Clinical Genetic Testing for APOL1: Are we There Yet?

APOL1 polymorphisms are not influencing acute coronary syndrome risk in Czech males

BACKGROUND

The highest mortality and morbidity worldwide is associated with atherosclerotic cardiovascular disease (ASCVD), which has in background both environmental and genetic risk factors. Apolipoprotein L1 (APOL1) variability influences the risk of ASCVD in Africans, but little is known about the APOL1 and ASCVD in other ethnic groups.

METHODS

To investigate the role of APOL1 and ASCVD, we have genotyped four (rs13056427, rs136147, rs10854688 and rs9610473) APOL1 polymorphisms in a group of 1541 male patients with acute coronary syndrome (ACS) and 1338 male controls.

RESULTS

Individual APOL1 polymorphisms were not associated with traditional CVD risk factors such as smoking, hypertension or diabetes prevalence, with BMI values or plasma lipid levels. Neither individual polymorphisms nor haplotypes were associated with an increased risk of ACS nor did they predict total or cardiovascular mortality over the 10.2 ± 3.9 years of follow-up.

CONCLUSIONS

We conclude that APOL1 genetic variability has no major effect on risk of ACS in Caucasians.

Phenome-wide analysis reveals epistatic associations between APOL1 variants and chronic kidney disease and multiple other disorders

BACKGROUND

APOL1 variants G1 and G2 are common in populations with recent African ancestry. They are associated with protection from African sleeping sickness, however homozygosity or compound heterozygosity for these variants is associated with chronic kidney disease (CKD) and related conditions. What is not clear is the extent of associations with non-kidney-related disorders, and whether there are clusters of diseases associated with individual APOL1 genotypes.

METHODS

Using a cohort of 7462 UK Biobank participants with recent African ancestry, we conducted a phenome-wide association study investigating associations between individual APOL1 genotypes and conditions identified by the International Classification of Disease phenotypes.

FINDINGS

We identified 27 potential associations between individual APOL1 genotypes and a diverse range of conditions. G1/G2 compound heterozygotes were specifically associated with 26 of these conditions (all deleteriously), with an over-representation of infectious diseases (including hospitalisation and death resulting from COVID-19). The analysis also exposed complexities in the relationship between APOL1 and CKD that are not evident when risk variants are grouped together: G1 homozygosity, G2 homozygosity, and G1/G2 compound heterozygosity were each shown to be associated with distinct CKD phenotypes. The multi-locus nature of the G1/G2 genotype means that its associations would go undetected in a standard genome-wide association study.

INTERPRETATION

Our findings have implications for understanding health risks and better-targeted detection, intervention, and therapeutic strategies, particularly in populations where APOL1 G1 and G2 are common such as in sub-Saharan Africa and its diaspora.

FUNDING

This study was funded by the Wellcome Trust (209511/Z/17/Z) and H3Africa (H3A/18/004).

Precision medicine implementation challenges for APOL1 testing in chronic kidney disease in admixed populations

Chronic Kidney Disease (CKD) is a public health problem that presents genetic and environmental risk factors. Two alleles in the Apolipoprotein L1 (APOL1) gene were associated with chronic kidney disease; these alleles are common in individuals of African ancestry but rare in European descendants. Genomic studies on Afro-Americans have indicated a higher prevalence and severity of chronic kidney disease in people of African ancestry when compared to other ethnic groups. However, estimates in low- and middle-income countries are still limited. Precision medicine approaches could improve clinical outcomes in carriers of risk alleles in the Apolipoprotein L1 gene through early diagnosis and specific therapies. Nevertheless, to enhance the definition of studies on these variants, it would be necessary to include individuals with different ancestry profiles in the sample, such as Latinos, African Americans, and Indigenous peoples. There is evidence that measuring genetic ancestry improves clinical care for admixed people. For chronic kidney disease, this knowledge could help establish public health strategies for monitoring patients and understanding the impact of the Apolipoprotein L1 genetic variants in admixed populations. Therefore, researchers need to develop resources, methodologies, and incentives for vulnerable and disadvantaged communities, to develop and implement precision medicine strategies and contribute to consolidating diversity in science and precision medicine in clinical practice.

The evolving role of diagnostic genomics in kidney transplantation

Monogenic forms of heritable kidney disease account for a significant proportion of chronic kidney disease (CKD) across both pediatric and adult patient populations and up to 11% of patients under 40 years reaching end-stage kidney failure (KF) and awaiting kidney transplant. Diagnostic genomics in the field of nephrology is ever evolving and now plays an important role in assessment and management of kidney transplant recipients and their related donor pairs. Genomic testing can help identify the cause of KF in kidney transplant recipients and assist in prognostication around graft survival and rate of recurrence of primary kidney disease. If a gene variant has been identified in the recipient, at-risk related donors can be assessed for the same and excluded if affected. This paper aims to address the indications for genomic testing in the context for kidney transplantation, the technologies available for testing, the conditions and groups in which testing should be most often considered, and the role for the renal genetics multidisciplinary team in this process.

Apolipoprotein L1 Opinions of African American Living Kidney Donors, Kidney Transplant Patients, and Nonpatients

INTRODUCTION

The discovery of apolipoprotein L1 (ApoL1) has raised important ethical and clinical questions about genetic testing in the context of living and deceased kidney donation. Largely missing from this discussion are the perspectives of those African Americans (AA) most likely to be impacted by ApoL1 testing.

METHODS

We surveyed 331 AA potential and former living kidney donors (LKDs), kidney transplant candidates and recipients, and nonpatients at three United States transplant programs about their ApoL1 testing attitudes.

RESULTS

Overall, 72% felt that transplant programs should offer ApoL1 testing to AA potential LKDs. If a potential LKD has the high-risk genotype, 79% felt that the LKD should be allowed to make their own donation decision or participate in shared decision-making with transplant doctors. More than half of the potential LKDs (58%) would undergo ApoL1 testing and 81% of former LKDs would take the test now if offered. Most transplant candidates expressed a low likelihood of accepting a kidney from a LKD (79%) or a deceased donor (67%) with the high-risk genotype.

CONCLUSIONS

There is strong support among LKDs and transplant patients for ApoL1 testing when evaluating potential kidney donors of African ancestry. Inclusion of AA stakeholders in developing guidelines and educational programs for ApoL1 testing is critical.

Apolipoprotein L1 variability is associated with increased risk of renal failure in the Czech population

BACKGROUND

With stage 5 chronic kidney disease (CKD5) more prevalent in the Czech Republic than in most European countries, genetic susceptibility is potentially implicated.

METHODS

In a group of 1489 CKD5 kidney transplantation patients (93% with complete clinical characteristics; mean age 52.0 years, 37% females) and 2559 healthy controls (mean age 49.0 years, 51% females), we examined the prevalence of six APOL1 SNPs (rs73885319, rs71785313, rs13056427, rs136147, rs10854688 and rs9610473) and one newly detected 55-nucleotide insertion/deletion polymorphism.

RESULTS

The rs73885319 and rs71785313 variants were monomorphic in the Czech Caucasian population. Genotype frequencies of the three SNPs examined (rs13056427, rs136147 and rs9610473) were almost identical in patients and controls (all P values were between 0.39 and 0.91). Minor homozygotes of rs10854688 were more common between the patients (13.2%) than in controls (10.7%) (OR [95% CI]; 1.32 [1.08-1.64]; P < 0.01). Prevalence of the newly detected 55-bp APOL1 deletion was significantly higher in CKD5 patients (3.0% vs. 1.7%; OR [95% CI]; 1.80 [1.16-2.80]; P < 0.01) compared to controls. Frequencies of some individual APOL1 haplotypes were borderline different between patients and controls.

CONCLUSION

We found an association between rs10854688 SNP within the APOL1 gene and end-stage renal disease in the Czech Caucasian population. Further independent studies are required before a conclusive association between the newly detected APOL1 insertion/deletion polymorphism and CKD5 can be confirmed.

Type I interferon-related kidney disorders

Type I interferon (IFN-I) mediates tissue damage in a wide range of kidney disorders, directly affecting the biology and function of several renal cell types including podocytes, mesangial, endothelial and parietal epithelial cells (PECs).Enhanced IFN-I signalling is observed in the context of viral infections, autoimmunity (e.g., systemic lupus erythematosus, SLE), and the type 1 interferonopathies (T1Is), rare monogenic disorders characterised by constitutive activation of the IFN-I pathway. All of these IFN I-related disorders can cause renal dysfunction, and share pathogenic and histopathological features. Collapsing glomerulopathy, a histopathological lesion characterised by podocyte loss, collapse of the vascular tuft and PEC proliferation, is commonly associated with viral infections, has been described in T1Is such as Aicardi-Goutières syndrome and STING-associated vasculopathy with onset in infancy (SAVI), and can also be induced by recombinant IFN-therapy. In all of these conditions, podocytes and PECs seem to be the primary target of IFN I-mediated damage. Additionally, immune-mediated glomerular injury is common to viral infections, SLE, and T1Is such as COPA syndrome and DNASE1L3 deficiency, diseases in which IFN-I apparently promotes immune-mediated kidney injury. Finally, kidney pathology primarily characterised by vascular lesions (e.g., thrombotic microangiopathy, vasculitis) is a hallmark of the T1I ADA2 deficiency as well as of SLE, viral infections and IFN-therapy.Defining the nosology, pathogenic mechanisms and histopathological patterns of IFN I-related kidney disorders has diagnostic and therapeutic implications, especially considering the likely near-term availability of novel drugs targeting the IFN-I pathway.

Impact of education on APOL1 testing attitudes among prospective living kidney donors

It is unknown how providing prospective living donors with information about APOL1, including the benefits and drawbacks of testing, influences their desire for testing. In this study, we surveyed 102 participants with self-reported African ancestry and positive family history of kidney disease, recruited from our nephrology waiting room. We assessed views on APOL1 testing before and after presentation of a set of potential benefits and drawbacks of testing and quantified the self-reported level of influence individual benefits and drawbacks had on participants' desire for testing in the proposed context of living donation. The majority of participants (92%) were aware of organ donation and more than half (56%) had considered living donation. And though we found no significant change in response following presentation of the potential benefits and the drawbacks of APOL1 testing by study end significance, across all participants, "becoming aware of the potential risk of kidney disease among your immediate family" was the benefit with the highest mean influence (3.3±1.4), while the drawback with the highest mean influence (2.9±1.5) was "some transplant centers may not allow you to donate to a loved one". This study provides insights into the priorities of prospective living donors and suggests concern for how the information affects family members may strongly influence desires for testing. It also highlights the need for greater community engagement to gain a deeper understanding of the priorities that influence decision making on APOL1 testing.

Diagnosis, Education, and Care of Patients with APOL1-Associated Nephropathy: A Delphi Consensus and Systematic Review

BACKGROUND

APOL1 variants contribute to the markedly higher incidence of ESKD in Blacks compared with Whites. Genetic testing for these variants in patients with African ancestry who have nephropathy is uncommon, and no specific treatment or management protocol for APOL1-associated nephropathy currently exists.

METHODS

A multidisciplinary, racially diverse group of 14 experts and patient advocates participated in a Delphi consensus process to establish practical guidance for clinicians caring for patients who may have APOL1-associated nephropathy. Consensus group members took part in three anonymous voting rounds to develop consensus statements relating to the following: (1) counseling, genotyping, and diagnosis; (2) disease awareness and education; and (3) a vision for management of APOL1-associated nephropathy in a future when treatment is available. A systematic literature search of the MEDLINE and Embase databases was conducted to identify relevant evidence published from January 1, 2009 to July 14, 2020.

RESULTS

The consensus group agreed on 55 consensus statements covering such topics as demographic and clinical factors that suggest a patient has APOL1-associated nephropathy, as well as key considerations for counseling, testing, and diagnosis in current clinical practice. They achieved consensus on the need to increase awareness among key stakeholders of racial health disparities in kidney disease and of APOL1-associated nephropathy and on features of a successful education program to raise awareness among the patient community. The group also highlighted the unmet need for a specific treatment and agreed on best practice for management of these patients should a treatment become available.

CONCLUSIONS

A multidisciplinary group of experts and patient advocates defined consensus-based guidance on the care of patients who may have APOL1-associated nephropathy.

Association Between APOL1 Genotype and Kidney Diseases and Annual Kidney Function Change: A Systematic Review and Meta-Analysis of the Prospective Studies

Background

Two coding risk variants in the Apo L1 gene (APOL1) underlie most of the excess risk for kidney diseases in recent African ancestry patients. Strength and consistency of the relationship between APOL1 high-risk genotypes and the risk of chronic kidney diseases (CKD) and end-stage renal disease (ESRD) are not uniform.

Objective

To conduct a systematic review and meta-analysis of prospective studies assessing the association of APOL1 genotypes and the risk of developing CKD, ESRD, and CKD to ESRD in adults.

Methods

Systematic search of MEDLINE, EMBASE, and Google Scholar was performed for prospective studies assessing the associations between APOL1 genotypes and CKD, ESRD, and progression from CKD to ESRD. Secondary analyses were to evaluate the annual kidney function change by APOL1 gene status. Random effects models were used to estimate pooled risk ratios (RRs) and weighted mean differences for outcomes of interest.

Results

The search yield 10 prospective during a follow-up period ranging from 4.4 to 25 years. The high-risk APOL1 genotype was associated with the incidence of CKD (RR:1.41[95% CI: 1.14–1.75]), the progression from CKD to ESRD (RR: 1.70[95% CI:1.44; 2.01]) compared with the low-risk APOL1 genotype. There was no appreciable association between high-risk APOL1 genotype with the incidence of ESRD. Furthermore, high-risk APOL1 genotype was associated with a marginal decrement in the annual eGFR decline (−0.55[95% CI: −0.94 to −0.16]) mL/min/1.73m² compared with low-risk APOL1 genotype status.

Conclusion

In summary, African Americans carrying APOL1 high-risk genotypes are at increased risk of developing CKD and ESRD. Given that the APOL1 risk alleles are common among individuals with African ancestry, with ~18% of African Americans carrying high-risk alleles, these findings highlight the potential identification of subgroups of patients who may benefit from APOL1 screening and developing culturally-appropriate interventions.

Opinions of African American adults about the use of apolipoprotein L1 (ApoL1) genetic testing in living kidney donation and transplantation

Apolipoprotein L1 (ApoL1) predictive genetic testing for kidney disease, and its emerging role in transplantation, remains controversial as it may exacerbate underlying disparities among African Americans (AAs) at increased risk. We conducted an online simulation among AAs (N = 585) about interest in ApoL1 testing and its cofactors, under 2 scenarios: as a potential living donor (PLD), and as a patient awaiting transplantation. Most respondents (61%) expressed high interest in genetic testing as a PLD: age ≥35 years (adjusted odds ratio [aOR], 1.75; 95% confidence interval [CI], 1.18, 2.60, P = .01), AA identity (aOR, 1.67; 95% CI, 1.02, 2.72, P = .04), perceived kidney disease risk following donation (aOR, 1.68; 95% CI, 1.03, 2.73, P = .03), interest in genetics (aOR, 2.89; 95% CI, 1.95, 4.29, P = .001), and genetics self-efficacy (aOR, 2.38; 95% CI, 1.54, 3.67, P = .001) were positively associated with ApoL1 test interest. If awaiting transplantation, most (89%) believed that ApoL1 testing should be done on AA deceased donors, and older age (aOR, 1.85; 95% CI, 1.03, 3.32, P = .04) and greater interest in genetics (aOR, 2.61; 95% CI, 1.41, 4.81, P = .002) were associated with interest in testing deceased donors. Findings highlight strong support for ApoL1 testing in AAs and the need to examine such opinions among PLDs and transplant patients to enhance patient education efforts.

Racism and Kidney Health: Turning Equity Into a Reality

Kidney disease continues to manifest stark racial inequities in the United States, revealing the entrenchment of racism and bias within multiple facets of society, including in our institutions, practices, norms, and beliefs. In this perspective, we synthesize theory and evidence to describe why an understanding of race and racism is integral to kidney care, providing examples of how kidney health disparities manifest interpersonal and structural racism. We then describe racialized medicine and "colorblind" approaches as well as their pitfalls, offering in their place suggestions to embed antiracism and an "equity lens" into our practice. We propose examples of how we can enhance kidney health equity by enhancing our structural competency, using equity-focused race consciousness, and centering investigation and solutions around the needs of the most marginalized. To achieve equitable outcomes for all, our medical institutions must embed antiracism and equity into all aspects of advocacy, policy, patient/community engagement, educational efforts, and clinical care processes. Organizations engaged in kidney care should commit to promoting structural equity and eliminating potential sources of bias across referral practices, guidelines, research agendas, and clinical care. Kidney care providers should reaffirm our commitment to structurally competent patient care and educational endeavors in which empathy and continuous self-education about social drivers of health and inequity, racism, and bias are integral. We envision a future in which kidney health equity is a reality for all. Through bold collective and sustained investment, we can achieve this critical goal.

APOL1 risk variants and the development of HIV-associated nephropathy

HIV-associated nephropathy (HIVAN) remains a concern among untreated HIV patients, notably of African descent, as patients can reach end-stage renal disease within 3 years. Two variants (G1 and G2) of the APOL1 gene, common in African populations to protect against African sleeping sickness, have been associated with an increased risk of several glomerular disorders including HIVAN, hypertension-attributed chronic kidney disease, and idiopathic focal segmental glomerulosclerosis and are accordingly named renal risk variants (RRVs). This review examines the mechanisms by which APOL1 RRVs drive glomerular injury in the setting of HIV infection and their potential application to patient management. Innate antiviral mechanisms activated by chronic HIV infection, especially those involving type 1 interferons, are of particular interest as they have been shown to upregulate APOL1 expression. Additionally, the downregulation of miRNA 193a (a repressor of APOL1) is also associated with the upregulation of APOL1. Interestingly, glomerular damage affected by APOL1 RRVs is caused by both loss- and gain-of-function changes in the protein, explicitly characterizing these effects. Their intracellular localization offers a further understanding of the nuances of APOL1 variant effects in promoting renal disease. Finally, although APOL1 variants have been recognized as a critical genetic player in mediating kidney disease, there are significant gaps in their application to patient management for screening, diagnosis, and treatment.

Inherited glomerular diseases in the gilded age of genomic advancements

The synchronized advent of high-throughput next-generation sequencing technology and knowledge of the human genome has rendered exponential contributions to our understanding of the pathophysiology of glomerular kidney diseases. A genetic diagnosis can now be made or confirmed in about two-thirds of the suspected inherited glomerular diseases. Next-generation sequencing is adept at identifying single nucleotide variations and small insertions or deletions that constitute majority of the disease-causing mutations. Description of the complete mutation spectrum in syndromic glomerulopathies may require the use of both sequencing and cytogenetic methods to detect large structural DNA variation in addition to single nucleotide changes. The enthusiastic application of genetic and genomic knowledge to inherited glomerular diseases has uncovered anticipated and unforeseen challenges mainly related to the biological interpretation of variants of uncertain significance and the limited benefit on clinical management for the individual patient when a diagnosis is obtained. To attain the ultimate goal of transforming clinical decision-making based on accurate genetic diagnosis using genomic information, these challenges need to be addressed. Till then, the glory of genomic medicine stands the test of time in this gilded age of genomic advancements.

Frequency of ClinVar Pathogenic Variants in Chronic Kidney Disease Patients Surveyed for Return of Research Results at a Cleveland Public Hospital

Return of results is not common in research settings as standards are not yet in place for what to return, how to return, and to whom. As a pioneer of large-scale of return of research results, the Precision Medicine Initiative Cohort now known of All of Us plans to return pharmacogenomic results and variants of clinical significance to its participants starting late 2019. To better understand the local landscape of possibilities regarding return of research results, we assessed the frequency of pathogenic variants and APOL1 renal risk variants in a small diverse cohort of chronic kidney disease patients (CKD) ascertained from a public hospital in Cleveland, Ohio genotyped on the Illumina Infinium MegaEX. Of the 23,720 ClinVar-designated variants directly assayed by the MegaEX, 8,355 (35%) had at least one alternate allele in the 130 participants genotyped. Of these, 18 ClinVar variants deemed pathogenic by multiple submitters with no conflicts in interpretation were distributed across 27 participants. The majority of these pathogenic ClinVar variants (14/18) were associated with autosomal recessive disorders. Of note were four African American carriers of TTR rs76992529 associated with amyloidogenic transthyretin amyloidosis, otherwise known as familial transthyretin amyloidosis (FTA). FTA, an autosomal dominant disorder with variable penetrance, is more common among African-descent populations compared with European-descent populations. Also common in this CKD population were APOL1 renal risk alleles G1 (rs73885319) and G2 (rs71785313) with 60% of the study population carrying at least one renal risk allele. Both pathogenic ClinVar variants and APOL1 renal risk alleles were distributed among participants who wanted actionable genetic results returned, wanted genetic results returned regardless of actionability, and wanted no results returned. Results from this local genetic study highlight challenges in which variants to report, how to interpret them, and the participant's potential for follow-up, only some of the challenges in return of research results likely facing larger studies such as All of Us.

Practical Considerations for APOL1 Genotyping in the Living Kidney Donor Evaluation

BACKGROUND

Association between the apolipoprotein L1 gene (APOL1) and nephropathy has altered the epidemiology of chronic kidney disease. In addition, donor APOL1 genotypes play important roles in the time to allograft failure in kidneys transplanted from deceased donors and the safety of living kidney donation.

METHODS

This article reviews genetic testing for inherited kidney disease in living kidney donors to improve donor safety. APOL1 genotyping in donors with recent African ancestry is considered.

RESULTS

Based on current data, transplant physicians should discuss APOL1 genotyping with potential living kidney donors self-reporting recent African ancestry. Until results from APOL1 Long-term Kidney Transplant Outcomes Network ancillary studies are available, we present practical approaches from our experience for considering APOL1 genotyping in the living donor evaluation.

CONCLUSIONS

Transplant physicians should inform potential living kidney donors at risk for APOL1-associated nephropathy about the gene and possibility of genetic testing early in the donor evaluation, well before scheduling the donor nephrectomy. Transplant programs must weigh risks of performing a donor nephrectomy in those with 2 APOL1 renal risk variants (high-risk genotypes), particularly younger individuals. Our program counsels kidney donors with APOL1 high-risk genotypes in the same fashion as with risk genotypes in other nephropathy genes. Because most African American kidney donor candidates lacking hypertension, proteinuria and reduced kidney function after workup will not possess APOL1 high-risk genotypes, genetic testing is unlikely to markedly increase donor declines and may reassure donors with regard to their long-term kidney outcomes, potentially increasing the number of African American donors.

Cases in Precision Medicine: APOL1 and Genetic Testing in the Evaluation of Chronic Kidney Disease and Potential Transplant

This article discusses potential indications for genetic testing in an African American patient with chronic kidney disease who is being evaluated for a kidney transplant. Two known risk variants in the APOL1 (apolipoprotein L1) gene predispose to kidney disease and are found almost exclusively in persons of African ancestry. APOL1 risk variants are considered, including whether clinicians should incorporate genetic testing in the screening process for living kidney donors. In addition to APOL1 testing, the role of diagnostic exome sequencing in evaluating potential transplant recipients and donors with a positive family history of kidney disease is discussed.

APOL1 Genetic Testing in Living Kidney Transplant Donors

The presence of 2 apolipoprotein L1 gene (APOL1) risk variants is associated with increased risk for chronic kidney disease and end-stage kidney disease. Inferior allograft outcomes following transplantation with kidneys from donors with 2 risk variants have also been reported. These data, coupled with anecdotal case reports and a recent cohort study of living donors, raise important questions about the potential increased kidney disease risk for living donors with APOL1 risk variants and the need for testing as part of the standard living donor evaluation process. We identify a series of questions that are central to the development of clinical policy regarding APOL1 testing of potential living kidney donors given the current uncertainty over the clinical implications of having 2 risk variants. We explore the ethical challenges that arise when determining when and to whom APOL1 testing should be offered, what potential donors should be told about APOL1 testing, how test results should be used to determine suitability for donation, if and when recipients should have access to results, and how clinical policy regarding APOL1 testing should be established.

Racial disparities in end-stage renal disease in a high-risk population: the Southern Community Cohort Study

INTRODUCTION

The Southern Community Cohort Study is a prospective study of low socioeconomic status (SES) blacks and whites from the southeastern US, where the burden of end-stage renal disease (ESRD) and its risk factors are high. We tested whether the 2.4-fold elevated risk of ESRD we previously observed in blacks compared to whites was explained by differences in baseline kidney function.

METHODS

We conducted a case-cohort study of incident ESRD cases (n = 737) with stored blood and a probability sampled subcohort (n = 4238) and calculated estimated glomerular filtration rate (eGFR) from serum creatinine. 86% of participants were enrolled from community health centers in medically underserved areas and 14% from the general population in 12 states in the southeastern United States. Incident ESRD after entry into the cohort was ascertained by linkage of the cohort with the US Renal Data System (USRDS).

RESULTS

Median (25th, 75th percentile) eGFR at baseline was 63.3 (36.0, 98.2) ml/min/1.73m2 for ESRD cases and 103.2 (86.0, 117.9) for subcohort. Black ESRD cases had higher median (25th, 75th) eGFR [63.3 (35.9, 95.9)] compared to whites [59.1 (39.4, 99.2)]. In multivariable Cox models accounting for sampling weights, baseline eGFR was a strong predictor of ESRD risk, and an interaction with race was detected (P = 0.029). The higher ESRD risk among blacks relative to whites persisted (hazard ratio: 2.58; 95% confidence interval: 1.65, 4.03) after adjustment for eGFR.

CONCLUSION

In this predominantly lower SES cohort, the racial disparity in ESRD risk is not explained by differences in baseline kidney function.

Hyperfiltration-mediated Injury in the Remaining Kidney of a Transplant Donor

Kidney donors face a small but definite risk of end-stage renal disease 15 to 30 years postdonation. The development of proteinuria, hypertension with gradual decrease in kidney function in the donor after surgical resection of 1 kidney, has been attributed to hyperfiltration. Genetic variations, physiological adaptations, and comorbidities exacerbate the hyperfiltration-induced loss of kidney function in the years after donation. A focus on glomerular hemodynamics and capillary pressure has led to the development of drugs that target the renin-angiotensin-aldosterone system (RAAS), but these agents yield mixed results in transplant recipients and donors. Recent work on glomerular biomechanical forces highlights the differential effects of tensile stress and fluid flow shear stress (FFSS) from hyperfiltration. Capillary wall stretch due to glomerular capillary pressure increases tensile stress on podocyte foot processes that cover the capillary. In parallel, increased flow of the ultrafiltrate due to single-nephron glomerular filtration rate elevates FFSS on the podocyte cell body. Although tensile stress invokes the RAAS, FFSS predominantly activates the cyclooxygenase 2-prostaglandin E2-EP2 receptor axis. Distinguishing these 2 mechanisms is critical, as current therapeutic approaches focus on the RAAS system. A better understanding of the biomechanical forces can lead to novel therapeutic agents to target FFSS through the cyclooxygenase 2-prostaglandin E2-EP2 receptor axis in hyperfiltration-mediated injury. We present an overview of several aspects of the risk to transplant donors and discuss the relevance of FFSS in podocyte injury, loss of glomerular barrier function leading to albuminuria and gradual loss of renal function, and potential therapeutic strategies to mitigate hyperfiltration-mediated injury to the remaining kidney.

Biomarkers in Solid Organ Transplantation

After more than 6 decades of clinical practice, the transplant community continues to research noninvasive biomarkers of solid organ injury to help improve patient care. In this review, we discuss the clinical usefulness of selective biomarkers and how they are processed at the laboratory. In addition, we organize these biomarkers based on specific aims and introduce innovative markers currently under investigation.

Apolipoprotein L1 nephropathies: 2017 in review

PURPOSE OF REVIEW

To review publications relating to apolipoprotein L1 (APOL1) renal risk variants published 2017.

RECENT FINDINGS

The study of APOL1 variants continues to be highly active; 24 articles published in 2017 were selected to highlight. These include clinical studies of kidney disease, kidney transplantation, hypertension, cardiovascular disease, and genetic diversity. Laboratory studies included APOL1 association with vesicle-associated membrane soluble N-ethylmaleimide-sensitive factor activating protein receptor protein and with soluble urokinase-type plasminogen activator receptor, mitochondrial dysfunction, endolysosomal dysfunction, and inflammasome activation.

SUMMARY

Our understanding of the role of APOL1 genetic variants and the mechanisms for renal toxicity continues to deepen. It is not yet clear which pathways are most relevant to human disease, and so, the most relevant drug targets remain to be defined.

African American Living Donors' Attitudes About APOL1 Genetic Testing: A Mixed Methods Study

RATIONALE & OBJECTIVE

African American live kidney donors ("donors") have a greater risk for kidney failure than European American donors. Apolipoprotein L1 gene (APOL1) variants in African Americans may be associated with this disparity.

STUDY DESIGN

Cross-sectional mixed-methods design.

SETTING & PARTICIPANTS

African American donors at 1 transplantation center.

ANALYTICAL APPROACH

Semistructured interviews assessed attitudes about APOL1 genetic testing, willingness to undergo APOL1 testing, hypothetical decisions about donating with 2 APOL1 variants, and demographics. Surveys assessed perceptions of ethnic identity and genetics knowledge. Interview transcriptions were analyzed using thematic analysis. Survey data were analyzed using descriptive statistics.

RESULTS

23 donors participated in semistructured interviews. Most (96%) reported that transplantation centers should routinely offer APOL1 genetic testing to all African American potential donors. Most (87%) would have been willing to undergo APOL1 testing before donating. Although study participants noted that APOL1 testing may deter African American potential donors from donating, most (61%) would have donated even if they had 2 high-risk APOL1 variants. Several themes emerged. Study participants believed that APOL1 testing was beneficial for providing information to help donors make informed donation decisions. Participants expressed concern about APOL1 variants placing donors at harm for kidney failure, and therefore valued taking preventive health measures. Participants believed that potential donors would experience psychological distress from learning that they have 2 gene variants and could harm their recipients. Participants were apprehensive about insurance coverage and costs of APOL1 testing and feared that APOL1 genetic test results could discriminate against African Americans.

LIMITATIONS

Findings may not be generalizable to African American potential donors.

CONCLUSIONS

Findings suggest that African American donors support APOL1 genetic testing yet fear that APOL1 variants and genetic testing could adversely affect donors' health and ethnic identity. Transplantation centers using APOL1 genetic testing should address African American donors' concerns about APOL1 genetic testing to optimize future donors' informed consent practices.

Current opinions in organ allocation

Existing methods of academic publication provide limited opportunity to obtain stakeholder input on issues of broad interest. This article reports the results of an experiment to produce a collaborative, crowdsourced article examining a current controversial issue in transplant medicine (hereby referred to as the "C4 Article"). The editorial team as a whole selected the topic of organ allocation, then divided into six sections, each supported by an individual editorial team. Widely promoted by the American Journal of Transplantation, the C4 Article was open for public comment for 1 month. The nonblinded editorial teams reviewed the contributions daily and interacted with contributors in near-real time to clarify and expand on the content received. Draft summaries of each section were posted and subsequently revised as new contributions were received. One hundred ninety-four individuals viewed the manuscript, and 107 individuals contributed to the manuscript during the submission period. The article engaged the international transplant community in producing a contemporary delineation of issues of agreement and controversy related to organ allocation and identified opportunities for new policy development. This initial experience successfully demonstrated the potential of a crowdsourced academic manuscript to advance a broad-based understanding of a complex issue.

Genetic Testing in Clinical Settings

Genetic testing is used for screening, diagnosis, and prognosis of diseases consistent with a genetic cause and to guide drug therapy to improve drug efficacy and avoid adverse effects (pharmacogenomics). This In Practice review aims to inform about DNA-related genetic test availability, interpretation, and recommended clinical actions based on results using evidence from clinical guidelines, when available. We discuss challenges that limit the widespread use of genetic information in the clinical care setting, including a small number of actionable genetic variants with strong evidence of clinical validity and utility, and the need for improving the health literacy of health care providers and the public, including for direct-to-consumer tests. Ethical, legal, and social issues and incidental findings also need to be addressed. Because our understanding of genetic factors associated with disease and drug response is rapidly increasing and new genetic tests are being developed that could be adopted by clinicians in the short term, we also provide extensive resources for information and education on genetic testing.