Szatmary Peter, Jones James, Hammad Abdul, Middleton Derek
Department of Transplant Surgery , Royal Liverpool University Hospital , Liverpool , UK.
Clin Kidney J. 2013 Jun;6(3):283-6. doi: 10.1093/ckj/sft037.
The clinical relevance of the detection of human leucocyte antigen (HLA) antibodies in sera of renal transplant recipients by highly sensitive methods such as Luminex alone is uncertain and a matter of debate. The choice of output thresholds affects antibody detection and thus organ allocation, yet there are no internationally agreed threshold levels. This study aims at evaluating our current practice of using an MFI threshold of 1000 in antibody detection.
We carried out a case-control study by looking at 761 renal transplant recipients at one unit between 2000 and 2010. Of these, there were 93 cases of graft loss within 1 year and stored serum samples of 40 cases were available for testing. Controls were selected (graft function >2 years) and individually matched according to age, sex, number of transplants and date of transplant. All 40 cases and 40 controls had negative crossmatch by complement-dependent cytotoxicity (CDC) at the time of transplant, and pre-transplant sera were re-analysed for the presence of detectable HLA and donor-specific antibodies (DSAs) using Luminex screen and single-antigen beads and MFI threshold values of 1000, 2000 and 4000.
In nearly 48% of cases with graft loss within a year, HLA antibodies were detectable by Luminex when using a 1000 MFI threshold. This was 25% greater than in controls (P = 0.017). There was also a 15% increase in detected DSAs; however, statistical significance depends on the inclusion or exclusion of one specific case. Using MFI thresholds of 2000 and 4000, no DSAs were found in any long-term surviving grafts.
Selection of appropriate MFI cut-off values influences the detection of DSAs and, thus, organ allocation. Using a threshold of 1000 led to the detection of DSAs in 5% of long-term graft survivors in our population and should be considered too sensitive. Using a detection threshold of 2000 is sufficiently sensitive and leads to clinically relevant detection of DSA.
仅通过诸如Luminex等高灵敏度方法检测肾移植受者血清中的人类白细胞抗原（HLA）抗体的临床相关性尚不确定，存在争议。输出阈值的选择会影响抗体检测，进而影响器官分配，但目前尚无国际公认的阈值水平。本研究旨在评估我们目前在抗体检测中使用1000的平均荧光强度（MFI）阈值的做法。
我们进行了一项病例对照研究，观察了2000年至2010年间一个单位的761名肾移植受者。其中，有93例在1年内移植肾失功，40例的储存血清样本可供检测。选择对照组（移植肾功能>2年），并根据年龄、性别、移植次数和移植日期进行个体匹配。所有40例病例和40例对照在移植时通过补体依赖细胞毒性试验（CDC）交叉配型均为阴性，对移植前血清重新使用Luminex筛选和单抗原微珠分析可检测到的HLA和供者特异性抗体（DSA），MFI阈值分别为1000、2000和4000。
在近48%的1年内移植肾失功的病例中，使用1000的MFI阈值时，通过Luminex可检测到HLA抗体。这比对照组高25%（P = 0.017）。检测到的DSA也增加了15%；然而，统计学意义取决于是否纳入一个特定病例。使用2000和4000的MFI阈值时，在任何长期存活的移植肾中均未发现DSA。
选择合适的MFI截断值会影响DSA的检测，进而影响器官分配。使用1000的阈值导致在我们的研究人群中5%的长期移植肾存活者中检测到DSA，应认为该阈值过于敏感。使用2000的检测阈值足够敏感，可实现与临床相关的DSA检测。
