Individuals could be classified as 'secretors' and 'nonsecretors'according to their ability to secrete ABO blood group antigens in saliva  ABO blood group antigens (A, B, and H), in addition to their presence on blood cells and platelets, are also present on other tissue cells and are variably expressed through body fluids, such as saliva, tears, semen, urine, gastric juice, and breast milk, depending on whether the individual possesses the secretor gene or not, the inherited A, B, O genes,and Lewis blood group system 
Similarly, Lewis blood groups were determined according to tube method.
11] demonstrated that the association of the Lewis blood group
with infertility in among groups was not statistically different, but Khan et al.
Ten per cent of the white population lack the Lewis blood group
antigen and are unable to produce CA 19-9, even in the presence of malignant disease.
Recently, molecular genetic studies were carried out to determine the role of the H, Se and Le genes in the expression of H antigen in secretions and Lewis blood group
antigen on erythrocytes.
Daniels (Bristol Institute for Transfusion Services) and Bromilow (DiaMed AG) describe the ABO, Rh, Kell, Duffy, Kidd, MNS, Diego, and Lewis blood group
systems, and explain the clinical significance of blood group antibodies causing hemolytic transfusion reaction and hemolytic disease of the fetus and newborn.
The investigators compared the risk of cardiovascular mortality among men with different Lewis blood group
81, which indicates that there is good agreement between the two methods of determining the Lewis blood group status.
Differential tissue expression of the Lewis blood group antigens: enzymatic, immunohistologic, and immunochemical evidence for Lewis a and b antigen expression in Le(a-b-) individuals.
A cloned human cDNA determines expression of a mouse stage-specific embryonic antigen and the Lewis blood group all/1,4)fucosyltransferase.