Table 1.
Features of hemagglutination and PCR-based assays for blood groups antigens.
| Hemagglutination |
| ■ 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 |
| DNA testing, including DNA arrays |
| ■ 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 |