Comparison of NIH-CDC and AHG-CDC methods for the Detection of Panel Reactive Antibodies

Han, Tae Hee; Kim, Sun Mee; Lee, Young Joon; Park, Myoung Hee

Abstract

BACKGROUND
Panel reactive antibody (PRA) test is used for anti-HLA antibody screening and characterization in patients awaiting organ transplantation. Complement-dependent cytotoxicity (CDC) is the most widely used standard procedure and addition of antihuman globulin (AHG) reagent to the basic (NIH) CDC method increases the sensitivity of detection of HLA antibodies. We compared NIH-CDC and AHG-CDC methods for the detection of HLA class I panel reactive antibodies.
METHODS
A total of 314 sera from 253 patients were analysed for the detection of HLA class I antibodies by NIH-CDC and AHG-CDC methods using a panel of 50 lymphocytes. PRA% and reaction strength (mean score) were calculated and antibody specificities were identified with r value calculated for antibody specificity.
RESULTS
A total of 46 (15%) out of 314 sera were PRA-positive (PRA%> or =10%) by either NIH-CDC (33 sera) or AHG-CDC (43 sera). Concordance of PRA test results between these two methods was 96% (301/314). AHG-CDC was more sensitive in the detection of HLA antibodies compared with NIH-CDC, showing significantly higher PRA% (44% vs 29%, P=0.0001) and reaction strength (mean score 7.3 vs 6.1, P=0.0015) for PRA-positive samples. Among 46 PRA-positive sera, HLA antibody specificities were identified in 21 samples (46%) by NIH-CDC and in 32 samples (70%) by AHG-CDC. AHG-CDC methods frequently detected a wider range of antibody specificities compared with NIH-CDC and provided a more accurate assessment of the antibody specificities. Follow up PRA tests were useful providing information on change of alloimmunization status and antibody specificities in prospective organ transplantation patients.
CONCLUSIONS
Compared with NIH-CDC, AHG-CDC method is more sensitive in the detection of panel reactive antibodies and provides a more accurate assessment of the HLA antibody specificities.