Clinical Utility of Genetic Testing with Geographical Locations in ADPKD: Describing New Variants.

Background: Our study aims to comment on all ADPKD variants identified in our health area and explain how they are distributed geographically, to identify new variants, and relate the more frequent variants with their renal phenotype in terms of kidney survival. Materials and Methods: We identified patients suffering from ADPKD in a specialized consultation unit; genealogical trees were constructed from the proband. According to the ultrasound-defined modified Ravine-Pei criteria, relatives classified as at risk were offered participation in the genetic study. Socio-demographic, clinical, and genetic factors related to the impact of the variant on the survival of the kidney and the patient, such as age at RRT beginning and age of death, were recorded. Results: In 37 families, 33 new variants of the PKD1 gene were identified, which probably produce a truncated protein. These variants included 2 large deletions, 19 frameshifts, and 12 stop-codons, all of which had not been previously described in the databases. In 10 families, six new probably pathogenic variants in the PKD2 gene were identified. These included three substitutions; two deletions, one of which was intronic and not associated with any family; and one duplication. A total of 11 missense variants in the PKD1 gene were grouped in 14 families and classified as probably pathogenic. We found that 33 VUS were grouped into 18 families and were not described in the databases, while another 15 were without grouping, and there was only 1 in the PKD2 gene. Some of these variants were present in patients with a different pathogenic variant (described or not), and the variant was probably benign. Renal survival curves were compared to nonsense versus missense variants on the PKD1 gene to check if there were any differences. A group of 328 patients with a nonsense variant was compared with a group of 264 with a missense variant; mean renal survival for truncated variants was lower (53.1 ± 0.46 years versus non-truncated variant 59.1 ± 1.36 years; Log Rank, Breslow, and Tarone Ware, p < 0.05). Conclusions: To learn more about ADPKD, it is necessary to understand genetics. By describing new genetic variants, we are approaching creation of an accurate genetic map of the disease in our country, which could have prognostic and therapeutic implications in the future.

Identifying the main predictors of urine output in autosomal-dominant polycystic kidney disease (ADPKD) patients taking tolvaptan.

BACKGROUND: Few works have analyzed factors associated with urine output in ADPKD patients taking tolvaptan (TVP). METHODS: We selected 24-h urine samples from ADPKD patients treated with TVP. Urine osmolality/creatinine ratio was used as estimator of urinary osmolar load. RESULTS: We included 127 urine samples from 61 patients. After TVP, urine output doubled with a parallel reduction in urine solute concentration. However, when expressed as urine solute/creatinine ratios, no significant changes were observed. Daily osmolar load and osmolality/creatinine ratio did not change significantly. Before TVP, urine output was positively correlated with body weight and urine osmolality/creatinine ratio and negatively with eGFR, urine morning osmolality, and 24-h urine-calculated osmolality. After TVP, urine output was positively correlated with body weight, eGFR and negatively with age. There was a poor correlation with urine-calculated osmolality. We constructed a predictor model using mixed-effects modeling and we found that urine output was related to lower age, higher body weight, higher eGFR, and greater doses of TVP. When body weight was removed, urine output was also related to male sex and a higher daily osmolar excretion. Equation of prediction was: Urine output (mL/day) = 2771-52.9 × Age (years) + 58.4 × Weight (kg) + 18.7 × eGFR (mL/min) + 870 (if TVP = 90/30 mg) + 517 (if TVP = 60/30 mg). CONCLUSION: Patients taking TVP will undergo an increase about twice in urine production from baseline. Greater doses of TVP cause a progressive increase in urine production. GFR, age, and body weight are the main predictors of future urine output in patients taking TVP.

Erratum to: Founding mutations explains hotspots of polycystic kidney disease in Southern Spain.

[This corrects the article DOI: 10.1093/ckj/sfaa261.].

Predicting Future Renal Function Decline in Patients with Autosomal Dominant Polycystic Kidney Disease Using Mayo Clinic Classification.

INTRODUCTION: Mayo clinic classification (MCC) has been proposed in patients with autosomal dominant polycystic kidney disease (ADPKD) to identify who may experience a rapid decline of renal function. Our aim was to validate this predictive model in a population from southern Spain. METHODS: ADPKD patients with measurements of height-adjusted total kidney volume (HtTKV) and baseline estimated glomerular filtration rate (eGFR) >30 mL/min/1.73 m2 were selected. Last eGFR was estimated with Mayo Clinic (MC) equation and bias and accuracy were studied. We also analyzed predictive capacity of MCC classes using survival analysis and Cox regression models. RESULTS: We included 134 patients with a mean follow-up of 82 months. While baseline eGFR was not different between classes, last eGFR decreased significantly with them. eGFR variation rate was different according to the MCC class with a more rapid decline in 1C, 1D, and 1E classes. Final eGFR predicted was not significantly different from the real one, with an absolute bias of 0.6 ± 17.0 mL/min/1.73 m2. P10 accuracy was low ranging from 37.5 to 59.5% in classes 1C, 1D, and 1E. Using MC equation, the rate of eGFR decline was underestimated in 1C, 1D, and 1E classes. Cox regression analysis showed that MCC class is a predictor of renal survival after adjusting with baseline eGFR, age, sex, and HtTKV, with 1D and 1E classes having the worst prognosis. CONCLUSION: MCC classification is able to identify patients who will undergo a more rapid decline of renal function in a Spanish population. Prediction of future eGFR with MC equation is acceptable as a group, although it shows a loss of accuracy considering individual values. The rate of eGFR decline calculated using MC equation can underestimate the real rate presented by patients of 1C, 1D, and 1E classes.

Founding mutations explains hotspots of polycystic kidney disease in Southern Spain.

Our group identified two pathogenic variants on the PKD1 gene, c.10527_10528delGA and c.7292T>A, from unrelated families. They came from two small counties in Granada, with 61 and 26 autosomal dominant polycystic kidney disease (ADPKD) individuals affected. To determine a common ancestor, healthy and ADPKD individuals from these families were genotyped by analysing four microsatellites located on chromosome 16. Our study identified a common haplotype in all ADPKD individuals. These findings underpin our hypothesis of the founder effect and explain why there is a high frequency of ADPKD in small regions. Determining hotspots of ADPKD will help to better plan healthcare in the future.

New mutation associated with autosomal dominant polycystic kidney disease with founder effect located in the alpujarra region of granada. / Nueva mutación asociada a poliquistosis renal autosómica dominante con efecto fundador localizada en la Alpujarra de Granada.

OBJECTIVE: To demonstrate that the variant not described in PKD1 gene c.7292T> A, identified in four families from the Alpujarra in Granada, is the cause of autosomal dominant polycystic kidney disease (ADPKD). This variant consists of a transversion of thymine (T) by adenine (A) that at the level of the Polycystin 1 protein produces a change of leucine (Leu / L) by Glutamine (Gln / Q) in position 2431 (p.Leu2431Gln). METHOD: Sociodemographic and clinical variables were registered using clinical histories, genealogical trees, ultrasounds and genetic analysis to ADPKD and healthy individuals belonging to these families in the context of segregation study. RESULTS: All PKD individuals carried the c.7292T>A variant in heterozygosis, whereas healthy ones did not. Among all ADPKD patients, 62.9% were women. ADPKD diagnosis was made at 29.3 ± 15.82 years, after having the first child in 64.8%. The main reasons for diagnosis were family history and hematuria episodes. The onset of renal replacement therapy (RRT) occurred at 55.8 ± 7.62 years (range 44-67), and death at 63 ± 92.2 years (range 48-76), being the cause unknown, cardiovascular and insufficiency kidney the most frequent; the median of renal survival was established at 58.5 ± 0.77 years and the median survival of patients at 67.2 ± 3.54 years. No differences in kidney and patient survivals were observed according to sex. Among deceased patients, 52.2% required RRT and 94.4% suffered from renal failure. CONCLUSIONS: The variant c.7292T>A in PKD1 gene is responsible for the disease, and its distribution in the Alpujarra region of Granada suggests a founder effect. In ADPKD it is necessary to perform segregation studies that help us to reclassify genetic variants, in this case from indeterminate to pathogenic.

Comparison of MDRD and the old CKD-EPI equations with the new CKD-EPI equations in kidney transplant patients when glomerular filtration rate is measured with 51Cr-EDTA. / Comparación de las ecuaciones MDRD y de las antiguas ecuaciones CKD-EPI frente a las nuevas ecuaciones CKD-EPI en pacientes con trasplante renal cuando se emplea 51Cr-EDTA para medir el filtrado glomerular.

BACKGROUND: When estimating the glomerular filtration rate (GFR) in kidney transplant patients, significant differences have been found between MDRD and the 2009 CKD-EPI equations, and reference techniques. OBJECTIVE: To analyse and compare the performance of MDRD and the 2009 and 2012 CKD-EPI equations against 51Cr-EDTA plasma clearance in measuring GFR in 270 kidney transplant patients after one year. RESULTS: The mean measured GFR was 43.0±11.4 (18.2-79.4)ml/min/1.73m2, with creatinine levels of 1.42±0.46 (0.60-4.33)mg/dl and cystatin C levels of 1.45±0.53 (0.42-3.48)mg/l. This correlated moderately with creatinine (r=-0.61, P<.001) and cystatin C (r=-0.52, P<.001). Using linear regression techniques, it was found that creatinine, cystatin C, gender and age only explained 52% of GFR total variance. All equations overestimated GFR, with a mean bias of +11.1ml/min/1.73m2 for MDRD, +16.4ml/min/1.73m2 for 2009-CKD-EPI, +15ml/min/1.73m2 for CKD-EPI with cystatin C, and +14.1ml/min/1.73m2 for 2012-CKD-EPI with creatinine and cystatin C. eGFR by MDRD and the 2009 CKD-EPI equation correlated better with 51Cr-EDTA than CKD-EPI with creatinine and/or cystatin C. The overestimations were negatively correlated with creatinine and cystatin C levels, most significantly for CKD-EPI with creatinine and/or cystatin C when GFR was greater than 60ml/min/1.73m2. CONCLUSIONS: The 2012 CKD-EPI equations with creatinine and/or cystatin C significantly overestimate GFR in stage 1 and 2 chronic kidney disease. The MDRD equations is therefore recommended in these cases. The reference method used to measure GFR seems to heavily influence the bias of the equations.

Overview of autosomal dominant polycystic kidney disease in the south of Spain. / Panorámica de la poliquistosis renal autosómica dominante en una región del sur de España.

INTRODUCTION: Although autosomal dominant polycystic kidney disease is the most common hereditary kidney disease, available data tend to be limited to after initiation of renal replacement therapy. OBJECTIVE: To ascertain an overview of autosomal dominant polycystic kidney disease within the health area of Granada in southern Spain. MATERIAL AND METHODS: From January 2007 to December 2016, we collected clinical, family and demographic information about all patients with autosomal dominant polycystic kidney disease, irrespective of whether or not they were treated with RRT, in the Granada health area. The computer software SPSS 15.0 and GenoPro were used. RESULTS: 50.6% of the 1,107 diagnosed patients were men. 99.1% were Caucasian and 4-6 generations/family were studied. The geographical distribution was heterogeneous. There was no family history in 2.43%. The mean age of diagnosis was 34.0±17.80 years and the diagnosis was made after having offspring in 57.7% of cases. The main reason for diagnosis was family history (46.4%). The mean age of initiation of renal replacement therapy was 54.2±11.05 years. 96.3% of the deceased had some degree of renal failure at the time of death. The mean age of death was 60.9±14.10 years, the main cause of death being unknown in 33.5% of cases, followed by cardiovascular (27.8%). CONCLUSIONS: Cases and families were concentrated in certain geographical areas and a significant number of individuals were undiagnosed prior to cardiovascular death or diagnosed late after reproduction. Given that there is currently no curative treatment, the primary prevention strategy of preimplantation genetic diagnosis should play a leading role.

[Not Available]. / Estudio del impacto del índice de masa corporal pretrasplante sobre el pronto funcionamiento del injerto renal.

Introducción: la obesidad y el sobrepeso presentan efectos adversos sobre la salud, lo que contribuye a la aparición de enfermedades metabólicas y cardiovasculares que ponen en peligro la integridad del injerto.Objetivo: investigar la influencia del IMC pretrasplante renal sobre el funcionamiento del injerto renal al año de trasplante mediante el estudio de cuatro métodos distintos de medir la filtración glomerular.Material y métodos: en este trabajo se ha seguido a 1.336 pacientes de ambos sexos trasplantados renales; se les realizaron mediciones pretrasplante y postrasplante de parámetros bioquímicos, mediciones antropométricas y función renal mediante medidas de filtrado glomerular.Resultados: a mayor índice de masa corporal pretrasplante se produce una disminución del filtrado glomerular medido por cuatro métodos distintos, así como mayor porcentaje de rechazos.Conclusiones: un IMC elevado pretrasplante contribuye a la disfunción del injerto, a una disminución del filtrado glomerular y a complicaciones del injerto en el primer año postrasplante.

[OSTEOPOROSIS AND BODY MASS INDEX IN RENAL TRANSPLANT RECIPIENTS]. / OSTEOPOROSIS E ÍNDICE DE MASA CORPORAL EN EL TRASPLANTADO RENAL.

INTRODUCTION: frequently after kidney transplantation there is an increase in weight with a resulting high percent of obesity in these recipients. This combined with a rapid loss of bone mass, a higher prevalence of osteoporosis and fractures is evident than in normal populations. OBJECTIVES: to explore the relationship between body mass index (BMI) and prevalence of osteoporosis in a population of renal transplant recipients. METHODS: prospective longitudinal study design. The study was conducted on 306 kidney transplant recipients. The relationship between weigh and body mass index with femoral and lumbar osteopenia and osteoporosis prevalence at the moment of transplant and at 12 months post was explored. RESULTS: there was a high prevalence of overweight (35.6%) and obese (14.1%) recipients after renal transplant and 1 year after (42.2% and 24.2% respectively). Significant differences were found(p = 0.049) between the weight at the time of transplant and the presence of osteopenia or osteoporosis at the lumbar level one year after, the highest weights were in recipients with osteoporosis. The mean BMI was higher (p = 0.028) in osteoporotic patients (26.59 kg/m2) than in patients with osteopenia (24.23 kg/m2). CONCLUSION: results seem to be consistent with recent studies in the general population showing excessive weight as a possible factor detrimental to the bone health.

Introducción y objetivos: tras el trasplante renal es frecuente un aumento de peso, así como un elevado porcentaje de obesidad en estos pacientes. Por otro lado, tras el trasplante se produce una pérdida de la masa ósea, siendo la prevalencia de osteoporosis y fracturas óseas mayor que en la población general. Objetivos: explorar la relación entre el índice de masa corporal y la prevalencia de osteopenia y osteoporosis en una población de trasplantados renales. Material y método: estudio longitudinal prospectivo sobre una muestra de 306 trasplantados renales. Se exploraron las relaciones entre el peso y el índice de masa corporal con la prevalencia de osteopenia y osteoporosis a nivel femoral y lumbar en el momento del trasplante y a los 12 meses del mismo. Resultados: se halló una alta prevalencia de sobrepeso (35,6%) y obesidad (14,1%) tras el trasplante renal y al año del mismo (42,2% y 24,2%, respectivamente). Se hallaron diferencias estadísticamente significativas (p = 0,049) entre el peso en el momento del trasplante y la presencia de osteopenia u osteoporosis al año del mismo a nivel lumbar, siendo el peso medio más elevado entre los pacientes con osteoporosis. La media del IMC fue más elevada (p = 0,028) en los pacientes osteoporóticos (26,59 kg/m2) que en los pacientes con osteopenia (24,23 kg/m2). Conclusiones: nuestros resultados parecen estar en concordancia con recientes estudios realizados en la población general, que muestran el sobrepeso como un posible factor perjudicial para el hueso.