Division of Transfusion Medicine, Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, Minnesota, USA.
Transfusion. 2021 Nov;61(11):3236-3246. doi: 10.1111/trf.16660. Epub 2021 Sep 15.
Solid-phase platelet crossmatch (PXM) testing is used to help manage patients with platelet transfusion-refractoriness. Recently, we published the first report of false-negative PXM results from prozone effect that was mitigated using sample dilution. This study aimed to describe the prevalence of PXM prozone effect and the levels of class I HLA antibodies (HLA-Abs) associated with positive PXM results and with false-negative PXM results from prozone effect.
A cross-sectional study of patients undergoing PXM testing from July 2019 through December 2020 was performed. All PXM tests were run simultaneously using undiluted and 1:4 diluted patient plasma. Prozone effect was defined as a negative PXM result using undiluted patient plasma but a positive PXM result using 1:4 diluted patient plasma.
Among 59 patients, 830 individual ABO-compatible PXM results yielded an overall positivity rate of 25.8% (214/830) and a false-negative rate from prozone effect of 4.7% (10/214). Among the 28 patients with class I HLA-Ab testing and no other anti-platelet antibodies, maximum HLA-Ab mean fluorescence intensity (MFI) was significantly associated with a positive PXM result (p < .0001; AUC approx. 0.9) and categorized into negative (<3700), indeterminate (3700-10300), and positive (>10300) maximum HLA-Ab MFI zones. Maximum HLA-Ab MFI, however, was not associated with prozone effect (p = .17; AUC approx. 0.6).
While there is a strong predictive association between class I HLA-Ab levels and positive PXM results, PXM prozone effect is a common occurrence not associated with class I HLA-Ab levels, so additional testing with diluted samples should be considered.
固相血小板交叉配型（PXM）检测用于帮助管理血小板输注无效的患者。最近，我们发表了首例由于前带效应导致的 PXM 假阴性结果的报告，该结果可通过样本稀释来缓解。本研究旨在描述 PXM 前带效应的发生率，以及与 PXM 阳性结果和前带效应导致的 PXM 假阴性结果相关的 I 类 HLA 抗体（HLA-Abs）水平。
对 2019 年 7 月至 2020 年 12 月期间进行 PXM 检测的患者进行了横断面研究。所有 PXM 检测均同时使用未稀释和 1:4 稀释的患者血浆进行。前带效应定义为未稀释患者血浆的 PXM 结果为阴性，但 1:4 稀释患者血浆的 PXM 结果为阳性。
在 59 例患者中，830 个单独的 ABO 相容 PXM 结果的总体阳性率为 25.8%（214/830），前带效应导致的假阴性率为 4.7%（10/214）。在 28 例进行 I 类 HLA-Ab 检测且无其他抗血小板抗体的患者中，最大 HLA-Ab 平均荧光强度（MFI）与 PXM 阳性结果显著相关（p<0.0001；AUC 约为 0.9），并分为阴性（<3700）、不确定（3700-10300）和阳性（>10300）最大 HLA-Ab MFI 区。然而，最大 HLA-Ab MFI 与前带效应无关（p=0.17；AUC 约为 0.6）。
虽然 I 类 HLA-Ab 水平与 PXM 阳性结果之间存在很强的预测关联，但 PXM 前带效应是一种常见的现象，与 I 类 HLA-Ab 水平无关，因此应考虑使用稀释样本进行额外的检测。
