Lewis blood group determination in bloodstains by planimetric measurement of eluted monoclonal antibodies

Planimetric measurements were employed for reading the results of an elution test to determine Lewis blood groups in dry human bloodstains. In the absorption-elution test, two varieties of indicators were used to detect eluted Lewis antibodies. First, 64 blood-stains aged between 2 to 8 months were tested with glutaraldehyde (GLA)-treated erythrocytes (planimetric hemagglutination assay, PMHA). This method demonstrated that dry stains weighing approximately 0.4 mg (equivalent to 3 microliters of whole blood) were sufficient for detection of Lea or Leb antigen. Results were obtained within 1 h. Then, 37 of these stains were tested with Lewis substance-coated latex particles (planimetric latex agglutination assay, PMLA). The presence of Lea and Leb antigen were detected from dry stains weighing 0.1 mg (equivalent to 1 microL of whole blood) within 3 h. Both these assays are faster and simpler with accuracy than the enzyme-linked immunosorbent assay (ELISA). Latex particles coated with Lewis substance are, in particular, strongly agglutinated and show agglutination patterns more clearly than erythrocytes. The blind tests using these two methods properly classified 7 Le(a + b-) and 23 Le(a-b + ) bloodstains; whereas, 5 Le(a-b-) stains were undetermined by the criteria for these tests. These results indicate the usefulness of the PMHA and PMLA for typing Lewis blood groups from small bloodstains.