MO925VALVULAR HEART DISEASE EVOLUTION IN KIDNEY TRANSPLANT RECIPIENTS AND RELATED RISK FACTORS

Background and Aims

Cardiovascular diseases remains the leading cause of death in recipients of kidney transplantation (KT). Valvular heart disease (VHD) is not an exclusion criteria for KT, however it’s repercussion on KT follow-up has been less studied. Our objective was to analyse the impact of VHD in KT recipients and related risk factors of VHD progression (VHDp).

Method

Observational retrospective cohort study of all patients who underwent KT at Hospital del Mar (Barcelona, Spain) between January 1980 and December 2018. VHD was defined as presence of aortic stenosis (AS), aortic regurgitation, mitral stenosis, mitral regurgitation, tricuspid stenosis, tricuspid regurgitation or double valve injury of any degree diagnosed by echocardiography. We analysed the VHDp, defined as worsening of the initial valvular degree on heart ultrasound after KT, risk factors related with VHDp, recipients and graft survival.

Results

During the study period, 1422 patient underwent KT and 48 of them (3.4%) had VHD diagnosed prior to KT. In the median time of follow-up of 56.3 months (IQR25-75 17.7-119 month), 17 patients (35.4%) presented VHDp and 31 patients did not (64.6%). Figure 1 shows the primary outcome in the different types of VHD, AS was the valve with more VHDp after KT.

Statistical evaluation revealed that recipients with VHDp had a higher body mass index (BMI) (27.4 ± 6.3 vs 24.3 ± 3.8 kg/m2, p=0.04) and worse PTH control (427.0 ± 309.3 vs 186.2 ± 140.6 pg/ml, p=0.02) at the moment of the KT. Also, patients with VHDp reached a worse nadir glomerular filtration rate (GFR) (44.1 ± 17.5 vs 56.0 ± 13.9 ml/min/1.73m2, p=0.01) during the follow-up, needed more time to reach their nadir GFR (4 [2-13] vs 1.2 [1.0-4.7] months, p<0.001) and required more furosemide dose at that time (72.7 ± 21.7 vs 15.8 ± 5.6 mg/day, p=0.02).

At the end of follow-up, 213 KT recipients had died, 16 with preKT-VHD (33.3% of all patients with VHD) and 197 without preKT-VHD (14.3% of all cases without VHD). There was a statistical significant association between preKT-VHD status and all-cause mortality after KT (log rank < 0.001). However, there wasn’t statistical association between preKT-VHD status and death-censored graft survival (log rank = 0.2).

Conclusion

VHD has a significant impact on increased pos-KT mortality but it is not associated with graft survival. More than one third of recipients with preKT-VHD presented deterioration after KT. We found that increased preKT BMI and PTH, nadir GFR after KT, time to reach this nadir GFR and diuretic dose at that time are related with VHD progression.

P1701ANTIBODY MEDIATED REJECTION: CLINICAL PHENOTYPE MATTERS

Background and Aims

Protocol biopsies following kidney transplantation (KT) allow the histological diagnosis of antibody-mediated rejection (ABMR) with stable renal function (RF). Controversy arises when considering isolated proteinuria as a clinical biomarker. Currently, there is no effective treatment for ABMR and transplant units may decide on treatment independently of the clinical expression.

Method

KT recipients (1987-2017) with post-KT biopsies (2008-2018) showing ABMR graft lesions (category 2-Banff’2015) >1year post-KT were included. Cases were grouped into phenotypes of ABMR according to the clinical picture at biopsy : 1) acute RF impairment (↑creatinine >15% three weeks before biopsy) with/without proteinuria and with/without DSA detection. 2) sub-acute RF impairment (↑creatinine >15% six months before biopsy) with/without proteinuria and with/without DSA detection, 3) performed for DSA detection with stable RF and no proteinuria or 4) protocol biopsy, with stable RF, no proteinuria or DSA detection. We considered an additional category: 5) isolated proteinuria (↑>500 mg or x2 six months before biopsy). Categories 1), 2) and 5) were considered clinical ABMR. Categories 3) and 4) were considered subclinical ABMR. We aimed to evaluate graft outcomes in the different ABMR phenotypes.

Results

In a cohort of 105 KT recipients with histologic lesions of ABMR, biopsies corresponded to phenotypes 1) in 35 (33%), 2) 10 (9,5%), 3) 21 (20,3%), 4) 14 (13,4%) and y 5) in 25 23,8%). No differences between clinical and subclinical ABMR were found in baseline characteristics except for donors ‘age, who were older within the clinical group (51.8±18.8 vs. 43.88 ±16.1; p=0.04). At time of biopsy, subclinical had better RF than clinical ABMR (creatinine 1.3±0.4 mg/dl vs. 2.2±1.1 mg/dl; p=0.02) and less proteinuria (161 mg/g [IQR 93-269] vs 939 mg/g [IQR 412-2000]; p=0.001)

Graft survival was worse in those patients with acute and sub-acute RF impairment, followed by those with isolated proteinuria (Figure 1). In comparison to subclinical ABMR, those with RF impairment and isolated proteinuria had an increased risk of graft lost; HR 9.4 (95% IC 2.2-40.7, p=0.002) and 4.8 (95% IC 1.01-23.2, P=0.05) respectively. DSA detection in these groups did not impact graft survival. Specific treatment was not different among groups, except for steroid pulses, which were more frequently applied in cases of ABMR with clinical manifestation.

Conclusion

The clinical phenotypes of ABMR influence long-term graft survival independently from treatment. Understanding graft evolution according to clinical phenotype at the time of histologic diagnosis should guide the therapeutic strategy, to balance risk-benefit ratio.

P1604SIGNIFICANT DETECTION OF UNEXPLAINED HLA ANTIBODIES WITH SINGLE-ANTIGEN BEADS IN PATIENTS ON THE WAITING-LIST WITHOUT PREVIOUS SENSITIZING EVENTS

Background and Aims

The introduction of more sensitive and specific tools as solid phase immunoasssays has improved the ability to detect HLA antibodies. The techniques based on solid phase immunoassays in Luminex system can be performed either as screening assays (with pooled antigen panels that use bead populations coated in affinity-purified class I or class II HLA molecules) or to assess the specificity with single-antigen bead (SAB) assays (single cloned allelic HLA antigen).The sensitivity of each assay Is different, and their results may be discordant. Our objective was to evaluate the potential discrepancies between tests in a cohort of patients on our waiting list with no previous sensitizing events, for their potential influence in the access to transplantation.

Method

Observational study of 184 patients included in the kidney-transplant waiting list on March 31st, 2019. All possible sensitizing events (pregnancy, transfusion and previous transplants) were registered. HLA antibodies where analyzed both by screening and SAB tests.

Results

We limited the observations to males (64.7% of the cohort), as most women (95.4%) had a known sensitizing event, not being possible to discard possible pregnancies in the remaining. Of men, 46.2% had a sensitizing event and 63.8% did not. All 63 unsensitized patients showed a negative screening test, and 49 (77,78%) had at least one SAB done being positive in 73.4% (36/49). The positive SAB yielded a cPRA >10% in 30 cases (between 21-85%), mostly (27/30) due to HLA class II antibodies (88.8% with at least one DQ antibody) with a median MFI of 1571 (range:752-17650).

A thorough review of specificities showed that 81% DQB1* and 89.6% DQA1* antibodies did not show consistency in all beads included for the same allele.

Conclusion

Screening and SAB assays show a significant discordancy in unsensitized men included in the waiting list for kidney transplantation. Automated detection of antibodies by SAB without a proper specialized interpretation may wrongly limit access to transplantation.