Genomics in the renal clinic - translating nephrogenetics for clinical practice

Shaping the future of kidney genetics in Australia: proceedings from the KidGen policy implementation workshop 2023

The KidGen Collaborative's Policy Implementation Workshop 2023 celebrated the 10th anniversary of Australia's first kidney genetics clinic in Brisbane. This event marked the establishment of a national network now comprising 19 kidney genetics clinics across Australia, all dedicated to providing equitable access to genomic testing for families affected by genetic kidney diseases. The workshop reflected on past progress and outlined future objectives for kidney genetics in Australia, recognising the collaborative efforts of clinical teams, researchers, and patients. Key insights from the workshop are documented in the proceedings.

Renal Genetics Clinic: 3-Year Experience in the Cleveland Clinic

Rationale & Objective

There has been an increasing demand for the expertise provided by a renal genetics clinic. Such programs are limited in the United States and typically operate in a genomics research setting. Here we report a 3-year, real-world, single-center renal genetics clinic experience.

Study Design

Retrospective cohort.

Setting & Participants

Outpatient cases referred to the renal genetics clinic of the Cleveland Clinic between January 2019 and March 2022 were reviewed.

Analytical Approach

Clinical and laboratory characteristics were analyzed. All genetic testing was performed in clinical labs.

Results

309 new patients referred from 15 specialties were evaluated, including 118 males and 191 females aged 35.1 ± 20.3 years. Glomerular diseases were the leading presentation followed by cystic kidney diseases, electrolyte disorders, congenital anomalies of kidneys and urinary tract, nephrolithiasis, and tubulointerstitial kidney diseases. Dysmorphic features were noted in 27 (8.7%) patients. Genetic testing was recommended in 292 (94.5%) patients including chromosomal microarray (8.9%), single-gene tests (19.5%), multigene panels (77.3%), and exome sequencing (17.5%). 80.5% of patients received insurance coverage for genetic testing. 45% (115/256) of patients had positive results, 25% (64/256) had variants of unknown significance, and 22.3% (57/256) had negative results. 43 distinct monogenic disorders were diagnosed. Family history of kidney disease was present in 52.8% of patients and associated with positive genetic findings (OR, 2.28; 95% CI, 1.40-3.74). 69% of patients with positive results received a new diagnosis and/or a change in the diagnosis. Among these, 39.7% (31/78) of patients received a significant change in disease management.

Limitations

Retrospective and single-center study.

Conclusions

The renal genetics clinic plays important roles in the diagnosis and management of patients with genetic kidney diseases. Multigene panels are the most frequently used testing modality with a high diagnostic yield. Family history of kidney disease is a strong indication for renal genetics clinic referral.

The genetic basis of congenital anomalies of the kidney and urinary tract

During the past decades, remarkable progress has been made in our understanding of the molecular basis of kidney diseases, as well as in the ability to pinpoint disease-causing genetic changes. Congenital anomalies of the kidney and urinary tract (CAKUT) are remarkably diverse, and may be either isolated to the kidney or involve other systems, and are notorious in their variable genotype-phenotype correlations. Genetic conditions underlying CAKUT are individually rare, but collectively contribute to disease etiology in ~ 16% of children with CAKUT. In this review, we will discuss basic concepts of kidney development and genetics, common causes of monogenic CAKUT, and the approach to diagnosing and managing a patient with suspected monogenic CAKUT. Altogether, the concepts presented herein represent an introduction to the emergence of nephrogenetics, a fast-growing multi-disciplinary field that is focused on deciphering the causes and manifestations of genetic kidney diseases as well as providing the framework for managing patients with genetic forms of CAKUT.

A multidisciplinary nephrogenetic referral clinic for children and adults-diagnostic achievements and insights

BACKGROUND

Genetic kidney diseases contribute a significant portion of kidney diseases in children and young adults. Nephrogenetics is a rapidly evolving subspecialty; however, in the clinical setting, increased use of genetic testing poses implementation challenges. Consequently, we established a national nephrogenetics clinic to apply a multidisciplinary model.

METHODS

Patients were referred from different pediatric or adult nephrology units across the country if their primary nephrologist suspected an undiagnosed genetic kidney disease. We determined the diagnostic rate and observed the effect of diagnosis on medical care. We also discuss the requirements of a nephrogenetics clinic in terms of logistics, recommended indications for referral, and building a multidisciplinary team.

RESULTS

Over 24 months, genetic evaluation was completed for a total of 74 unrelated probands, with an age range of 10 days to 72 years. The most common phenotypes included congenital anomalies of the kidneys and urinary tract, nephrotic syndrome or unexplained proteinuria, nephrocalcinosis/nephrolithiasis, tubulopathies, and unexplained kidney failure. Over 80% of patients were referred due to clinical suspicion of an undetermined underlying genetic diagnosis. A molecular diagnosis was reached in 42/74 probands, yielding a diagnostic rate of 57%. Of these, over 71% of diagnoses were made via next generation sequencing (gene panel or exome sequencing).

CONCLUSIONS

We identified a substantial fraction of genetic kidney etiologies among previously undiagnosed individuals which influenced subsequent clinical management. Our results support that nephrogenetics, a rapidly evolving field, may benefit from well-defined multidisciplinary co-management administered by a designated team of nephrologist, geneticist, and bioinformatician. A higher resolution version of the Graphical abstract is available as Supplementary information.

Alport syndrome and autosomal dominant tubulointerstitial kidney disease frequently underlie end stage renal disease of unknown origin - a single center analysis

BACKGROUND

The prevalence of end stage renal disease of unknown etiology in adult patients is globally high and accounts for almost 20% of all dialysis patients. Recent studies have suggested that the percentage of adult patients with a causal genetic variant has been underestimated so far. Despite severe prognostic and therapeutic implications, awareness about prevalence and manifestations of genetic kidney diseases in adult renal patients is still limited.

MATERIALS AND METHODS

We recruited 58 individuals from 39 families at our transplantation center, fulfilling at least one of the following criteria: 1) unclear etiology of kidney disease 2) clinically suspected genetic kidney disease 3) positive family history for nephropathies. The cohort consisted of patients waitlisted for kidney transplantation and patients in the follow-up after transplantation. Detailed documentation of family history and phenotype was obtained before initiating gene panel sequencing of 479 nephropathy-associated genes.

RESULTS

With this study design, a molecular genetic diagnosis was established in one third of all patients. Mutations in the collagen COL4A-genes, and mutations in MUC1 and UMOD were the most frequent among all detected causal variants. Overall, rare genetic variants were detected in more than half of all cases.

CONCLUSION

The combination of detailed phenotyping prior to NGS diagnostics was highly efficient. Elucidating the underlying genetic causes in a cohort of adult renal patients has considerable clinical impact on medical management.

Mainstreaming Genetic Testing for Adult Patients With Autosomal Dominant Polycystic Kidney Disease

PURPOSE

Genetic testing results are currently obtained approximately 1 year after referral to a medical genetics team for autosomal dominant polycystic kidney disease (ADPKD). We evaluated a mainstream genetic testing (MGT) pathway whereby the nephrology team provided pre-test counseling and selection of patients with suspected ADPKD for genetic testing prior to direct patient interaction by a medical geneticist.

SOURCES OF INFORMATION

A multidisciplinary team of nephrologists, genetic counselors, and medical geneticists developed an MGT pathway for ADPKD using current testing criteria for adult patient with suspected ADPKD and literature from MGT in oncology.

METHODS

An MGT pathway was assessed using a prospective cohort and compared to a retrospective cohort of 56 patients with ADPKD who received genetic testing using the standard, traditional pathway prior to implementing the MGT for ADPKD. The mainstream pathway was evaluated using time to diagnosis, diagnostic yield, and a patient survey to assess patient perceptions of the MGT pathway.

KEY FINDINGS

We assessed 26 patients with ADPKD using the MGT and 18 underwent genetic testing with return of results. Of them, 52 patients had data available for analysis in the traditional control cohort. The time for return of results using our MGT pathway was significantly shorter with a median time to results of 6 months compared to 12 months for the traditional pathway. We identified causative variants in 61% of patients, variants of uncertain significance in 28%, and 10% had negative testing which is in line with expectations from the literature. The patient surveys showed high satisfaction rates with the MGT pathway.

LIMITATIONS

This report is an evaluation of a new genetic testing pathway restricted to a single, publicly funded health care center. The MGT pathway involved a prospective collection of a limited number of patients with ADPKD with comparison to a retrospective cohort of patients with ADPKD evaluated by standard testing.

IMPLICATIONS

A MGT pathway using clearly defined criteria and commercially available gene panels for ADPKD can be successfully implemented in a publicly funded health care system to reduce the time required to obtain genetic results.

Clinical Utility of Genetic Testing in the Precision Diagnosis and Management of Pediatric Patients with Kidney and Urinary Tract Diseases

Background

As genetic testing increasingly integrates into the practice of nephrology, our understanding of the basis of many kidney disorders has exponentially increased. Given this, we recently initiated a Renal Genetics Clinic (RGC) at our large, urban children's hospital for patients with kidney disorders.

Methods

Genetic testing was performed in Clinical Laboratory Improvement Amendments-certified laboratories using single gene testing, multigene panels, chromosomal microarray, or exome sequencing.

Results

A total of 192 patients were evaluated in this clinic, with cystic kidney disease (49/192) being the most common reason for referral, followed by congenital anomalies of the kidney and urinary tract (41/192) and hematuria (38/192). Genetic testing was performed for 158 patients, with an overall diagnostic yield of 81 out of 158 (51%). In the 16 out of 81 (20%) of patients who reached a genetic diagnosis, medical or surgical treatment of the patients were affected, and previous clinical diagnoses were changed to more accurate genetic diagnoses in 12 of 81 (15%) patients.

Conclusions

Our genetic testing provided an accurate diagnosis for children and, in some cases, led to further diagnoses in seemingly asymptomatic family members and changes to overall medical management. Genetic testing, as facilitated by such a specialized clinical setting, thus appears to have clear utility in the diagnosis and counseling of patients with a wide range of kidney manifestations.

Genetic Testing in the Pediatric Nephrology Clinic: Understanding Families' Experiences

Genomics is rapidly being integrated into the routine care of children and families living with renal disease, principally as a diagnostic tool but also to direct therapy, identify at-risk relatives, and facilitate family planning. However, despite significant progress in understanding the genetic heterogeneity of inherited renal disease, the impact of genetic testing on parents and families of affected children is not well understood. This study aimed to investigate the experiences of families undergoing genetic testing, the psychosocial impact of receiving a genetic test result, and parent information and support needs. In-depth semistructured interviews were conducted with 26 parents of pediatric patients (<18 years of age) who had undergone genomic investigation for a suspected genetic renal disease at two tertiary pediatric nephrology services. Interviews were transcribed verbatim, coded, using NVivo software, and thematic analysis was undertaken. Key themes included emotional adjustment to a genetic diagnosis, the importance of parent-provider relationships, empowerment through social connection, and the value of family-centered care. Results highlighted the wide-ranging psychosocial impact of genetic testing on parents, as well as the importance of patient-support networks in enabling parents/families to cope and adapt. Targeted approaches to enhance communication of genetic information and the development of tailored resources to address parents' genetics and health service needs may lead to more satisfactory experiences of genetic testing.

Advances in our understanding of genetic kidney disease using kidney organoids

A significant proportion of kidney disease presenting in childhood is likely genetic in origin with a growing number of genes implicated in its development. However, many children may have changes in previously undescribed or unrecognised genes. The recent development of methods for generating human kidney organoids from human pluripotent stem cells has the potential to substantially change the rate of diagnosis and the development of new treatments for some forms of genetic kidney disease. In this review, we discuss how accurately a kidney organoid models the human kidney, identifying the strengths and weaknesses of these potentially patient-derived models of renal disease.

Toward health technology assessment of whole-genome sequencing diagnostic tests: challenges and solutions

Whole-genome sequencing (WGS) is being applied within research settings across Europe to develop genomic WGS-based diagnostic tests. The focus of this perspective paper is to describe if, and how, current approaches of health technology assessment could be applied to WGS-based diagnostic tests. This perspective draws on the collective view from a trans-European multidisciplinary consortium of methodologists, clinicians and scientists. Specific challenges can be described by using the PICO (population, intervention, comparator, outcome) framework to inform health technology assessment. Practical solutions are suggested which require joined-up, multidisciplinary working across healthcare systems using existing expert networks so that emergent issues for the health technology assessment of WGS can be met in a timely fashion.