Virtual crossmatch in kidney transplantation.

Area of Science:

• Nephrology
• Immunology
• Transplant Surgery

Background:

• Luminex Single-Antigen Beads (LSA) assay detects donor-specific antibodies (DSA) in kidney transplant candidates.
• LSA's sensitivity in detecting low antibody levels complicates accurate crossmatch prediction for donor selection.

Purpose of the Study:

• To retrospectively analyze the accuracy of a virtual crossmatch (v-XM) protocol in predicting actual crossmatch (a-XM) results.
• To investigate the correlation between negative a-XM results and the strength/specificity of preformed DSA.

Main Methods:

• Analyzed correlation between negative v-XMs and a-XMs from 2007-2012.
• Defined 'unacceptable DSA' (MFI≥5,000) and 'acceptable DSA' (MFI<5,000) based on LSA.
• Performed 507 a-XMs using complement-dependent cytotoxicity (CDC) and flow cytometry (FC) on 256 candidates and 302 donors.

Main Results:

• v-XM negative results correlated well with CDC (97%) and FC (90%) a-XMs.
• v-XM demonstrated 100% sensitivity due to no false-negative DSA results.
• Specificity was limited (74% CDC, 79% FC) by 'acceptable' or anti-DQA/DPB DSA.

Conclusions:

• The v-XM protocol exhibits high sensitivity for predicting immunologic compatibility in kidney transplantation.
• Evaluating DSA strength is vital for effective v-XM implementation in recipient selection.
• Accurate v-XM requires defining all donor HLA molecules, especially for anti-DQA/DPB DSA detection.