Sex Differences among Overweight/Obese Kidney Transplant Recipients Requiring Oxygen Support Amid the COVID-19 Pandemic.

Background and Objectives: Overweight/obesity puts individuals at greater risk for COVID-19 progression and mortality. We aimed to evaluate the impact of overweight/obesity on oxygen (O2) requirement outcomes of male and female kidney transplant recipients (KTRs) during the COVID-19 pandemic. Materials and Methods: We conducted a retrospective analysis of a cohort of KTRs diagnosed with COVID-19. Participants were stratified based on BMI categories, and data on the need for O2 therapy outcome were collected and analyzed separately for male and female KTRs. Results: In total, 284 KTRs (97 males and 187 females) were included in the study. Overweight/obesity was observed in 60.6% of male KTRs and 71% of female KTRs. Strikingly, overweight/obese women had a significantly higher requirement for supplemental O2 (63.3% vs. 41.7%, OR = 2.45, p = 0.03), particularly among older individuals (OR = 1.05, p = 0.04), smokers (OR = 4.55, p = 0.03), those with elevated lactate dehydrogenase (LDH) levels (OR = 1.01, p = 0.006), and those with lower admission and basal estimated glomerular filtration rate (eGFR) levels. Within this cohort, the necessity for O2 supplementation was correlated with more unfavorable outcomes. These included heightened mortality rates, transfers to the intensive care unit, employment of invasive mechanical ventilation, and the emergence of acute kidney injury requiring hemodialysis. On the other hand, although overweight/obese male KTRs had a higher prevalence of hypertension and higher fasting blood glucose levels, no significant association was found with COVID-19-related outcomes when compared to lean male KTRs. Conclusions: Overweight/obesity is highly prevalent in KTRs, and overweight/obese women demonstrated a higher need for supplemental O2. Therefore, the early identification of factors that predict a worse outcome in overweight/obese female KTRs affected by COVID-19 contributes to risk stratification and guides therapeutic decisions.

COVID-19 in Kidney Transplant Recipients With Diabetes Mellitus: A Propensity Score Matching Analysis.

Kidney transplant recipients present higher rates of pre-existing comorbidities, in particular diabetes mellitus (DM), hypertension, and cardiac disease. We aimed to verify the main risk factors related to DM that contribute to COVID-19 progression and mortality in a kidney transplant setting. From March to August 2020, we evaluated 300 kidney transplant recipients affected by COVID-19. We used propensity score matching (PSM) to estimate the impact of DM on COVID-19. After matching, all baseline characteristics were well balanced between those with and without DM (n = 100 in each group). Case fatality rate, the requirement of invasive mechanical ventilation (IMV), and acute kidney injury (AKI) were associated with previous fasting blood glucose, and C-reactive protein (CRP), and lactate dehydrogenase (LDH) levels on admission. These findings were similar in kidney transplant patients with and without DM. Glycemia on admission and estimated glomerular filtration rate (eGFR) either on admission or basal correlated to the need of IMV and development of AKI, respectively. Poor glycaemic control, eGFR, markers of inflammation (CRP) and tissue damage (LDH) were indicative of COVID-19 burden in kidney transplant recipients and may be useful tools for risk-stratifying this population, independently of the DM status, during the pandemic.

Lower seroprevalence for SARS-CoV-2-specific antibodies among kidney transplant recipients compared to the general population in the city of Sao Paulo, Brazil.

BACKGROUND: Kidney transplant recipients have higher COVID-19 associated mortality compared to the general population. However, as only symptomatic patients seek medical attention, the current level of exposure, the main sources of acquisition, and the behavior of humoral immunity over time are poorly understood. METHODS: This cross-sectional prospective single-center study recruited kidney transplant recipients of any age living in Sao Paulo. A sample size of 401 patients was calculated considering the 17.2% seroprevalence in the municipality population from a published survey, a 95% confidence interval and an absolute error of 2%. RESULTS: Of the 2636 eligible patients, 416 were included. The seroprevalence for IgG anti-SARS-CoV-2 was 8.2%. Seroconversion rate decreased with increasing age, from 15.7% (18-35 years) to 8.3% (36-60 years) and 4.2% (>60 years, p = 0.042). Seropositivity among previously confirmed COVID-19 patients was 68.4%, followed by 9.4% in those with flu-like symptoms and only 4.6% among asymptomatic patients (p < 0.0001). Seroprevalence was significantly higher among patients reporting household contact (p = 0.018). Twenty-seven from the 34 IgG+ patients had a second test after 59 (IQR 50-63) days, and, in 33%, the IgG index became below the positivity threshold. CONCLUSIONS: In this cohort of kidney transplant recipients, the seroprevalence for IgG anti-SARS-CoV-2 was lower than that of the general population, decreased with ageing, and was associated with household contacts. In a considerable proportion of the patients, there was a significant decay in the IgG levels in a short period of time. Therefore, preventive strategies, such as prioritization for vaccination, should be urgently considered.

Kidney transplantation in the time of COVID-19: Dilemmas, experiences, and perspectives.

INTRODUCTION: Hospital do Rim is a high-volume kidney transplant (KT) center located in São Paulo, a city with 12.2 million inhabitants. Over the last 18 years, we performed 11 436 KT, 70% of which from deceased donors. To mitigate the effects of reduction in the number of transplants on the waiting list, sequential measures were implemented when COVID-19 was declared pandemic. METHODS: The first step was to provide SARS-COV-2 RT-PCR testing for all symptomatic employees and patients and the compulsory use of personal protective equipment in the hospital facilities. Living donor KT were postponed, and all deceased donors and recipients were tested before the transplantation. The immunosuppressive protocols were maintained, and telehealth strategies were developed. RESULTS: Among the 1013 employees, there were 214 cases of COVID-19, nine required ward hospitalization, and no deaths occurred. In 26%, the probable source of contamination was occupational. From the first patient diagnosed with COVID-19 in 03/20/2020 till 10/21/2020, 523 deceased KT were performed, a 21% increase compared with 2019, with no confirmed donor-derived SARS-CoV-2 infection. Four patients were transplanted with a positive pretransplant SARS-CoV-2 test, but none of them developed the disease. Overall, of 11 875 KT followed in our center, 674 developed COVID-19. Among the hospitalized, 53% required mechanical ventilation, and 45% required hemodialysis. Their overall mortality rate was 27.5%. CONCLUSION: This experience shows the challenges that transplant centers faced as the pandemic unfolded and illustrates the effectiveness of the sequential measures implemented to provide a safe environment for transplantation.

Donor-Derived Transmission of Cryptococcus gattii sensu lato in Kidney Transplant Recipients.

We describe cases of donor-derived transmission of Cryptococcus deuterogattii in 2 kidney transplant recipients in Brazil and published information on other cases. Prompt reduction of immunosuppression and initiation of antifungal therapy was required to successfully control the fungal infections and preserve engraftment.

Influence of epidemiology, immunosuppressive regimens, clinical presentation, and treatment on kidney transplant outcomes of patients diagnosed with tuberculosis: A retrospective cohort analysis.

Tuberculosis (TB) mortality is high among kidney transplant (KT) recipients. Although local epidemiology is an important factor, diagnostic/therapeutic challenges and immunosuppressive therapy (ISS) may influence outcomes. We analyzed the cumulative incidence (CumI) of TB in KT recipients receiving a variety of ISS with long-term follow-up. Our retrospective single-center cohort study included all KT procedures performed between January 1, 1998, and August 31, 2014, with follow-up until August 31, 2014. Induction therapy was based on perceived immunological risk; maintenance ISS included prednisone and calcineurin inhibitor (CNI) plus azathioprine (AZA), and mycophenolic acid (MPA) or mechanistic target of rapamycin inhibitor (mTORi). Thirty-four patients received belatacept/MPA. KT was performed on 11 453 patients and followed for 1989 (IQR 932 to 3632) days. Among these, 152 patients were diagnosed with TB (CumI 1.32%). Median time from KT to TB was 18.8 (IQR 7.2 to 60) months, with 59% of patients diagnosed after the first year. Unadjusted analysis revealed an increasing confidence interval (CI) of TB (0.94% CNI/AZA vs 1.6% CNI/MPA [HR = 1.62, 95% CI = 1.13 to 2.34, P = .009] vs 2.85% CNI/mTORi [HR = 2.45, 95% CI = 1.49 to 4.32, P < .001] vs 14.7% belatacept/MPA [HR = 13.14, 95% CI = 5.27 to 32.79, P < .001]). Thirty-seven (24%) patients died, and 39 (25.6%) patients experienced graft loss. Cytomegalovirus infection (P = .02) and definitive ISS discontinuation (P < .001) were associated with death. Rejection (P = .018) and ISS discontinuation (P = .005) occurred with graft loss. TB occurred at any time after KT and was influenced by ISS.

Clinical features and outcomes of kidney transplant recipients with focal segmental glomerulosclerosis recurrence.

AIM: Focal segmental glomerulosclerosis recurs in up to 30% and up to 80% of adult and pediatric kidney transplant recipients, respectively. There is no standard of care treatment. The purpose of this study was to evaluate clinical characteristics, treatments and outcomes of patients with focal segmental glomerulosclerosis recurrence (FSGSr). METHODS: This was a retrospective single-center cohort study including FSGSr patients treated with plasmapheresis (PP) and combinations of high dose steroids, cyclosporine and rituximab. RESULTS: Among 61 patients included in this analysis the median time to diagnosis was 19 days. The incidence of first biopsy-confirmed FSGSr was 18% reaching 52.4% with follow-up biopsies. During PP treatment 54% of the patients developed infectious complications. PP was discontinued in 37% of patients due to treatment failure (no remission or graft loss) and in 26% due to an adverse event. All patients who discontinued PP due to adverse event did not show clinical response or lost the allograft. The incidence of acute rejection was 34.4%. The incidences of partial and complete remissions were 16.4% and 27.8%, respectively. Overall 6-years patient and graft survivals were 90.7% and 64.5%, respectively. CONCLUSION: This analysis confirms the low, variable and unpredictable rate of FSGSr remission, inconsistencies among available therapeutic options and its high rate of adverse events, and the negative impact on graft survival.

Regional differences in the management and outcome of kidney transplantation in patients with human immunodeficiency virus infection: A 3-year retrospective cohort study.

BACKGROUND: In the developed world, kidney transplantation (KT) in patients with human immunodeficiency virus (HIV) infection is well established. Developing countries concentrate 90% of the people living with HIV, but their experience is underreported. Regional differences may affect outcomes. OBJECTIVES: We compared the 3-year outcomes of patients with HIV infection receiving a KT in two different countries, in terms of incomes and development. METHODS: This was an observational, retrospective, double-center study, including all HIV-infected patients >18 years old undergoing KT. RESULTS: Between 2005 and 2015, 54 KTs were performed (39 in a Brazilian center, and 15 in a Spanish center). Brazilians had less hepatitis C virus co-infection (5% vs 27%, P=.024). Median cold ischemia time was higher in Brazil (25 vs 18 hours, P=.001). Biopsy-proven acute rejection (AR) was higher in Brazil (33% vs 13%, P=.187), as were the number of AR episodes (22 vs 4, P=.063). Patient survival at 3 years was 91.3% in Brazil and 100% in Spain; P=.663. All three cases of death in Brazil were a result of bacterial infections within the first year post transplant. At 3 years, survival free from immunosuppressive changes was lower in Brazil (56% vs 90.9%, P=.036). Raltegravir-based treatment to avoid interaction with calcineurin inhibitor was more prevalent in Spain (80% vs 3%; P<.001). HIV infection remained under control in all patients, with undetectable viral load and no opportunistic infections. CONCLUSION: Important regional differences exist in the demographics and management of immunosuppression and antiretroviral therapy. These details may influence AR and infectious complications. Non-AIDS infections leading to early mortality in Brazil deserve special attention.

Prospective Randomized Trial Investigating the Influence of Pharmaceutical Care on the Intra-Individual Variability of Tacrolimus Concentrations Early After Kidney Transplant.

BACKGROUND: This study evaluated the influence of pharmaceutical care (PhC) in the intra-individual variability of dose-corrected whole blood tacrolimus (TAC) trough concentrations, adherence to immunosuppressive therapy and clinical outcomes. METHODS: We randomized 128 kidney transplant recipients to receive PhC consisted of predefined instructions provided by a pharmacist (PhC group, n = 64) or standard nurse staff instructions (control group, n = 64) from day 3 to day 90 after kidney transplantation. The study was powered to detect at least 50% reduction in the coefficient of variation (%CV), calculated from 6 dose-corrected whole blood TAC trough concentrations, in the PhC group. Patient adherence was evaluated using Basel Assessment of Adherence to Immunosuppressive Medication Scale (BAASIS) questionnaire. RESULTS: There was no difference in the %CV comparing PhC and control group (31.4% ± 12.3% versus 32.5% ± 16.1%, P = 0.673). There were no differences in the proportion of patients showing TAC concentrations within predefined target concentrations in each study visit. There was no difference in the proportion of nonadherent patients at day 28 (17% versus 26%, P = 0.135) and day 90 (27% versus 25%, P = 0.457) based on BAASIS questionnaire answers, respectively. There were no differences in clinical outcomes. CONCLUSIONS: Universal PhC in addition to standard nurse staff instruction was not associated with reduced intra-individual variability of dose-corrected whole blood TAC trough concentrations or improved adherence.

Metastasis of skin squamous cell carcinoma in kidney transplant recipients.

Cutaneous squamous cell carcinoma (cSCC) is the most common skin malignancy in kidney transplant recipients (KTRs) as a result of immunosuppression. A worldwide increase in kidney transplantation justifies the determination of prognostic biomarkers by collecting detailed patient data on metastasis development. This study aims to characterize the clinical, epidemiological, and histopathological profiles of KTRs who developed metastasis of cSCC. We conducted a retrospective single-center study on 18 KTRs and 21 immunocompetent patients (ICs) with metastatic cSCC, using data from 2004 to 2021. ICs were older (median age 70.5 years) than KTRs (median age: 59.5 years). Both groups were predominantly male with Fitzpatrick skin phototype I/II. The primary tumor appeared around 83.5 months post-transplant, usually in sun-exposed areas (61.1%), though some non-exposed areas in ICs (23.8%) contradicted literature findings. KTRs took longer to develop metastasis (median: 11.0 months) compared to ICs (median: 5.5 months). The mean size of the primary tumor was smaller in KTRs (2.50 cm2) compared to ICs (4.55 cm2). The main lymph node chain affected by metastasis was parotid lymph nodes in KTRs (27.8%) and cervical/axillar lymph nodes in ICs (both 19.0%). Both groups exhibited similar primary tumor grades and metastasis evolution, but KTRs had a higher prevalence of lymphovascular invasion. Metastasis of cSCC was more common in males with low skin phototype, in KTRs, particularly on the head and neck. The study suggests a possible link between lymphovascular invasion and metastasis development in KTRs.

Oxygen Requirement in Overweight/Obese Kidney Transplant Recipients with COVID-19: An Observational Cohort Study.

INTRODUCTION: Obesity is one of the components of the cardiometabolic syndrome that contributes to COVID-19 progression and mortality. Immunosuppressed individuals are at greater risk of the COVID-19 burden. Therefore, we sought to investigate the impact of the combination of overweight/obesity and kidney transplant on oxygen (O2) requirements in the COVID-19 setting. METHODS: Retrospective analysis of 284 kidney transplant recipients (KTRs) from March/2020 to August/2020 in a single center. We investigated the risk factors associated with O2 requirements in overweight/obese KTRs. RESULTS: Overall, 65.1% had a BMI (body mass index) ≥ 25 kg/m2, 52.4% were male, the mean age was 53.3 ± 11 years old, 78.4% had hypertension, and 41.1% had diabetes mellitus. BMI was an independent risk factor for O2 requirements (OR = 1.07, p = 0.02) alongside age, lymphopenia, and hyponatremia. When overweight/obese KTRs were older, smokers, they presented higher levels of lactate dehydrogenase (LDH), and lower levels of estimated glomerular filtration rate (eGFR), lymphocytes, and sodium at admission, and they needed O2 more often. CONCLUSION: Being overweight/obese is associated with greater O2 requirements in KTRs, in particular in older people and smokers, with worse kidney allograft functions, more inflammation, and lower sodium levels. Therefore, the early identification of factors that predict a worse outcome in overweight/obese KTRs affected by COVID-19 contributes to risk stratification and therapeutic decisions.

Impact of Hypertension on COVID-19 Burden in Kidney Transplant Recipients: An Observational Cohort Study.

BACKGROUND: COVID-19 severity is determined by cardiometabolic risk factors, which can be further aggravated by chronic immunosuppression in kidney transplant recipients (KTRs). We aimed to verify the main risk factors related to hypertension (HTN) that contribute to COVID-19 progression and mortality in that population. METHODS: Retrospective analysis of 300 KTRs from March 2020 to August 2020 in a single center. We compared the main outcomes between HTN (n = 225) and non-HTN (n = 75), including admission to the intensive care unit (ICU), development of acute kidney injury (AKI), need for invasive mechanical ventilation or oxygen, and mortality. RESULTS: Of the patients in the study, 57.3% were male, 61.3% were white, the mean age was 52.5 years, and 75% had HTN. Pre-existing HTN was independently associated with higher rates of mortality (32.9%, OR = 1.96, p = 0.036), transfer to the ICU (50.7%, OR = 1.94, p = 0.017), and AKI with hemodialysis (HD) requirement (40.4%, OR = 2.15, p = 0.011). In the hypertensive group, age, diabetes mellitus, heart disease, smoking, glycemic control before admission, C-reactive protein, lactate dehydrogenase, lymphocytes, and D-dimer were significantly associated with COVID-19 progression and mortality. Both lower basal and previous estimated glomerular filtration rates posed KTRs with HTN at greater risk for HD requirement. CONCLUSIONS: Therefore, the early identification of factors that predict COVID-19 progression and mortality in KTRs affected by COVID-19 contributes to therapeutic decisions, patient flow management, and allocation of resources.

The Full Spectrum of COVID-19 Development and Recovery Among Kidney Transplant Recipients.

BACKGROUND: Coronavirus disease 2019 (COVID-19) fatality rate is high among kidney transplant recipients. Among survivors, kidney outcomes, seroconversion, and persistence of viral shedding are unexplored. METHODS: Single-center prospective cohort study including data from kidney transplant recipients with confirmed COVID-19 between March 20, 2020 and July 31, 2020. Outcomes were adjudicated until August 31, 2020 or the date of death. RESULTS: There were 491 patients with COVID-19 among the 11 875 recipients in follow-up. The majority were middle aged with ≥1 comorbidities. Thirty-one percent were treated at home, and 69% required hospitalization. Among the hospitalized, 61% needed intensive care, 75% presented allograft dysfunction, and 46% needed dialysis. The overall 28-day fatality rate was 22% and among hospitalized patients it was 41%. Age (odds ratio, 3.08; 95% confidence interval, 1.86-5.09), diabetes mellitus (odds ratio, 1.69; 95% confidence interval, 1.06-2.72), and cardiac disease (odds ratio, 2.00; 95% confidence interval, 1.09-3.68) were independent factors for death. Among the 351 survivors, 19% sustained renal graft dysfunction, and there were 13 (4%) graft losses. Biopsy (n = 20) findings were diverse but decisive to guide treatment and estimate prognosis. Seroconversion was observed in 79% of the survivors and was associated with disease severity. Persistence of viral shedding was observed in 21% of the patients without detectable clinical implications. CONCLUSIONS: This prospective cohort analysis confirms the high 28-day fatality rate of COVID-19, associated primarily with age and comorbidities. The high incidence of allograft dysfunction was associated with a wide range of specific histologic lesions and high rates of sequelae and graft loss. Seroconversion was high and the persistence of viral shedding deserves further studies.

The Influence of Antithymocyte Globulin Dose on the Incidence of CMV Infection in High-risk Kidney Transplant Recipients Without Pharmacological Prophylaxis.

BACKGROUND: Optimizing antithymocyte globulin (ATG) dosage is critical, particularly for high-risk kidney transplant (KT) recipients without cytomegalovirus (CMV) prophylaxis. METHODS: We studied 630 KT recipients with expanded criteria donors or panel reactive antibody ≥50% at Hospital do Rim, Brazil (January 1, 2013 to May 21, 2015) to determine whether a single ATG dose was safe and effective in patients without CMV prophylaxis. Patients received ≥4 doses (1-1.5 mg/kg/per dose) until June 17, 2014, when the induction protocol changed to a single ATG dose (3 mg/kg). We used Cox regression to compare the risk of CMV infection and acute rejection (AR) among KT recipients by ATG dose. RESULTS: Adjusting for clinical and transplant factors, a single ATG dose was associated with a lower risk of CMV infection (adjusted hazard ratio [aHR]: 0.63; 95% confidence interval [CI], 0.42-0.93; P = 0.02) and a similar risk of AR (aHR: 1.16; 95% CI, 0.47-2.83; P = 0.8), compared to multiple doses. We found no differences in death-censored graft loss (5.0% versus 4.8%, aHR: 1.06; 95% CI, 0.51-2.23; P = 0.9) or mortality (4.7% versus 3.4%; aHR: 1.42; 95% CI, 0.62-3.24; P = 0.4) at 1-year post-KT by ATG dose. CONCLUSIONS: In our study of high-risk KT recipients without CMV prophylaxis, a single ATG dose decreased the risk of CMV infection without increasing the risk of AR or compromising graft or patient survival.

Clinicopathological characteristics and effect of late acute rejection on renal transplant outcomes.

BACKGROUND: Late acute rejection (LAR) has been associated with inferior kidney allograft outcomes. METHODS: We retrospectively evaluated 355 episodes of biopsy-confirmed LAR in a cohort of 5758 kidney transplants performed between 1998 and 2008. Estimated glomerular filtration rate was obtained before, at, and after each LAR episode as well as histology and treatment. Associations of LAR with subsequent death or graft loss were estimated with Cox proportional regression analysis. RESULTS: A total of 215 patients had 1 episode, 57 had 2 episodes, and 13 had 3 episodes of LAR. Rates of LAR-free survival were 97.4% at 1 year and 93.7% at 5 years. Estimated glomerular filtration rate decreased after each episode of LAR (56±21 vs. 44±18 vs. 36±11 mL/min/1.73 m, P<0.01). The majority of rejections were Banff IA or less, but the chronicity scores as well as plasma cell infiltrates increased after each LAR. All patients requiring dialysis lost their grafts. In a multivariable analysis, the severity of histological score (risk ratio [RR], 3.5; 95% confidence interval [CI], 1.58-7.87; P<0.001), the need for dialysis at LAR (RR, 3.31; 95% CI, 1.44-7.59; P<0.001), and treatment with methylprednisolone (RR, 2.31; 95% CI, 1.07-4.94; P=0.03) were independently associated with graft loss at 5 years, whereas tacrolimus and mycophenolate use was associated with reduced risk (RR, 0.46; 95% CI, 0.25-0.87; P<0.001). CONCLUSIONS: The prevalence and recurrence of LAR are considerable and associated with increased incidence of graft loss. Patients who need dialysis during LAR should be carefully evaluated owing to the high prevalence of graft failure.

Expanding the use of expanded criteria donors in kidney transplantation.

PURPOSE: Although the use of kidney allografts from expanded criteria donors (ECD) has increased in recent years, the reported discard rates are also growing. The influence of ECD characteristics on transplant outcomes is still underevaluated. METHODS: This retrospective study investigated the influence of preimplantation biopsy findings and delayed graft function (DGF) on patient and graft survivals and renal function at 36 months in a cohort of 372 ECD kidney transplant recipients. RESULTS: Patient and graft survivals were 91.6 and 68.9 %. The incidence of biopsy-proven acute rejection was 31 %. There were no differences in patient (88.6 vs. 91.1 vs. 94.7 vs. 78.6 %, p = 0.10) or graft (78.1 vs. 72.2 vs. 60.5 vs. 62.6 %, p = 0.14) survivals and renal function (41.7 ± 25.6 vs. 39.9 ± 29.9 vs. 38.1 ± 30.6 vs. 37.4 ± 29.2 mL/min, p = 0.79) comparing ECD kidneys with mild, moderate, and severe histological changes or with no preimplantation biopsy, respectively. However, severe scored transplants had the worst death-censored graft survival (OR 3.1, 95 % CI 1.4-6.9, p = 0.007). No significant differences in patient (86.2 vs. 83.4 %, p = 0.17) or graft (73.7 vs. 65.9 %, p = 0.06) survivals and renal function (38.9 ± 28.6 vs. 39.9 ± 28.4 mL/min, p = 0.72) were observed comparing patients with or without DGF. Multivariable analysis found diabetes history as the only independent risk factor for graft loss (OR 2.1, 95 % CI 1.3-3.3, p = 0.003) or patient death (OR 3.1, 95 % CI 1.5-5.8, p < 0.001). CONCLUSIONS: Within the limitations of sample size and short follow-up time, in this cohort of ECD kidney transplant recipients the severity of histological changes observed in preimplantation biopsies was independently associated with graft loss.