A recent study suggests a more thorough, extended typing kit may become available that will type for DEA 1.1, 3, 4, and 7 and Dal.¹⁸ An appropriate dilution for the DEA 1.2 typing reagent was not identified, and DEA 5 was not included. In this study, 10 dogs received DEA 1.1 compatible transfusions and were crossmatched before and after transfusions. Six of the crossmatch pairings in four of the dogs could have developed antibodies based on the typing results, and four crossmatches involving two dogs became incompatible 21 to 23 days later with reaction strengths ranging from 3+ to 4+. A third dog had a 1+ incompatibility at day 13 that became compatible by day 50. Five crossmatch pairings in four dogs were not expected to develop antibodies based on the extended typing results; however, major incompatible crossmatch results were obtained ranging in strength from 1+ to 3+ over the course of two to four weeks. These incompatible results indicate sensitization to antigens not detected by the typing process (e.g. DEA 5, 6, 8).

Even though these typing methods are relatively simple, read the package inserts thoroughly for sources of potentially erroneous results and follow the instructions exactly. When confirmatory testing is necessary, such as for selecting permanent donors, for checking questionable results, or in lieu of in-house typing for elective surgeries, outside laboratories such as Animal Blood Resources International in Stockbridge, Mich., or the University of Pennsylvania's Hematology and Transfusion Laboratory may be used. The extended blood typing kit option may expand these possibilities to other testing sites.

A major crossmatch tests for detectible naturally occurring or induced antibodies in the recipient serum against donor erythrocytes. This testing should be done any time a patient is likely to have relevant naturally occurring antibodies (cats), if the patient's transfusion history is unknown, or if a transfusion occurred at least two to four days previously, even if it was with the same donor.^1,8,19,20 Commercial crossmatch kits are available from DMS Laboratories.

A slide crossmatch is a crude method of crossmatching that should be reserved for emergency situations only. In this case, the major slide crossmatch consists of mixing two drops of recipient plasma with a drop of blood from the donor at room temperature on a clean glass slide and observing for agglutination while rotating the slide for one minute. A minor crossmatch can be performed in the same way using two drops of donor plasma and one drop of recipient blood. However, two potentially serious errors can occur with this method. First, potentially fatal hemolytic reactions may be missed since hemolysis is difficult to recognize by using this method. Second, this procedure can miss prozone reactions where the presence of excess antibody for the amount of antigen can result in failure of agglutination.