Department of Clinical Immunology, Medical University of Warsaw, Nowogrodzka 59, 02-006 Warsaw, Poland.
Department of Clinical Immunology, Medical University of Warsaw, Nowogrodzka 59, 02-006 Warsaw, Poland; Department of Immunology, Transplantology and Internal Medicine, Medical University of Warsaw, Nowogrodzka 59, 02-006 Warsaw, Poland.
Transpl Immunol. 2022 Jun;72:101583. doi: 10.1016/j.trim.2022.101583. Epub 2022 Mar 18.
Virtual crossmatch (VXM) is a new powerful tool in pre-transplant risk assessment. However, the ability of VXM to predict physical crossmatch (PXM) results remains controversial. Our work evaluated the predictive potential of VXM results, measured by SAB (single antigen bead assay), for CDCXM (complement-dependent cytotoxicity crossmatch) and FLXM (flow cytometry crossmatch) results of DSA (donor specific antibody) in sensitized patients.
In total, 261 CDCXM and FLXM measurements were performed for 180 potential kidney transplant candidates, each with a single HLA-A, B, or -DR DSA against a potential deceased donor. Analysis was conducted with two SAB datasets of four-month distant and collected prior to and after PXM results. Optimal MFI (mean fluorescence intensity) thresholds and likelihood ratios were assigned based on low (<2000 MFI), medium (2001-5000 MFI) and high risk (>5000 MFI). The impact of VXM predictability was determined by the ROC curves comparison. In addition, inter-assay changes of MFI were evaluated.
The accuracy of VXM to predict CDCXM was inferior to that of FLXM with the AUC (area under ROC curve) of 0.644 vs. 0.849. In contrast, the initial ROC analysis showed that the VXM prediction was good for both T-FLXM with ROC value of 0.849 and by B-FLXM with ROC value of 0.706 for a single antigen of HLA-A, B, or -DR DSA. In fact, the best VXM prediction was for FLXM with good sensitivity for B-FLXM against HLA-DR-specific DSA (0.851). Similar results of VXM predictability were observed for pre- and post-crossmatch ROC curves.
VXM predictability is better for positive/negative FLXM than for positive/negative CDCXM results to evaluate a single HLA-A, B, -DR DSA disparity. This may be related to the fact that VXM and FLXM rely on binding of antibodies to beads or cells, respectively. In contrast, VXM is less predictive for CDCXM because the latter measures complement-dependent cytotoxic function. We intend expand VXM analysis to correlate their results with FLXM results to select low/medium risk patients for kidney transplantation in Poland.
虚拟交叉配型（VXM）是移植前风险评估的新工具。然而，VXM 预测物理交叉配型（PXM）结果的能力仍存在争议。我们的工作评估了 VXM 结果（通过单抗原珠测定法[SAB]测量）对致敏患者的供体特异性抗体（DSA）的 CDCXM（补体依赖性细胞毒性交叉配型）和 FLXM（流式细胞术交叉配型）结果的预测潜力。
总共对 180 名潜在的肾移植候选者进行了 261 次 CDCXM 和 FLXM 测量，每个候选者均具有针对潜在已故供体的单个 HLA-A、B 或-DR DSA。分析使用两个四个月前的 SAB 数据集进行，数据集分别在 PXM 结果之前和之后收集。根据低（<2000 MFI）、中（2001-5000 MFI）和高风险（>5000 MFI），分配了最佳 MFI（平均荧光强度）阈值和似然比。通过 ROC 曲线比较确定 VXM 可预测性的影响。此外，还评估了 MFI 的测定内变化。
VXM 预测 CDCXM 的准确性低于 FLXM，AUC（ROC 曲线下面积）为 0.644 与 0.849。相比之下，初始 ROC 分析表明，对于 T-FLXM（ROC 值为 0.849）和 B-FLXM（对于 HLA-A、B 或-DR DSA 的单个抗原，ROC 值为 0.706），VXM 预测均良好。实际上，对于针对 HLA-DR 特异性 DSA 的 B-FLXM，VXM 对 FLXM 的预测效果最好（0.851）。VXM 可预测性的类似结果也在预交叉配型和后交叉配型的 ROC 曲线中观察到。
VXM 预测性对于阳性/阴性 FLXM 比阳性/阴性 CDCXM 结果更好，以评估单个 HLA-A、B、-DR DSA 差异。这可能与 VXM 和 FLXM 分别依赖于抗体与珠或细胞结合的事实有关。相比之下，VXM 对 CDCXM 的预测性较差，因为后者测量补体依赖性细胞毒性功能。我们打算将 VXM 分析扩展到与 FLXM 结果相关联，以选择波兰的低/中风险患者进行肾移植。
