▪ Value

• The “Gold Standard” method to detect the presence or absence of blood group antigens on RBCs that has served the transfusion community well

• Simple and quick to perform, requires little in the way of equipment, and, when done correctly, has a specificity and sensitivity that is appropriate for the vast majority of transfusions

• Detects mixed populations of RBCs

▪ Reagents

• Specialized and obtained from immunized patients/donors (polyclonal and monoclonal antibodies) or from immunized mice (monoclonal antibodies)

• Source material is a biohazard and is diminishing

• Cost of FDA-approved, commercially licensed reagents is escalating

• Many antibodies are not commercially available and are characterized (often only partially) by the user and some are limited in volume, weakly reactive, or not available

▪ Limitations

• Is a subjective test

• Requires use of reliable antisera

• Labor-intensive testing so a relatively small number of donors can be typed for a relatively small number of antigens, which has limited the size of antigen-negative inventories

• Indirect indication of a fetus at risk of hemolytic disease of the fetus/newborn

• Difficult to phenotype a recently transfused patient

• Difficult to phenotype RBCs coated with IgG

• Can be difficult to distinguish an alloantibody from an autoantibody in antigen-positive people

• Restricted ability to determine zygosity, especially RHD zygosity in D-positive individuals

▪ Value

• Can be automated

• High throughput because multiple markers are tested simultaneously on one sample

• Computerized interpretation and data entry into a patient/donor data base

• Potential to precisely geno-match donor blood to the patient’s type

▪ Reagents

• Does not require special reagents, which can be readily purchased

▪ Limitations

• Predict an antigen type; it is recommended that the prediction be confirmed by hemagglutination, particularly if negative for the antigen

• Takes hours

• DNA and hemagglutination test results may not agree

• DNA results from somatic cells and from WBCs may not agree

• More than one genotype can give rise to the same phenotype, especially with the null phenotypes

• There is a high probability that not all alleles in all ethnic populations are known

• For research use only; has not been approved by the FDA as the sole test on which to base decisions regarding patient care