Analysis of Discrepant Results between Enzyme Immunoassay and Anti-human Globulin -Complement-ependent Cytotoxicity Method for Panel Reactive Antibody Test

Hwang, Sang Hyun; Jang, Seongsoo; Oh, Heung Bum; Im, Young Hee; Won, Chin Yon

Abstract

BACKGROUND: Panel reactive antibody (PRA) test is important in that it could minimize the errorneous report of HLA crossmatch in emergent situation and be used as a information on nationwide organ sharing. However, only a few laboratories manage to do this test by home-ade tray. This study was intended to resolve the cause of discrepancy between EIA and AHG-DC which would be encountered when supplement AHG-DC was tested for EIA positive samples.
METHODS
Reactivity of Lambda Antigen Tray class I and class II mixed (LAT-, One Lambda, CA, USA) was evaluated to 23 specimens which had been positive in AHG phase of HLA crossmatch. All the samples for PRA were tested by EIA screening kit primarily and then AHG-DC was applied only in EIA positive samples. Samples showing discrepant results between two tests were further evaluated by EIA identification panel, platelet absorption test, dithiothreitol (DTT) treatment, and HLA crossmatch (AHG-DC and flowcytometry) with lymphocytes having antigen specificity reactive to antibodies identified by EIA kit.
RESULTS
Of 23 samples, 21 (91.3%) showed strong reactivity to EIA and remaining 2 were confirmed to have IgM type alloantibodies. Of 92 samples for PRA, 22 (23.9%) were positive in anti-LA class I. 10 of 22 samples with positive EIA showed negative results by AHG-DC. While three of them were identified of their antibody specificity, of which 2 samples confirmed to have CYNAP (cytotoxicity negative, adsorption positive) antibodies and one sample to be nonspecific reaction to class I antigens, remaining 7 samples were negative to all the wells of EIA identification (id.) kit. Signal/cut-ff (S/C) of all three samples reactive to EIA id. kit were more than 1.75.
CONCLUSIONS
HLA antibody screening by EIA from transplant candidate is considered to be appropriate in that EIA could detect IgG anti-LA of all tested sera and CYNAP antibodies as well. It needs further study with larger number of samples whether S/C of EIA would be informative in cases showing EIA positive/ AHG-DC negative.