Review: monoclonal reagents and detection of unusual or rare phenotypes or antibodies

Monoclonal antibodies have been used in the formulation of commercially available blood grouping reagents since the early 1990s. It became apparent early on that introducing them into routine use along with, or instead of, human- or animal-derived reagents could and did lead to discrepant reactions. These discrepancies most often came to light when confirming a blood type obtained previously with human- or animal-source reagents or when using two or more sources of a reagent from the same or another manufacturer to perform blood typing or antibody detection or identification testing. A number of factors contribute to differences in reactivity of reagents that are of the same specificity but are from more than one source. One factor is the use of different clones of the same specificity to manufacture blood bank reagents. Another is the effect of the various diluents used by different manufacturers to formulate reagents that contain the same clone(s). In addition, RBCs having unusual or rare phenotypes can cause discrepant reactions when performing phenotyping. Discrepant reactions can also occur because of patient or donor antibodies that react in an unusual manner when antiglobulin tests are performed with monoclonal antihuman globulin (AHG) versus rabbit AHG reagent. It is important to know the identity of the unusual or rare phenotypes and antibodies and to be able to recognize the different types of reactions that will be observed when using more than one reagent of the same specificity. Most importantly, one must be able to interpret reactions correctly and establish the true blood type of the RBCs or specificity of the antibodies. This review will describe situations in which the use of monoclonal reagents from more than one source or manufacturer, or comparison with results of human- and animal-source reagents, resulted in discrepancies with unusual or rare phenotypes or antibodies. Many of the samples described in this review were sent to the reference laboratory at Gamma Biologicals, Inc., in Houston, Texas, which later became ImmucorGamma with sites in Norcross, Georgia, and Houston, Texas. Immunohematology2006;22: 52–63.