The Strategies Used to Balance Health and Work Across the Solid Organ Transplantation Trajectory

Introduction: Workers who undergo solid organ transplantation report frequent conflicts between the unpredictable demands of their health condition and the rigid requirements of their employer and of health services. The present study aimed to describe the self-management strategies adopted by workers while staying at work before transplantation and during sustainable return-to-work posttransplantation. Methods: Fifteen employed kidney, liver, and lung transplant recipients were recruited from 2 large urban university health centers in Montreal, Canada. Three focus groups were held, and thematic analysis was performed. Findings: Seven strategies were identified: responding promptly and consistently to fatigue-related needs, planning ahead with immediate supervisors while remaining strategic about when to disclose transplantation, requesting work accommodations, requesting flexibility in healthcare provision, consulting physicians about work-related issues, informing co-workers about work limitations and immunosuppression and asking not to be treated differently in the workplace. Conclusion: Access to work accommodations, support from physicians and flexibility in treatment and appointment schedules supported workers' ability to manage their health while staying at work before and after undergoing solid organ transplantation. In light of findings, it may be useful for healthcare professionals to address workers' concerns about work limitations and work accommodation implementation, especially when the illness-management burden increases before transplantation and during posttransplantation sick leave. Future studies could describe the strategies used by other important stakeholders when attempting to provide support to workers.

Differences in excess mortality by recipient sex after heart transplant: An individual patient data meta-analysis

BACKGROUND

Identification of differences in mortality risk between female and male heart transplant recipients may prompt sex-specific management strategies. Because worldwide, males of all ages have higher absolute mortality rates than females, we aimed to compare the excess risk of mortality (risk above the general population) in female vs male heart transplant recipients.

METHODS

We used relative survival models conducted separately in SRTR and CTS cohorts from 1988-2019, and subsequently combined using 2-stage individual patient data meta-analysis, to compare the excess risk of mortality in female vs male first heart transplant recipients, accounting for the modifying effects of donor sex and recipient current age.

RESULTS

We analyzed 108,918 patients. When the donor was male, female recipients 0-12 years (Relative excess risk (RER) 1.13, 95% CI 1.00-1.26), 13-44 years (RER 1.17, 95% CI 1.10-1.25), and ≥45 years (RER 1.14, 95% CI 1.02-1.27) showed higher excess mortality risks than male recipients of the same age. When the donor was female, only female recipients 13-44 years showed higher excess risks of mortality than males (RER 1.09, 95% CI 1.00-1.20), though not significantly (p = 0.05).

CONCLUSIONS

In the setting of a male donor, female recipients of all ages had significantly higher excess mortality than males. When the donor was female, female recipients of reproductive age had higher excess risks of mortality than male recipients of the same age, though this was not statistically significant. Further investigation is required to determine the reasons underlying these differences.

A Multinational Cohort Study Examining Sex Differences in Excess Risk of Death With Graft Function After Kidney Transplant

BACKGROUND

Kidney transplant recipients show sex differences in excess overall mortality risk that vary by donor sex and recipient age. However, whether the excess risk of death with graft function (DWGF) differs by recipient sex is unknown.

METHODS

In this study, we combined data from 3 of the largest transplant registries worldwide (Scientific Registry of Transplant Recipient, Australia and New Zealand Dialysis and Transplant Registry, and Collaborative Transplant Study) using individual patient data meta-analysis to compare the excess risk of DWGF between male and female recipients of a first deceased donor kidney transplant (1988-2019), conditional on donor sex and recipient age.

RESULTS

Among 463 895 individuals examined, when the donor was male, female recipients aged 0 to 12 y experienced a higher excess risk of DWGF than male recipients (relative excess risk 1.68; 95% confidence interval, 1.24-2.29); there were no significant differences in other age intervals or at any age when the donor was female. There was no statistically significant between-cohort heterogeneity.

CONCLUSIONS

Given the lack of sex differences in the excess risk of DWGF (other than in prepubertal recipients of a male donor kidney) and the known greater excess overall mortality risk for female recipients compared with male recipients in the setting of a male donor, future study is required to characterize potential sex-specific causes of death after graft loss.

Predicting Long-term Outcomes in Deceased Donor Kidney Transplant Recipients Using Three Short-term Graft Characteristics

Key Points

Delayed graft function is not an ideal measure of graft function, yet is used to assess risk in kidney transplantation. We propose a model that combines it with two other measures of 90-day graft function to identify recipients at incremental risk of inferior long-term outcomes.

Background

Delayed graft function (DGF) in kidney transplant recipients is used to determine graft prognosis, make organ utilization decisions, and as an important end point in clinical trials. However, DGF is not an ideal measure of graft function. We aimed to develop and validate a model that provides incremental risk assessment for inferior patient and graft outcomes.

Methods

We included adult kidney-only deceased donor transplant recipients from 1996 to 2016. In addition to DGF, two short-term measures were used to assess risk: renal function recovery <100% (attaining half the donor's eGFR) and recipient's 90-day eGFR <30. Recipients were at no, low, moderate, or high risk if they met zero, one, two, or all criteria, respectively. Cox proportional hazard models were used to assess the independent relationship between exposure and death-censored graft failure (DCGF) and mortality.

Results

Of the 792 eligible recipients, 24.5% experienced DGF, 40.5% had renal function recovery <100%, and 6.9% had eGFR <30. Over a median follow-up of 7.3 years, the rate of DCGF was 18.7% and mortality was 25.1%. When compared with recipients at no risk, those at low, moderate, and high risk were noted to have an increase in risk of DCGF (adjusted hazard ratio [aHR], 1.53; 95% confidence interval [CI], 1.03 to 2.27; aHR, 2.84; 95% CI, 1.68 to 4.79; aHR, 15.46; 95% CI, 8.04 to 29.71) and mortality (aHR, 1.16; 95% CI, 0.84 to 1.58; aHR, 1.85; 95% CI, 1.13 to 3.07; aHR, 2.66; 95% CI, 1.19 to 5.97). When using a hierarchical approach, each additional exposure predicted the risk of DCGF better than DGF alone and 100 random bootstrap replications supported the internal validity of the risk model. In an external validation cohort deemed to be at lower risk of DCGF, similar nonsignificant trends were noted.

Conclusion

We propose a risk model that provides an incremental assessment of recipients at higher risk of adverse long-term outcomes than DGF alone. This can help advance the field of risk assessment in transplantation and inform therapeutic decision making in patients at the highest spectrum of inferior outcomes.

A multinational cohort study uncovered sex differences in excess mortality after kidney transplant

Worldwide and at all ages, males have a higher mortality risk than females. This mortality bias should be preserved in kidney transplant recipients unless there are sex differences in the effects of transplantation. Here we compared the excess risk of mortality (risk above the general population) in female versus male recipients of all ages recorded in three large transplant databases. This included first deceased donor kidney transplant recipients and accounted for the modifying effects of donor sex and recipient age. After harmonization of variables across cohorts, relative survival models were fitted in each cohort separately and results were combined using individual patient data meta-analysis among 466,892 individuals (1988-2019). When the donor was male, female recipients 0-12 years (Relative Excess Risk 1.54, 95% Confidence Interval 1.20-1.99), 13-24 years (1.17, 1.01-1.34), 25-44 years (1.11, 1.05-1.18) and 60 years and older (1.05, 1.02-1.08) showed higher excess mortality risks than male recipients of the same age. When the donor was female, the Relative Excess Risk for those over 12 years were similar to those when the donor was male. There is a higher excess mortality risk in female than male recipients with differences larger at younger than older ages and only statistically significant when the donor was male. While these findings may be partly explained by the known sex differences in graft loss risks, sex differences in the risks of death with graft function may also contribute. Thus, higher risks in females than males suggest that management needs to be modified to optimize transplant outcomes among females.

Differences in medication adherence by sex and organ type among adolescent and young adult solid organ transplant recipients

BACKGROUND

Identification of differences in medication adherence by sex or organ type may help in planning interventions to optimize outcomes. We compared immunosuppressive medication adherence between males and females, and between kidney, liver and heart transplant recipients.

METHODS

This multicenter study of prevalent kidney, liver and heart transplant recipients 14-25 years assessed adherence 3 times (0, 3, 6 months post-enrollment) with the BAASIS self-report tool. At each visit, participants were classified as adherent if they missed no doses in the prior 4 weeks and non-adherent otherwise. Adherence was also assessed using the coefficient of variation (CV) of tacrolimus trough levels; CV < 30% was classified as adherent. We used multivariable mixed effects logistic regression models adjusted for potential confounders to compare adherence by sex and by organ.

RESULTS

Across all visits, males (n = 150, median age 20.4 years, IQR 17.2-23.3) had lower odds of self-reported adherence than females (n = 120, median age 19.8 years, IQR 17.1-22.7) (OR 0.41, 95% CI 0.21-0.80) but higher odds of adherence by tacrolimus CV (OR 2.50, 95% CI 1.30-4.82). No significant differences in adherence (by self-report or tacrolimus CV) were noted between the 184 kidney, 58 liver, and 28 heart recipients.

CONCLUSION

Females show better self-reported adherence than males but greater variability in tacrolimus levels. Social desirability bias, more common in females than males, may contribute to better self-reported adherence among females. Higher tacrolimus variability among females may reflect biologic differences in tacrolimus metabolism between males and females rather than sex differences in adherence. There were no significant differences in adherence by organ type.

Disparities in Deceased Donor Kidney Offer Acceptance: A Survey of Canadian Transplant Nephrologists, General Surgeons and Urologists

Background

Significant variability in organ acceptance thresholds have been demonstrated across the United States, but data regarding the rate and rationale for kidney donor organ decline in Canada are lacking.

Objective

To examine decision making regarding deceased kidney donor acceptance and non-acceptance in a population of Canadian transplant professionals.

Design

A survey study of theoretical deceased donor kidney cases of increasing complexity.

Setting

Canadian transplant nephrologists, urologists, and surgeons making donor call decisions responding to an electronic survey between July 22 and October 4, 2022.

Participants

Invitations to participate were distributed to 179 Canadian transplant nephrologists, surgeons, and urologists through e-mail. Participants were identified by contacting each transplant program and requesting a list of physicians who take donor call.

Measurements

Survey respondents were asked whether they would accept or decline a given donor, assuming there was a suitable recipient. They were also asked to cite reasons for donor non-acceptance.

Methods

Donor scenario-specific acceptance rates (total acceptance divided by total number of respondents for a given scenario and overall) and reasons for decline were determined and presented as a percentage of the total cases declined.

Results

In all, 72 respondents from 7 provinces completed at least one question of the survey, with considerable variability between acceptance rates for centers; the most conservative center declined 60.9% of donor cases, whereas the most aggressive center declined only 28.1%, P-value < .001. There was an increased risk of non-acceptance with advancing age, donation after cardiac death, acute kidney injury, chronic kidney disease, and comorbidities.

Limitations

As with any survey, there is the potential for participation bias. In addition, this study examines donor characteristics in isolation, however, asks respondent to assume there is a suitable candidate available. In reality, whenever donor quality is considered, it should be considered in the context of the intended recipient.

Conclusion

In a survey of increasingly medically complex deceased kidney donor cases, there was significant variability in donor decline among Canadian transplant specialists. Given relatively high rates of donor decline and apparent heterogeneity in acceptance decisions, Canadian transplant specialists may benefit from additional education regarding the benefits achieved from even medically complex kidney donors for appropriate candidates relative to remaining on dialysis on the transplant waitlist.

Severity of COVID-19 among solid organ transplant recipients in Canada, 2020–2021: a prospective, multicentre cohort study

Background:

Severe COVID-19 appears to disproportionately affect people who are immunocompromised, although Canadian data in this context are limited. We sought to determine factors associated with severe COVID-19 outcomes among recipients of organ transplants across Canada.

Methods:

We performed a multicentre, prospective cohort study of all recipients of solid organ transplants from 9 transplant programs in Canada who received a diagnosis of COVID-19 from March 2020 to November 2021. Data were analyzed to determine risk factors for oxygen requirement and other metrics of disease severity. We compared outcomes by organ transplant type and examined changes in outcomes over time. We performed a multivariable analysis to determine variables associated with need for supplemental oxygen.

Results:

A total of 509 patients with solid organ transplants had confirmed COVID-19 during the study period. Risk factors associated with needing (n = 190), compared with not needing (n = 319), supplemental oxygen included age (median 62.6 yr, interquartile range [IQR] 52.5–69.5 yr v. median 55.5 yr, IQR 47.5–66.5; p < 0.001) and number of comorbidities (median 3, IQR 2–3 v. median 2, IQR 1–3; p < 0.001), as well as parameters associated with immunosuppression. Recipients of lung transplants (n = 48) were more likely to have severe disease with a high mortality rate (n = 15, 31.3%) compared with recipients of other organ transplants, including kidney (n = 48, 14.8%), heart (n = 1, 4.4%), liver (n = 9, 11.4%) and kidney–pancreas (n = 3, 12.0%) transplants (p = 0.02). Protective factors against needing supplemental oxygen included having had a liver transplant and receiving azathioprine. Having had 2 doses of SARS-CoV-2 vaccine did not have an appreciable influence on oxygen requirement. Multivariable analysis showed that older age (odds ratio [OR] 1.04, 95% confidence interval [CI] 1.02–1.07) and number of comorbidities (OR 1.63, 95% CI 1.30–2.04), among other factors, were associated with the need for supplemental oxygen. Over time, disease severity did not decline significantly.

Interpretation:

Despite therapeutic advances and vaccination of recipients of solid organ transplants, evidence of increased severity of COVID-19, in particular among those with lung transplants, supports ongoing public health measures to protect these at-risk people, and early use of COVID-19 therapies for recipients of solid organ transplants.

Outcomes of SARS-CoV-2 Infection in Unvaccinated Compared With Vaccinated Solid Organ Transplant Recipients: A Propensity Matched Cohort Study

BACKGROUND

Solid organ transplant (SOT) recipients are at high risk for complications from coronavirus disease 2019 (COVID-19). Vaccination may mitigate this risk; however, immunogenicity appears to be significantly impaired, with reports of increased risk of breakthrough infection. It is unknown if vaccine breakthrough infections are milder or as severe as infections in unvaccinated patients.

METHODS

We performed a multicenter matched cohort study between March 2020 and September 2021 to assess influence of COVID-19 vaccination on outcomes of COVID-19 infection. Treatment characteristics and disease severity outcomes were compared on the basis of vaccine status; breakthrough infections versus unvaccinated infections. Variable ratio propensity score matching based on age, sex, transplant type, and number of comorbidities, was used to develop the analytic cohort. Logistic regression was used to assess the influence of vaccination status on the selected outcomes.

RESULTS

From a cohort of 511 SOT patients with COVID-19, we matched 77 partially or fully vaccinated patients with 220 unvaccinated patients. Treatment characteristics including use of dexamethasone, remdesivir, and antibiotics did not differ. Vaccinated participants were more likely to receive tocilizumab, 15 of 77 (19.5%) versus 5 of 220 (2.3%), P  < 0.001. Disease severity outcomes including oxygen requirement, mechanical ventilation, and mortality were similar among medically attended vaccine breakthroughs compared with unvaccinated patients.

CONCLUSIONS

SOT recipients who develop medically attended COVID-19 following 1- or 2-dose vaccination seem to have similar disease severity to unvaccinated patients who develop infection. This is consistent with the requirement that SOT recipients need 3 or more vaccine doses and emphasizes the importance of alternate strategies for this population.

The promise of machine learning applications in solid organ transplantation

Solid-organ transplantation is a life-saving treatment for end-stage organ disease in highly selected patients. Alongside the tremendous progress in the last several decades, new challenges have emerged. The growing disparity between organ demand and supply requires optimal patient/donor selection and matching. Improvements in long-term graft and patient survival require data-driven diagnosis and management of post-transplant complications. The growing abundance of clinical, genetic, radiologic, and metabolic data in transplantation has led to increasing interest in applying machine-learning (ML) tools that can uncover hidden patterns in large datasets. ML algorithms have been applied in predictive modeling of waitlist mortality, donor–recipient matching, survival prediction, post-transplant complications diagnosis, and prediction, aiming to optimize immunosuppression and management. In this review, we provide insight into the various applications of ML in transplant medicine, why these were used to evaluate a specific clinical question, and the potential of ML to transform the care of transplant recipients. 36 articles were selected after a comprehensive search of the following databases: Ovid MEDLINE; Ovid MEDLINE Epub Ahead of Print and In-Process & Other Non-Indexed Citations; Ovid Embase; Cochrane Database of Systematic Reviews (Ovid); and Cochrane Central Register of Controlled Trials (Ovid). In summary, these studies showed that ML techniques hold great potential to improve the outcome of transplant recipients. Future work is required to improve the interpretability of these algorithms, ensure generalizability through larger-scale external validation, and establishment of infrastructure to permit clinical integration.

Age-dependent Sex Differences in Graft Loss After Kidney Transplantation

BACKGROUND

Sex differences in kidney graft loss rates were reported in the United States. Whether these differences are present in other countries is unknown.

METHODS

We estimated the association between recipient sex and death-censored graft loss in patients of all ages recorded in the Scientific Registry of Transplant Recipients, Australia and New Zealand Dialysis and Transplant Registry, and Collaborative Transplant Study registries who received a first deceased donor kidney transplant (1988-2019). We used multivariable Cox regression models, accounting for the modifying effects of donor sex and recipient age, in each registry separately; results were combined using individual patient data meta-analysis.

RESULTS

We analyzed 438 585 patients. Young female patients 13-24 y old had the highest crude graft loss rates (female donor: 5.66; male donor: 5.50 per 100 person-years). Among young recipients of male donors, females showed higher graft loss risks than males (0-12 y: adjusted hazard ratio [aHR] 1.42, (95% confidence interval [CI], 1.17-1.73); 13-24 y: 1.24 (1.17-1.32); 25-44 y: 1.09 (1.06-1.13)). When the donor was female, there were no significant differences by recipient sex among those of age <45 y; however, the aHR for females was 0.93 (0.89-0.98) in 45-59 y-old and 0.89 (0.86-0.93) in ≥ 60 y-old recipients. Findings were similar for all 3 registries in most age intervals; statistically significant heterogeneity was seen only among 13-24-y-old recipients of a female donor (I2 = 71.5%, P = 0.03).

CONCLUSIONS

There is an association between recipient sex and kidney transplantation survival that is modified by recipient age and donor sex.

Care processes and structures associated with higher medication adherence in adolescent and young adult transplant recipients

BACKGROUND

We aimed to identify care processes and structures that were independently associated with higher medication adherence among young transplant recipients.

METHODS

We conducted a prospective, observational cohort study of 270 prevalent kidney, liver, and heart transplant recipients 14-25 years old. Patients were ≥3 months post-transplant, ≥2 months post-discharge, and followed in one of 14 pediatric or 14 adult transplant programs in Canada. Patients were enrolled between June 2015 and March 2018 and followed for 6 months. Adherence was assessed at baseline, 3, and 6 months using the BAASIS^© self-report tool. Patients were classified as adherent if no doses were missed in the prior 4 weeks. Transplant program directors and nurses completed questionnaires regarding care organization and processes.

RESULTS

Of the 270 participants, 99 were followed in pediatric programs and 171 in adult programs. Median age was 20.3 years, and median time since transplant was 5 years. At baseline, 71.5% were adherent. Multivariable mixed effects logistic regression models with program as a random effect identified two program-level factors as independently associated with better adherence: minimum number of prescribed blood draws per year for those >3 years post-transplant (per 1 additional) (OR 1.12 [95% CI 1.00, 1.26]; p = .047), and average time nurses spend with patients in clinic (per 5 additional minutes) (OR 1.15 [1.03, 1.29]; p = .017).

CONCLUSION

Program-level factors including protocols with a greater frequency of routine blood testing and more nurse time with patients were associated with better medication adherence. This suggests that interventions at the program level may support better adherence.

Organ donor management and delayed graft function in kidney transplant recipients: A multicenter retrospective cohort study

Meeting donor management goals (DMGs) has been reported to decrease the incidence of delayed graft function (DGF) after kidney transplant, but whether this relationship is independent of cold machine perfusion is unclear. We aimed to determine whether meeting DMGs is associated with a reduced incidence of DGF, independent of the use of machine perfusion. We collected data on consecutive brain-dead donors and their KT recipients (KTRs) between June 2013 and December 2016 in 5 adult transplant centers. We evaluated whether DMGs were met at donor neurologic death (DND) and later time points. We defined a priori meeting optimal DMG as achieving ≥7 DMGs. Generalized estimating equations were used to predict DGF. Among 122 donors, 34% were extended-criteria donors (ECDs). The number of DMGs met increased over time (5.6 ± 1.4 at DND and 6.1 ± 1.3 at organ procurement [P < .001]). DGF occurred in 23% of 214 KTRs, and 55% received organs placed on machine perfusion. In multivariate analysis, ECD (odds ratio [OR] 2.24, 95% confidence interval [CI] 1.13-4.45), use of machine perfusion (OR 0.45, 95% CI 0.22-0.94), and optimal DMG at DND (OR 0.39, 95% CI 0.16-0.99) were associated with DGF. Early achievement of DMGs was associated with a reduced risk of the development of DGF, independent of the use of machine perfusion.

The determinants, biomarkers, and consequences of microvascular injury in kidney transplant recipients

Independent of the initial cause of kidney disease, microvascular injury to the peritubular capillary network appears to play a central role in the development of interstitial fibrosis in both native and transplanted kidney disease. This association is explained by mechanisms such as the upregulation of profibrotic genes and epigenetic changes induced by hypoxia, capillary leakage, endothelial and pericyte transition to interstitial fibroblasts, as well as modifications in the secretome of endothelial cells. Alloimmune injury due to antibody-mediated rejection and ischemia-reperfusion injury are the two main etiologies of microvascular damage in kidney transplant recipients. The presence of circulating donor-specific anti-human leukocyte antigen (HLA) antibodies, histological findings, such as diffuse C4d staining in peritubular capillaries, and the extent and severity of peritubular capillaritis, are commonly used clinically to provide both diagnostic and prognostic information. Complement-dependent assays, circulating non-HLA antibodies, or evaluation of the microvasculature with novel imaging techniques are the subject of ongoing studies.

The impact of repeated mismatches in kidney transplantations performed after nonrenal solid organ transplantation

The aim of this study was to determine whether kidney transplantations performed after previous nonrenal solid organ transplants are associated with worse graft survival when there are repeated HLA mismatches (RMM) with the previous donor(s). We performed a retrospective cohort study using data from the Scientific Registry of Transplant Recipients. Our cohort comprised 6624 kidney transplantations performed between January 1, 1990 and January 1, 2015. All patients had previously received 1 or more nonrenal solid organ transplants. RMM were observed in 35.3% of kidney transplantations and 3012 grafts were lost over a median follow-up of 5.4 years. In multivariate Cox regression analyses, we found no association between overall graft survival and either RMM in class 1 (hazard ratio [HR]: 0.97, 95% confidence interval [CI] 0.89-1.07) or class 2 (HR: 0.95, 95% CI 0.85-1.06). Results were similar for the associations between RMM, death-censored graft survival, and patient survival. Our results suggest that the presence of RMM with previous donor(s) does not have an important impact on allograft survival in kidney transplant recipients who have previously received a nonrenal solid organ transplant.

Epidemiology and outcome of antimicrobial resistance to gram-negative pathogens in bacteriuric kidney transplant recipients

BACKGROUND

In kidney transplant recipients, episodes of bacteriuria are often treated regardless of the presence of symptoms because of the lack of clear treatment guidelines suggesting otherwise. This practice may lead to the development of antimicrobial resistance. Our aim was to determine the incidence, determinants, and impact of antimicrobial resistance in kidney transplant recipients with gram-negative bacteriuria.

METHOD

We conducted a single-center, retrospective cohort study in patients who underwent kidney transplantation between January 2008 and June 2013. To identify risk factors for the development of resistance, we used a logistic regression model with generalized estimating equations to account for within-subject correlation.

RESULTS

Among the 318 patients who underwent kidney transplantation during the study period, 147 patients developed 555 gram-negative episodes of bacteriuria. Resistance to trimethoprim-sulfamethoxazole and quinolones, and production of extended-spectrum β-lactamase (ESBL) occurred in 52%, 21%, and 5% of isolated microorganisms, respectively. An increased risk of resistance to quinolones and production of ESBL were associated with concomitant diabetes (odds ratio [OR]: 2.29, 95% confidence interval [CI]: 1.11-4.74), the first year post transplantation (OR: 2.88, 95% CI: 1.36-6.09), and antibiotic treatment in the previous 6 months (OR: 3.36, 95% CI: 1.66-6.81). This resistance profile was also associated with the presence of symptoms, a longer duration of antibiotic treatment, and a higher rate of hospitalization.

CONCLUSION

Antimicrobial resistance to quinolones and production of ESBL were commonly seen, and were shown to demonstrate an adverse impact on outcomes in kidney transplant recipients with gram-negative bacteriuria. The decision on treatment for asymptomatic bacteriuria should be made with caution, given the potential for the selection of resistant strains.

Association of Sex with Risk of Kidney Graft Failure Differs by Age

Prior studies of sex differences in kidney graft survival showed conflicting results. We hypothesized that the association between recipient sex and kidney graft failure risk differs by recipient age and donor sex. We evaluated 159,417 patients recorded in the Scientific Registry of Transplant Recipients database who received a first deceased-donor kidney transplant (1995-2013). We used time-varying Cox models to estimate the association between recipient sex and death-censored graft failure. Models, stratified on donor sex and adjusted for potential confounders, included a recipient sex by current age interaction term. Among recipients of male donors, females of all ages had significantly higher graft failure risks than males (adjusted hazard ratios 0-14 years: 1.51 [95% confidence intervals 1.19 to 1.90]; 15-24 years: 1.37 [1.18 to 1.59]; 25-44 years: 1.14 [1.03 to 1.26]; 45 years: 1.05 [1.01 to 1.09]). Among recipients of female-donor grafts, only female recipients aged 15-24 years had a significantly higher graft failure risk than their male counterparts had (1.28 [1.06 to 1.53]). Indeed, female recipients aged ≥45 years had a significantly lower graft failure risk than their male counterparts had (0.95 [0.91 to 0.99]). These observations might be explained by the combined influence of several factors, including recognition of sex-determined minor histocompatibility antigens, influence of sex hormones on immune activation, sex- and age-related differences in medication adherence, and sex-related differences in body size. Additional studies should determine whether sex- and age-specific immunosuppression strategies are warranted for kidney graft recipients.

Anti-LG3 Antibodies Aggravate Renal Ischemia-Reperfusion Injury and Long-Term Renal Allograft Dysfunction

Pretransplant autoantibodies to LG3 and angiotensin II type 1 receptors (AT1R) are associated with acute rejection in kidney transplant recipients, whereas antivimentin autoantibodies participate in heart transplant rejection. Ischemia-reperfusion injury (IRI) can modify self-antigenic targets. We hypothesized that ischemia-reperfusion creates permissive conditions for autoantibodies to interact with their antigenic targets and leads to enhanced renal damage and dysfunction. In 172 kidney transplant recipients, we found that pretransplant anti-LG3 antibodies were associated with an increased risk of delayed graft function (DGF). Pretransplant anti-LG3 antibodies are inversely associated with graft function at 1 year after transplantation in patients who experienced DGF, independent of rejection. Pretransplant anti-AT1R and antivimentin were not associated with DGF or its functional outcome. In a model of renal IRI in mice, passive transfer of anti-LG3 IgG led to enhanced dysfunction and microvascular injury compared with passive transfer with control IgG. Passive transfer of anti-LG3 antibodies also favored intrarenal microvascular complement activation, microvascular rarefaction and fibrosis after IRI. Our results suggest that anti-LG3 antibodies are novel aggravating factors for renal IRI. These results provide novel insights into the pathways that modulate the severity of renal injury at the time of transplantation and their impact on long-term outcomes.

Human pregnancy and generation of anti-angiotensin receptor and anti-perlecan antibodies

Non-HLA antibodies against the angiotensin II type 1 receptor (AT1 R) and the C-terminal fragment of perlecan (i.e., LG3) are associated with the development of renal allograft rejection. It is currently unknown how humans develop anti-AT1 R or anti-LG3 antibodies. The aim of this study was to investigate whether pregnancy-as a model of sensitization to polymorphic proteins-induces anti-AT1 R and/or anti-LG3 antibodies. We included 104 samples from women obtained after physiologic full-term pregnancy and 80 samples from healthy nonsensitized controls (40 women and 40 men). Both anti-AT1 R and anti-LG3 antibody levels were lower in pregnancy samples than in controls (both P < 0.05). By multivariate analysis, male gender was an independent predictor for high anti-AT1 R antibody levels (OR 3.66, P = 0.04) and pregnancy was predictive for low anti-LG3 antibody levels (OR 6.53, P = 0.0001). There was no correlation of anti-AT1 R with anti-LG3 antibody levels, either in the pregnancy or in the control samples (r(2) ≤ 0.03, P ≥ 0.26). In conclusion, physiologic full-term pregnancy does not induce anti-AT1 R or anti-LG3 antibodies and may even lower their levels. Therefore, anti-AT1 R and anti-LG3 antibodies are likely not caused by allosensitization. The lack of correlation of anti-AT1 R with anti-LG3 antibodies suggests different mechanisms of generation, which remain to be elucidated.

Antiperlecan antibodies are novel accelerators of immune-mediated vascular injury

Acute vascular rejection (AVR) is characterized by immune-mediated vascular injury and heightened endothelial cell (EC) apoptosis. We reported previously that apoptotic ECs release a bioactive C-terminal fragment of perlecan referred to as LG3. Here, we tested the possibility that LG3 behaves as a neoantigen, fuelling the production of anti-LG3 antibodies of potential importance in regulating allograft vascular injury. We performed a case-control study in which we compared anti-LG3 IgG titers in kidney transplant recipients with AVR (n=15) versus those with acute tubulo-interstitial rejection (ATIR) (n=15) or stable graft function (n=30). Patients who experienced AVR had elevated anti-LG3 titers pre and posttransplantation compared to subjects with ATIR or stable graft function (p<0.05 for both mediators). Elevated pretransplant anti-LG3 titers (OR: 4.62, 95% CI: 1.08-19.72) and pretransplant donor-specific antibodies (DSA) (OR 4.79, 95% CI: 1.03-22.19) were both independently associated with AVR. To address the functional role of anti-LG3 antibodies in AVR, we turned to passive transfer of anti-LG3 antibodies in an animal model of vascular rejection based on orthotopic aortic transplantation between fully MHC-mismatched mice. Neointima formation, C4d deposition and allograft inflammation were significantly increased in recipients of an ischemic aortic allograft passively transferred with anti-LG3 antibodies. Collectively, these data identify anti-LG3 antibodies as novel accelerators of immune-mediated vascular injury and obliterative remodeling.

Endothelial dysfunction and oxidative stress in chronic renal failure

Uremic patients have an increased incidence of cardiovascular disease (CVD), endothelial dysfunction and oxidative stress that can contribute to cardiovascular (CV) events. To assess the relationship between endothelial dysfunction, oxidative stress and renal failure severity, we studied 40 patients (age 57 +/- 7 yrs, 24 males) affected by chronic kidney disease (CKD) K/DOQI stage 3-5 (serum creatinine (Cr) 5.6 +/- 2.2 mg/dL) on conservative treatment, 20 uremic patients (age 57 +/- 12 yrs, 13 males) on hemodialysis (HD) and 30 healthy controls (56 +/- 12 yrs, 20 males). Before and 2 hr after oral vitamin C (2 g) administration, we measured brachial artery endothelium-dependent vasodilation (flow mediated dilation (FMD)) to reactive hyperemia following 5 min of forearm ischemia and the response to sublingual glyceril trinitrate (GTN). Measurements were made by high-resolution ultrasound and computerized analysis. FMD was lower in CKD patients than in controls (5.3 +/- 2.2 vs. 6.9 +/- 2.8%; p<0.01) and was further reduced in HD patients (3.6 +/- 2.7; p<0.01 vs. CKD patients). Response to GTN was similar in all groups. FMD was related to Cr clearance (r=0.42; p<0.01) in CKD patients, while it related inversely to Kt/V(urea) (r=-0.52; p<0.05) in HD patients. After vitamin C administration, FMD was significantly enhanced in HD (4.7 +/- 2.4%; p<0.01 vs. baseline), but not in CKD patients. Response to GTN was unaffected. However, vitamin C load reduced oxidative stress markers, and increased plasma antioxidant capability in both groups. In conclusion, the reduced endothelium-dependent dilation in the brachial artery of CKD patients is related to renal failure severity. HD patients showed a more marked alteration, which seems to be related, at least in part, to increased oxidative stress.

Total cholesterol correlates with cyclosporine C2 levels in kidney transplant recipients under maintenance immunosuppression

The aim of this study was to assess the relationship between cyclosporine (CyA) trough level (C0) and 2-hour postdose (C2) and total cholesterol (TC) in kidney transplant (KT) recipients on Neoral maintenance immunosuppression. In KT recipients who had more than 5 years of follow-up, stable graft function, and stable Neoral dose, we measured C2 and C0 blood levels, serum creatinine, mean total cholesterol (TC) over the last 5 years, prednisone dose, use of beta-blockers and thiazides. Correlations between C0 and C2 levels and TC were performed with the Pearson coefficient. Receiver operating characteristics (ROCs) were used to define the threshold with greater accuracy for significant variables at the correlation test. Statistical tests were performed with SPSS 9.5 The C2 correlated with TC (0.31; P=.008) whereas C0 did not. The C2 level was an independent predictor for TC after adjusting for recipient age, gender, dose of prednisone, creatinine clearance, and use of beta-blockers and thiazides (B coefficient=1.124(E-3); P=.009). A threshold C2 value of 700 microg/L yielded to a TC level of 5.2 mmol/L. This is the first study to report a correlation between C2 levels and TC. Although C2 explained a small fraction of TC variability, it is an independent predictor of TC in KT recipients on Neoral maintenance immunosuppression. A long-term C2 value under 700 microg correlates with better control of hypercholesterolemia.

Mechanisms responsible for endothelial dysfunction induced by fasting hyperhomocystinemia in normotensive subjects and patients with essential hypertension

OBJECTIVES

We sought to evaluate whether fasting hyperhomocystinemia reduces endothelial function by oxidative stress in normotensive subjects and hypertensive patients.

BACKGROUND

Subjects with hyperhomocystinemia have endothelial dysfunction.

METHODS

In 23 normotensive subjects and 28 hypertensive patients, classified into normohomocystinemic and hyperhomocystinemic groups according to homocysteine plasma levels (< 8.7 and >14.6 micromol/l, respectively), we studied forearm blood flow changes (strain-gauge plethysmography) induced by intrabrachial administration of acetylcholine (0.15 to 15 microg/100 ml tissue per min) or sodium nitroprusside (1 to 4 microg/100 ml per min), an endothelium-dependent and -independent vasodilator, respectively. Acetylcholine was repeated with N(G)-monomethyl-L-arginine (L-NMMA; 100 microg/100 ml per min), vitamin C (8 mg/100 ml per min) and L-NMMA plus vitamin C.

RESULTS

Normotensive hyperhomocystinemic patients showed a blunted response to acetylcholine and a lower inhibiting effect of L-NMMA on acetylcholine, as compared with normohomocystinemic patients. Although vitamin C was ineffective in normohomocystinemic subjects, it increased the response to acetylcholine and restored the inhibiting effect of L-NMMA on acetylcholine in hyperhomocystinemic patients. Hypertensive hyperhomocystinemic patients showed a reduced response to acetylcholine, as compared with normohomocystinemic subjects. In both subgroups, L-NMMA failed to blunt the response to acetylcholine. The potentiating effect of vitamin C on acetylcholine was greater in hyperhomocystinemic patients than in normohomocystinemic subjects, although it restored the inhibitory effect of L-NMMA on acetylcholine-induced vasodilation to the same extent in both groups. Hyperhomocystinemia did not change the response to sodium nitroprusside.

CONCLUSIONS

In normotensive subjects and hypertensive patients, hyperhomocystinemia impairs endothelium-dependent vasodilation. It could be related to oxidant activity.

Influence of glomerular filtration rate on non-(1-84) parathyroid hormone (PTH) detected by intact PTH assays

BACKGROUND

Commercial intact parathyroid hormone (I-PTH) assays detect molecular form(s) of human PTH, non-(1-84) PTH, different from the 84-amino acid native molecule. These molecular form(s) accumulate in hemodialyzed patients. We investigated the importance of non-(1-84) PTH in the interpretation of the increased I-PTH in progressive renal failure.

METHODS

Five groups were studied: 26 healthy individuals, 12 hemodialyzed patients, and 31 patients with progressive renal failure subdivided according to their glomerular filtration rate (GFR) into 11 with a GFR between 60 and 100 mL. min(-1). 1.73 m(-2), 12 with a GFR between 30 and 60 mL. min(-1). 1.73 m(-2), and 8 with a GFR between 5 and 30 mL. min(-1). 1.73 m(-2). We evaluated indicators of calcium and phosphorus metabolism and creatinine clearance (CrCl) in the progressive renal failure groups, and the HPLC profile of I-PTH and C-terminal PTH in all groups.

RESULTS

Only patients with a GFR <30 mL. min(-1). 1.73 m(-2) and hemodialyzed patients had decreased Ca(2+) and 1,25-dihydroxyvitamin D, and increased phosphate. In patients with progressive renal failure, I-PTH was related to Ca(2+) (r = -0.66; P <0.0001), CrCl (r = -0.61; P <0.001), 1,25-dihydroxyvitamin D (r = -0.40; P <0.05), and 25-hydroxyvitamin D (r = -0.49; P <0.01) by simple linear regression. The importance of non-(1-84) PTH in the composition of I-PTH increased with each GFR decrease, being 21% in healthy individuals, 32% in progressive renal failure patients with a GFR <30 mL. min(-1). 1.73 m(-2), and 50% in hemodialyzed patients, with PTH(1-84) making up the difference.

CONCLUSIONS

As I-PTH increases progressively with GFR decrease, part of the increase is associated with the accumulation of non-(1-84) PTH, particularly when the GFR is <30 mL. min(-1). 1.73 m(-2). Concentrations of I-PTH 1.6-fold higher than in healthy individuals are necessary in hemodialyzed patients to achieve PTH(1-84) concentrations similar to those in the absence of renal failure.

The set point of parathyroid hormone stimulation by calcium is normal in progressive renal failure

An increased set point of PTH stimulation by ionized calcium (Ca++) has been observed in renal failure patients with severe secondary hyperparathyroidism. The extension of this concept to all renal failure patients has remained problematic, even if it could explain elevated PTH levels in the absence of other biochemical abnormalities. We were particularly interested in seeing whether the concept could fit patients with progressive renal failure (PRF). To achieve this, we studied 26 normals (N), 9 patients with PRF, and 12 hemodialyzed patients (HD) in the basal state and during parathyroid function tests. The latter two groups were studied at the end of winter and end of summer, respectively. Patients with PRF had normal levels of Ca++, PO4, and 1,25(OH)2D, and they had low-normal concentrations of 25(OH)D; their basal I- and C-PTH levels were 3- and 4-fold higher than N, as were their creatinine levels. HD had significantly lower levels of Ca++ and 1,25(OH)2D, and they had higher levels of phosphate, creatinine, I-PTH, and C-PTH than N or PRF. Stimulated levels of I-PTH were similar in N (13.6 +/- 4.3 pmol/L) and PFR (18 +/- 3.3 pmol/L) and elevated in HD (37.1 +/- 28.7 pmol/L; P < 0.001 vs. N, and P < 0.05 vs. PRF). Nonsuppressible I-PTH was increased 2-fold in PRF (N = 0.64 +/- 0.19 vs. PRF = 1.28 +/- 0.46 pmol/L; P < 0.01) and 6-fold in HD (3.95 +/- 2.85 pmol/L; P < 0.001 vs. others). But the set point of I-PTH stimulation by Ca++ was normal in PRF (N = 1.18 +/- 0.03 vs. PRF = 1.20 +/- 0.04 mmol/L; not significant) and decreased in HD (1.09 +/- 0.04 mmol/L; P < 0.001 vs. others). Similar results were obtained with the set point of C-PTH and of the C-PTH/I-PTH ratio. A positive correlation was observed between serum Ca++ concentration and the set point value when all three populations were analyzed together (r = 0.759, n = 47, P < 0.0001). These results indicate that the set point of PTH stimulation is normal in PRF and decreased in hypocalcemic HD. The set point seems to adjust to the ambient Ca++ concentration of the patients, by mechanisms yet to be elucidated. This does not suggest participation of this factor to the genesis of the secondary hyperparathyroidism of PRF.