Use of Staphylococcal Protein-A and Streptococcal Protein-G for Detection of Red Blood Cells (RBC) Antibodies and Comparison with Other Techniques

Background: Detection of red blood cells antibodies is important for the diagnosis of autoimmune hemolytic anemia, hemolytic disease of newborn, pre-transfusion testing and other problems. The aim of this study was to use Staphylococcal protein A (SpA) and Streptococcal protein G (SpG) as reagents in immunological tests for detecting red blood cells (RBC) antibodies and to compare the method with other techniques.
Study Design & Methods: Sera from 60 patients, comprising forty-four anti-D positive sera from pregnant women and 16 from healthy controls were, used for the study. The anti-globulin gel test and the standard Coombs’ test were used to determine RBC antibodies in these sera and the result were compared with that of protein A and protein G tests.
Results: With various degree of agglutination all 4 techniques detected the presence of RBC antibodies (anti-D) in the sera from 44 pregnant women, and tested negative for the remaining 16 sera (from healthy controls). The sensitivity and the specificity of the 4 techniques was 100%.
Conclusions: This preliminary study demonstrates that both SpA and SpG tests can be used for the detection of RBC antibodies and therefore requires more study and testing before they can become useful standard tests in transfusion medicine.