Impact of low-level donor-specific anti-HLA antibody on post-transplant clinical outcomes of kidney transplant recipients

doi:10.21203/rs.3.rs-1719229/v1

This study aimed to investigate the impact of low-level donor-specific HLA antibody (low-DSA) on post-transplant clinical outcomes of kidney transplantation (KT) recipients. We retrospectively reviewed 1,027 cases of KT, including 629 living donor kidney transplantations (LDKTs) and 398 deceased donor kidney transplantations (DDKTs) between 2010 and 2018 in our center. Low-DSA was confirmed by positive Luminex assay and negative crossmatch test. We compared the incidence of biopsy-proven allograft rejection (BPAR), changes in allograft function, allograft survival, patient survival, and post-transplant infections between subgroups according to pre-transplant low-DSA. The incidence of overall BPAR and T-cell mediated rejection did not differ between subgroups. However, antibody-mediated rejection (ABMR) developed more frequently in patients with low-DSA than in those without low-DSA in the total cohort, LDKT, and DDKT. In multivariate analysis, low-DSA was an independent risk factor for ABMR. Its impact was more pronounced in DDKT (Odds ratio [OR]: 10.000, 95% confidence interval [CI]: 2.781–35.960) than in LDKT (OR: 5.210, 95% CI: 2.100-12.924). There were no significant differences in other outcomes according to low-DSA. In conclusion, pre-transplant low-DSA had a significant impact on the development of AMBR, which was more pronounced in DDKT than in LDKT. However, its impact on long-term outcome was not significant.

The presence of donor-specific anti-human leukocyte antigen (HLA) antibody (HLA-DSA) is an important obstacle for successful transplantation. Positive crossmatch (XM) test due to HLA-DSA has been considered as a very strong risk factor for the development of antibody-mediated rejection (ABMR) and allograft failure^1,2. However, XM test has some limitations to represent the immunologic risk of transplant candidate because this assay presents no quantitative value for HLA-DSA. In addition, it is affected by not only HLA-DSA but also other non-HLA antibodies³.

Meanwhile, Luminex single antigen (LSA) bead assay has been applied in transplantation field. This technique enables us to measure HLA-DSA in a single antigen level with more detailed semi-quantitative value^3–5. Previous studies have shown that mean fluorescence intensity (MFI) value of HLA-DSA presented by LSA assay is significantly correlated with the positivity of XM test⁶. It allows more detailed risk stratification for the risk of ABMR or allograft failure in comparison with traditional XM test^7–9. Therefore, currently used desensitization (DSZ) techniques are based on the MFI value of HLA-DSA in addition to XM test result^10–12. However, when LSA assay is positive and XM test is negative, the clinical relevance of HLA-DSA on post-transplant clinical outcomes remains controversial^13–16. A meta-analysis conducted by Mohan et al.¹⁴ has suggested that preformed low-level HLA-DSA (low-DSA), detected only by LSA assay, increased the risk for ABMR and graft failure. On the other hand, another study performed by Buttigieg et al.¹⁵ has reported that there is no significant difference in acute rejection or graft failure according to the presence of low-DSA.

Based on the above background, the objective of this study was to investigate the impact of low-DSA at baseline on post-transplant clinical outcomes including ABMR and allograft survival in kidney transplantation (KT) recipients. We also analyzed clinical outcomes in living donor kidney transplantation (LDKT) and deceased donor kidney transplantation (DDKT), respectively, to appraise the clinical significance of low-DSA according to donor type.

Baseline characteristics.

Baseline clinical and immunologic characteristics are summarized in Table 1. Of 1,027 KT recipients, 89 (8.7%) had low-DSA. Others were in the no-DSA group. Patients with low-DSA were more likely to be females, to have been transplanted previously, and have higher panel reactive antibody (PRA) values. The follow up period was found to be shorter in the low-DSA group than in the no-DSA group (48.2 months vs. 56.1 months, p = 0.021). The Low-DSA group more frequently received anti-thymocyte globulin (ATG) induction (59.6% vs. 17.1%, p < 0.001) and DSZ therapy (74.2% vs. 12.0%, p < 0.001). On the other hand, most patients (96.7%) initially received triple immunosuppressive therapy containing tacrolimus. There was no difference according to the presence of low-DSA. There were no differences in recipient age, etiology of renal disease, number of HLA mismatches, pre-KT dialysis, donor age, or sex according to the presence of low-DSA. Regarding the donor type, it was observed that the proportion of LDKT in the low-DSA group was significantly higher than that in the no-DSA group (76.4% vs. 59.8%, p = 0.002).

Table 2 shows baseline characteristics of subgroups classified according to low-DSA in LDKT and DDKT, respectively. Among subgroups, 68/629 (10.8%) of LDKT recipients and 21/398 (5.3%) of DDKT recipients had low-DSA. In both LDKT and DDKT, patients in the low-DSA group were more often females, had more frequently previous transplants, and have higher PRA values. There was no difference in low-DSA strength as measured by MFI value between LDKT and DDKT (3675.5 and 4439.5, p = 0.220) (Supplementary Table S1). As in total cohort, the low-DSA group had received ATG more frequently as an induction immunosuppressive therapy (55.9% vs. 3.9%, p < 0.001 in LDKT and 71.4% vs. 36.6%, p = 0.001 in DDKT) and more frequently underwent DSZ therapy (76.4% vs. 13.4%, p < 0.001 in LDKT and 66.7% vs. 9.8%, p < 0.001 in DDKT). There was no difference in initial immunosuppressive agents between subgroups. All DDKT recipients received dialysis prior to transplantation. Dialysis vintage was not different between low-DSA and no-DSA groups. In LDKT, there was no difference in whether dialysis was performed before transplantation according to the presence of low-DSA. However, dialysis vintage was longer in the low-DSA group than in the no-DSA group (36.5 vs. 20.0 months, p = 0.040). Recipient age, etiology of renal disease, number of HLA mismatches, donor age, and sex did not differ according to the presence of low-DSA in either LDKT or DDKT. Additionally, in the low-DSA group, DSZ was performed more frequently for LDKT recipients than for DDKT recipients (76.4% vs. 66.7%, p = 0.003). In terms of the intensity of DSZ, all DDKT recipients (14/21, 66.7%) received rituximab (RTX) alone. However, in LDKT, 26 of 68 (38.2%) recipients received RTX and 26 of 68 (38.2%) took additional Plasmapheresis/intravenous immunoglobulin (PP/IVIG) for DSZ (Supplementary Table S2).

Comparison of overall BPAR and ABMR.

As shown in Fig. 1, the development of overall biopsy-proven allograft rejection (BPAR) was identified in the first year of transplantation, which was divided into T-cell mediated rejection (TCMR) and ABMR. In total cohort, the overall BPAR rate showed no difference between low-DSA and no-DSA groups (p = 0.132). Also, there was no difference of TCMR rate with or without low-DSA (p = 0.155). However, the incidence of ABMR was significantly higher in the low-DSA group than in the no-DSA group (13.5%, 12/89 vs. 2.5%, 23/938, p < 0.001). Multivariable logistic regression analysis was performed to investigate risk factors for the development of ABMR. Predictor variables were tested to ensure that there was no multicollinearity. The presence of low-DSA was found to contribute to models, with odds ratio (OR) of 6.281 (95% confidence interval [CI] 3.009–13.115, p < 0.001) (Table 3).

Similar results were also observed in subgroup analysis. The overall BPAR rate did not differ between low-DSA and no-DSA groups in LDKT (p = 0.405) or DDKT (p = 0.116). TCMR rate was not different according to the baseline low-DSA in LDKT (p = 0.150) or DDKT (p = 1.000) either (Fig. 1). On the other hand, ABMR developed more frequently in the low-DSA group than in the no-DSA group in both LDKT (11.8%, 8/68 vs. 2.5%, 14/561, p = 0.001) and DDKT (19%, 4/21 vs. 2.4%, 9/377, p = 0.003). The multivariable logistic analysis revealed that the impact of low-DSA on the development of ABMR was greater in DDKT than in LDKT (OR: 10.000, 95% CI: 2.781–35.960, p < 0.001 vs. OR: 5.210, 95% CI: 2.100-12.924, p < 0.001) (Table 3).

Comparison of changes in allograft function, allograft failure, and patient survival.

Allograft function did not differ between low-DSA and no-DSA groups in total cohort, LDKT, or DDKT until 36 months after KT (Fig. 2). During follow-up period, there were a total of 74 cases (74/1027, 7.2%) of death-censored graft failure: 3 cases (3/89, 3.4%) in the low-DSA group and 71 cases (71/938, 7.6%) in the no-DSA group. According to the donor type, there were 33 allograft failures in LDKT: 1 case (1/68, 1.5%) in the low-DSA group and 32 cases (32/561, 5.7%) in the no-DSA group. There were 41 allograft failures in DDKT: 2 cases (2/21, 9.5%) in the low-DSA group and 39 cases (39/377, 10.3%) in the no-DSA group. No significant difference in death-censored allograft survival rate according to the presence of low-DSA was observed in total cohort, LDKT, or DDKT (Fig. 3). Among patients who experienced ABMR in the first year of transplantation, 1 of 12 low-DSA and 8 of 23 no-DSA patients eventually lost their graft function. Treatment of ABMR was performed according to clinical decision, including steroid pulse, PP and IVIG, RTX, and bortezomib. Rejection was the leading cause of allograft failure, with the exception of one patient who lost his graft due to BK polyomavirus-associated nephropathy (BKPyAN) (Supplementary Tables S3, S4). A total of 48 patients (48/1027, 4.7%) died, of them only one patient with low-DSA died by suicide. There was no significant difference in patient survival rate according to the presence of low-DSA in total cohort or LDKT (Fig. 4). Since there was no patient death in the DDKT group, statistical analysis could not be performed.

Comparison of post-transplant infections.

A total of 567 cases (567/1027, 55.2%) of infectious complications developed during the follow-up period. The incidence of BK virus (BKV) infection was higher in the low-DSA group than in the no-DSA group of LDKT (23.6%, 16/68 vs. 13.4%, 75/561, p = 0.024). Incidences of overall infection and other type of infections were not significantly different between the two groups in total cohort, LDKT, or DDKT (Supplementary Table S5). In LDKT, there was a significant difference in infection-free survival rate between low-DSA and no-DSA groups (p = 0.041). However, this difference was not observed in the total cohort or DDKT (Supplementary Figure S1). Supplementary Table S6 details univariable and multivariable Cox regression analysis results predicting post-transplant infections. ATG induction was an independent predictor for post-transplant infections in both LDKT (Hazard ratio [HR]: 1.453, 95% CI: 1.012–2.086, p = 0.043) and DDKT (HR: 1.585, 95% CI: 1.224–2.054, p < 0.001). Patient female sex was an additional predictor in LDKT (HR: 1.391, 95% CI: 1.108–1.746, p = 0.004). Neither low-DSA nor DSZ was identified as a predictor of post-transplant infection using Cox regression models.

This study showed that pre-transplant low-DSA was a significant risk factor for ABMR. However, this impact did not lead to difference in long-term allograft outcome such as changes of allograft function, allograft, or patient survival rate. The same results were confirmed in subgroup analysis according to donor type. The impact of low-DSA on ABMR was less significant in LDKT than in DDKT. It might be because of the more frequent application of DSZ in LDKT. At the same time, DSZ did not increase the risk of post-transplant infection significantly.

First, we compared the incidence of BPAR according to the presence of pre-transplant low-DSA. We found that low-DSA was associated with the development of ABMR in both LDKT and DDKT. There was no such association for overall BPAR and TCMR. This result corresponds well with previous studies^6,17,18. When we confirmed risk factors for AMBR, low-DSA was a significant predictor in both LDKT and DDKT. Its impact was more pronounced in DDKT than in LDKT. We corrected in a multivariable analysis to determine the impact of low-DSA on ABMR for confounding factors such as donor type, donor age, DSZ therapy, ATG induction, patient age, and cold ischemic time (CIT) only in DDKT. In the final model, there were no significant predictors of ABMR except for low-DSA. It is well known that allograft outcomes are worse in DDKT than in LDKT^19,20. It is possibly due to the poor organ quality in brain-dead donors, which is associated with prolonged CIT, cardiovascular instability, and use of vasopressors during organ procurement²¹. Adhesion molecules and HLA antigens are likely to be highly expressed in brain-dead donor kidneys than in living donor kidneys²². They can lead to an increase in the incidence of acute ABMR. In this study, the age of deceased donors was significantly older than that of living donors, which might have contributed in part to the poor organ quality.

Another possible reason for the less significant impact of low-DSA on the development of ABMR in LDKT could be associated with the more frequent application of DSZ in the LDKT subgroup. A previous study showed that DSZ therapy in patients with low-DSA could reduce the incidence of ABMR²³. In addition, it is suspected that differences in DSZ protocols can be associated with discrepancy in the impact of low-DSA on clinical outcomes between studies ^17,18. Based on these background, we also conducted DSZ treatments in patients with low-DSA at baseline in LDKT. The application of these DSZs to DDKT was difficult because we did not have enough time to conduct DSZ before KT. It was crucial to minimize total ischemic time in order to preserve the quality of donor kidney in DDKT. Indeed, DSZ was performed more frequently in LDKT than in DDKT for the low-DSA group (76.4% vs. 66.7%). Moreover, the intensity of DSZ was stronger in LDKT than in DDKT. All DDKT recipients who underwent DSZ received RTX alone. However, in LDKT, half of desensitized patients additionally took PP/IVIG. Taken together, it is possible that a more pronounced impact of preformed low-DSA on ABMR in DDKT can result from less intensified DSZ than in LDKT.

Next, we investigated long-term allograft outcomes. In contrast to the finding that low-DSA affected the development of acute ABMR, there was no significant difference in allograft function changes according to the presence of low-DSA during the 36-month observation period. Furthermore, allograft and patient survival were not associated with the presence of low-DSA. In this study, death-censored graft survival rate of the low-DSA group was 96.6%, which was significantly superior to those of previous studies^5,6,24−26. In the low-DSA group, only one patient who experienced ABMR in the first year of KT lost his graft function. These favorable long-term allograft outcomes can be explained by the effect of aggressive DSZ protocol in our cohort, considering that compared to de novo HLA-DSA, pre-existing HLA-DSA was less likely to cause allograft failure if aggressive immunosuppression was performed ²⁷.

There may be concerns that DSZ can increase the risk for infectious complications. As DSZ protocols are basically based on the elimination or reduction of preformed antibodies prior to transplantation²⁸, over-immunosuppression caused by DSZ could increase infection rate after KT^29,30. In this study, the low-DSA group received more intense DSZ in LDKT than in DDKT as previously mentioned. For this reason, we analyzed the association between pre-transplant low-DSA and post-transplant infections. In LDKT, BKV infection was more common and infection-free survival was inferior in the low-DSA group that in the no-DSA group. However, we could not identify neither pre-existing low-DSA nor DSZ as a significant predictor for post-transplant infections using Cox regression models. Instead, ATG induction was identified as an independent predictor in both LDKT and DDKT, and patient female sex was an additional predictor in LDKT. Meanwhile, in DDKT, there was no difference in the incidence of infectious complications according to the presence of low-DSA. Only ATG induction, not low-DSA or DSZ, was identified as an independent risk factor for post-transplant infections. Unlike patients with strong HLA-DSA³¹, relatively weak DSZ was applied to patients with low-DSA, which did not increase the risk of post-transplant infection in this study.

This study has some limitations. First, this was a single-center study with a small number of patients who had performed low-DSA. Therefore, a large multicenter study with a long observation period is needed. Nevertheless, our study had a strength in that we were able to predict and control effects of immunosuppression more precisely since there was a unified immunosuppression protocol for DSZ, induction, and maintenance immunosuppression.

In conclusion, pre-transplant low-DSA had a prominent impact on the development of ABMR. However, the impact on the long-term allograft outcomes and post-transplant infections was limited. The impact of low-DSA on ABMR was more significant in DDKT than in LDKT. One possible reason might be because more intensified DSZ was available in LDKT. Therefore, we recommend DSZ, if possible, in patients with low-DSA to decrease the risk for ABMR in both LDKT and DDKT.

Study population.

Between January 2010 and December 2018, 1,284 cases of KT were performed in Seoul St. Mary’s Hospital (Seoul, Korea). Patients with positive XM test, pediatric patients (< 18 years), patients receiving ABO incompatible transplants, and patients who received concurrent kidney and other solid organ or hematopoietic stem cell transplantation were excluded. Therefore, we included 1,027 kidney transplants (LDKT: 629 cases, DDKT: 398 cases). Patients whose HLA-DSA was positive in LSA assay (MFI > 1,000) but negative in XM test were defined as a low-DSA group. Patients without HLA-DSA in both LSA assay and XM test were defined as a no-DSA group. Negative XM test was confirmed by both complement-dependent cytotoxicity crossmatch (CDC-XM) and flow cytometry crossmatch (FCXM) methods. As a result, of 1,027 patients, 89 had low-DSA, including 68 who received LDKT and 21 who received DDKT. Finally, there were 68 low-DSA and 561 no-DSA patients in LDKT and 21 low-DSA and 377 no-DSA patients in DDKT (Figure. 5). The median follow-up period of this study was 53.5 (interquartile range: 30.1–82.1) months. This study was performed in accordance with the Declaration of Helsinki and the Declaration of Istanbul. The study was approved by the Institutional Review Board of Seoul St. Mary’s Hospital (KC22RISI0380). The requirement for informed consent from participants was waived by the institutional review board of the Catholic University of Korea due to the retrospective study design and non-invasive procedures.

Detection and definition of HLA-DSA.

Our center’s immunologic work up protocol was presented previously³². Briefly, we performed PRA screening and XM tests using both CDC-XM and FCXM as a baseline immunologic test. In patients with positive PRA screening result (> 20%) or positive result of XM test, we investigated the presence of HLA-DSA using LSA assay. PRA screening test was done with the Luminex method (LABScreen™ mixed class I and II; One Lambda, Inc.; Canoga Park, CA, USA). It was presented as %PRA. CDC-XM and FCXM tests were performed in the standard manner^33,34. LSA assay for HLA-DSA was performed according to the manufacturer’s instructions, using LABScreen™ single antigen HLA class I - combi and class II - group 1 kits (One Lambda, Inc). The positive criterion was an MFI level > 1,000. In all patients and donors, HLA typing was performed using LIFECODES HLA-A, B, C, DRB1, DQB1 SSO Typing Kit (Immucor Transplant Diagnostics, Ic. 550 West Avenue, Stamford, CT, USA 06902). This procedure was based on the hybridization of labeled single stranded PCR product to SSO probes. If the LSA assay-detected anti-HLA antibody in the patient corresponded to the HLA type of the donor, it was classified as an HLA-DSA.

Pre-transplant DSZ protocol.

Our center’s DSZ protocol has been presented previously ^12,32,35. Briefly, we used stratified protocol according to the baseline MFI value. The target of DSZ in our center was negative conversion of XM result in XM positive patients and reduction of HLA-DSA MFI level below 5,000. DSZ strategy for patients with low-DSA was dependent on the baseline MFI value. In patients who had MFI value over 5,000, RTX at a dose of 375 mg/m2 (MabTheraTM; Genentech, Inc., San Francisco, CA, USA) was administered 2–3 weeks before transplantation. PP/IVIG therapy was initiated 7 days prior to transplantation and administered every other day. In addition, we initiated immunosuppressant treatment two days prior to transplantation in these patients. On the other hand, in patients with MFI value below 5,000, DSZ was performed using RTX at a dose of 375 mg/m² in case where the PRA screening results were > 50%. PP was performed using a COBE Spectra apheresis system (Gambro BCT Inc., Lakewood, CO, USA)³⁶. At each PP session, one plasma volume was removed and replaced with either a 5% albumin solution or fresh frozen plasma. Intravenous immunoglobulin (100–200 mg/kg) was infused 1 h after each PP session.

Definition of clinical outcomes.

The primary outcome of this study was the incidence of BPAR. Secondary outcomes were changes in allograft function measured as estimated glomerular filtration rate (eGFR), death-censored allograft survival rate, patient survival rate, and post-transplant infection rate. Allograft rejection was diagnosed and classified as ABMR and TCMR according to Banff 2017 criteria³⁷. Serum creatinine levels were collected at 3, 6, 12, 24, and 36 months after transplantation. The eGFR for each concordant time was assessed using the chronic kidney disease-epidemiology collaboration (CKD-EPI) Eq. 3⁸. Graft failure was defined as a return to dialysis dependence or retransplantation. In the analysis of death-censored graft failure, patients who died with a functioning graft were censored at the time of death. Infection episode was defined as the occurrence of an infectious event requiring hospitalization. Cytomegalovirus (CMV) infection was defined as CMV DNAemia and/or any kind of organ involvement due to CMV³⁹. BKV infection was defined as the BKV DNAemia with DNA titer ≥ 10⁴ copies/ml and/or biopsy-proven BKPyAN⁴⁰. Infection-free graft survival was defined as the time from transplantation to the first infection episode.

Statistical analysis.

Categorical variables are presented as counts and percentages. They were analyzed by Pearson’s chi-square test or Fisher’s exact test, as appropriate. Continuous variables with normal distribution are expressed as mean ± standard deviation. They were analyzed by two-sample t test. Continuous variables with non-normal distribution are expressed as median with interquartile range. They were analyzed by the Mann-Whitney U test. Survival curves were generated by the Kaplan-Meier method. Groups were compared using the log-rank test. Predictors of the ABMR were explored with multivariable logistic regression analysis. Clinical parameters showing significant differences (p-value < 0.05) in univariable analysis or known to cause ABMR were fitted into the multivariable model. We selected donor type, donor age, CIT (only in DDKT), pre-transplant low-DSA, DSZ, ATG induction, and patient age as predictors. Multivariable Cox regression analyses with backward selection were used to investigate independent predictors for infectious episodes. Cox models were built considering patient age, sex, CIT (only in DDKT), pre-transplant low-DSA, DSZ, and ATG induction. Linear mixed model was performed to compare changes in allograft function over time. All missing data were censored from the last follow-up date. For all tests, a two-tailed p-value < 0.05 was considered to indicate statistical significance. All data were analyzed using SPSS® software, version 24 (IBM Corporation, Armonk, NY, USA). In addition, all graphs were generated using Prism software (GraphPad, San Diego, CA, USA).

ABMR antibody-mediated rejection

ATG anti-thymocyte globulin

BKV BK virus

BKPyAN biopsy-proven BK polyomavirus-associated nephropathy

BPAR biopsy-proven allograft rejection

CDC-XM complement-dependent cytotoxicity crossmatch

CI confidence interval

CIT cold ischemic time

CKD-EPI chronic kidney disease-epidemiology collaboration

CMV cytomegalovirus

DDKT deceased donor kidney transplantation

DSA donor-specific antibody

DSZ desensitization

eGFR estimated glomerular filtration rate

FCXM flow cytometry crossmatch

HLA human leukocyte antigen

HLA-DSA donor-specific anti-HLA antibody

HR hazard ratio

IST immunosuppresant

IVIG intravenous immunoglobulin

KT kidney transplantation

LDKT living donor kidney transplantation

Low-DSA low level donor-specific anti-HLA antibody

LSA luminex single antigen

MFI mean fluorescence intensity

OR odds ratio

PP plasmapheresis

PRA panel reactive antibody

RTX rituximab

TCMR T-cell mediated rejection

XM crossmatch

Acknowledgements

This study was supported by a grant from the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI22C0422) and research grant from the Korean Society for Transplantation and by Research Fund of Seoul St. Mary’s Hospital, The Catholic University of Korea.

Author contributions

H.L.¹: participated in designing study, analyzing and interpreting the data, preparing figures and tables, and writing the paper. H.L.², S.H.E., E.J.K., J.-W.M., E.-J.O.: participated in collecting data. C.W.Y: participated in analyzing the data. B.H.C.: participated in designing study, analyzing and interpreting the data, and revising the paper. All authors read and approved the final manuscript.

HL¹: Haeun Lee, HL²: Hanbi Lee

Competing interests

The authors declare no competing interests

Correspondence and requests for materials should be addressed to B.H.C.

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Table 1. Baseline characteristics stratified according to the presence of low-DSA

Characteristics	Low-DSA (n=89)	No-DSA (n=938)	P value
Patients
Age (years)	48.6 ± 10.7	47.3 ± 11.3	0.322
Female sex (n, %)	61 (68.5)	354 (37.7)	< 0.001
Etiology of renal disease (n, %)			0.395
Diabetes	19 (21.3)	206 (22.0)
Hypertension	8 (9.0)	132 (14.1)
Glomerulonephritis	38 (42.7)	329 (35.1)
Others	24 (27.0)	271 (28.9)
HLA-A/B/DR mismatches	3.4 ± 1.3	3.2 ± 1.7	0.215
PRA ∣ (%)	47.7 ± 41.3	9.5 ± 24.7	< 0.001
PRA∥(%)	39.9 ± 43.5	10.5 ± 25.2	< 0.001
PRA >50% (n, %)	67 (75.3)	149 (15.9)	< 0.001
Pre-transplant dialysis (n, %)	68 (76.4)	749 (79.9)	0.441
Time on dialysis (months)	45.0 ± 60.8	43.7 ± 56.7	0.829
Follow up period (months)	48.2 ± 30.7	56.1 ± 30.5	0.021
Donors
Age (years)	43.0 ± 12.7	44.8 ± 13.0	0.207
Female sex (n, %)	38 (42.7)	448 (47.8)	0.360
Living donor (n, %)	68 (76.4)	561 (59.8)	0.002
Transplants
Retransplant (n, %)	24 (27.0)	73 (7.8)	< 0.001
Induction therapy (n, %)			< 0.001
Basiliximab	36 (40.4)	778 (82.9)
ATG	53 (59.6)	160 (17.1)
Initial immunosuppression (n, %)			0.353
Tacrolimus	88 (98.9)	905 (96.5)
Cyclosporine	1 (1.1)	33 (3.5)
Desensitization (n, %)			< 0.001
No, n	23 (25.8)	825 (88.0)
Yes, n	66 (74.2)	113 (12.0)

Continuous variables are shown as mean ± standard deviation. Categorical variables are shown as number (proportions). ATG, anti-thymocyte globulin; HLA, human leukocyte antigen; Low-DSA, low level donor-specific anti-HLA antibody; PRA, panel-reactive antibody.

Table 2. Baseline characteristics with LDKT and DDKT stratified according to the presence of low-DSA

Characteristics	LDKT (n=629)		P value	DDKT (n=398)		P value
	Low-DSA (n=68)	No-DSA (n=561)		Low-DSA (n=21)	No-DSA (n=377)
Patients
Age (years)	47.0 ± 10.8	45.6 ± 12.0	0.317	53.7 ± 8.8	49.9 ± 9.6	0.080
Female sex (n, %)	47 (69.1)	207 (36.9)	< 0.001	14 (66.7)	147 (39.0)	0.012
Etiology of renal disease (n, %)			0.673			0.866
Diabetes	14 (20.6)	128 (22.8)		5 (23.8)	78 (20.7)
Hypertension	5 (7.4)	52 (9.3)		3 (14.3)	80 (21.2)
Glomerulonephritis	30 (44.1)	205 (36.5)		8 (38.1)	124 (32.9)
Others	19 (27.9)	176 (31.4)		5 (23.8)	95 (25.2)
HLA-A/B/DR mismatches	3.3 ± 1.3	3.0 ± 1.7	0.260	4.0 ± 1.0	3.6 ± 1.5	0.264
PRA ∣ (%)	66.8 ± 32.9	50.6 ± 34.9	0.007	73.9 ± 28.5	52.9 ± 32.7	0.028
PRA∥(%)	76.0 ± 26.5	55.4 ± 31.3	0.001	80.4 ± 31.4	51.3 ± 29.5	0.002
PRA >50% (n, %)	51 (75.0)	88 (15.7)	< 0.001	16 (76.2)	61 (16.2)	< 0.001
HLA-DSA peak MFI	3675.5 (1903.0-6213.0)	n.a	n.a	4439.5 (2556.0-8728.0)	n.a	n.a
Pre-transplant dialysis (n, %)	47 (69.1)	372 (66.3)	0.643	21 (100.0)	377 (100.0)	n.a
Time on dialysis (months)	36.5 ± 52.0	20.0 ± 38.7	0.040	109.1 ± 58.4	88.8 ± 54.7	0.100
Follow up period (months)	47.7 ± 31.8	55.6 ± 31.6	0.051	50.0 ± 27.4	56.7 ± 28.7	0.295
Donors
Age (years)	41.4 ± 12.5	43.3 ± 12.2	0.211	53.7 ± 8.8	49.9 ± 9.6	0.080
Female sex (n, %)	32 (47.1)	320 (57.0)	0.117	5 (28.6)	128 (34.0)	0.612
Transplants
Retransplant (n, %)	15 (22.1)	45 (8.0)	< 0.001	9 (42.9)	28 (7.4)	< 0.001
Induction therapy (n, %)			< 0.001			0.001
Basiliximab	30 (44.1)	539 (96.1)		6 (28.6)	239 (63.4)
ATG	38 (55.9)	22 (3.9)		15 (71.4)	138 (36.6)
Initial immunosuppression (n, %)			0.236			1.000
Tacrolimus	67 (98.5)	532 (94.8)		21 (100.0)	373 (98.9)
Cyclosporine	1 (1.5)	29 (5.2)		0 (0.0)	4 (1.1)
Desensitization (n, %)			< 0.001			< 0.001
No	16 (23.5)	486 (86.6)		7 (33.3)	340 (90.2)
Yes	52 (76.4)	75 (13.4)		14 (66.7)	37 (9.8)

Continuous variables are shown as mean ± standard deviation or median with interquartile range. Categorical variables are shown as number (proportions). ATG, anti-thymocyte globulin; DDKT, deceased donor kidney transplantation; HLA, human leukocyte antigen; HLA-DSA, donor-specific anti-HLA antibody; LDKT, living donor kidney transplantation; Low-DSA, low level donor-specific anti-HLA antibody; MFI, mean fluorescence intensity; PRA, panel-reactive antibody.

Table 3. Prediction of the biopsy-proven ABMR within one year of transplantation

Total cohort	β coefficient	Standard error	Odds ratio (95% CI)	p-value
Total cohort	β coefficient	Standard error	Odds ratio (95% CI)	p-value
Low-DSA	1.838	0.376	6.281 (3.009-13.115)	< 0.001
LDKT
Low-DSA	1.650	0.464	5.210 (2.100-12.924)	< 0.001
DDKT
Patient age	-0.056	0.030	0.946 (0.891-1.004)	0.066
Low-DSA	2.303	0.653	10.000 (2.781-35.960)	< 0.001

CI, confidence interval; DDKT, deceased donor kidney transplantation; LDKT, living donor kidney transplantation; Low-DSA, low level donor specific anti-HLA antibody.

No competing interests reported.

LeeetalImpactoflowDSASciRsuppl.pdf

Impact of low-level donor-specific anti-HLA antibody on post-transplant clinical outcomes of kidney transplant recipients

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Abstract

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Statistical analysis.

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