Background: The Lysate Cross Match (LXM) on Luminex still remains the most commonly prescribed test for pre-transplant donor evaluation in the cost constrained setting. Indiscriminate rejection of the organ donor based on results of LXM test is a possibility. Hence, comparability of results of LXM and Single antigen bead test as well as the clinical significance of the MFI values reported in both the tests needs to be understood properly.
Aim: To assess the comparability and clinical correlation of results of Lysate Cross Match versus Single Antigen Bead (SAB) assay in the pre-transplant setting.
Methods and Material: A retrospective analysis of pre-transplant testing data was performed and seven donor-recipient pairs for which both LXM as well as SAB assay was done were identified. The results of both the tests were compared one to one on the basis of Mean Fluorescence intensity (MFI) values and final interpretation of the test. The outcome of the transplant was noted.
Results: LXM was positive for Class I HLA antibodies in three cases and for Class II HLA antibodies in four cases. MFI values ranged from 1500 to 6500 for Class I and 1000 to 6700 for Class II for LXM test. SAB assay was positive for Class I in three cases and positive for Class II in two cases. The MFI values ranged from 17000 to 21000 for Class I and 5000 to 9000 for Class II for SAB assay. MFI value in SAB assay was found to be 5X and 3.7X the MFI value in LXM assay in case of HLA Class I antibodies and HLA Class II antibodies respectively.. False positive LXM results were noted in two out of seven cases where MFI values for Class II Antibodies were less than 2500. LXM MFI value of 2500 correlated well with positive SAB results in five out of seven cases. 3/7 patients were transplanted and graft survival for mean period of 11 months has been noted.
Conclusion: In cost constraint scenarios where LXM is still utilized for pre-transplant screening and risk stratification, a MFI value of 2500 or above may be considered clinically significant and should be recommended for further testing with the SAB assay. With enhanced immunosuppression regimes, graft survival was achieved in these sensitized cases with very high SAB MFI values.