grouping due to weakly reacting or missing antigens, Causes: Subgroups A or B, Leukemias may yield weakened A or B antigens, Hodgkin's disease, "Acquired B" phenomenon (often associated with diseases of the digestive tract)
Discrepancies between forward and reverse grouping caused by protein or plasma abnormalities and result in rouleaux formation, or pseudoagglutination, Causes: Elevated levels of globulin (e.g., multiple myeloma, Waldenstrom's macroglobulinemia, other plasma cell dyscrasias and advanced cases of Hodgkin's lymphoma), Elevated levels of fibrinogen, Wharton's jelly in cord blood samples, Plasma expander's (dextran and polyvinylpyrrolidone)
Discrepancies between forward and reverse grouping are due to miscellaneous problems, Causes: Cold reactive antibodies, Patient has circulating RBCs of more than one ABO group due to RBC transfusion or bone marrow transplant, Unexpected ABO isoagglutinins, Unexpected non-ABO alloantibodies