Rapid decline in estimated glomerular filtration rate in sickle cell anemia: results of a multicenter pooled analysis

Development of Polygenic Risk Score for Persistent Albuminuria in Children and Adults With Sickle Cell Anemia

Albuminuria is associated with high-risk apolipoprotein-L1 variants (APOL1 G1/G2) in patients with sickle cell anemia (SCA). However, this gene variant does not account for all chronic kidney disease (CKD) risk. We hypothesized that we could develop a polygenic risk score (PRS) for CKD in SCA, combining APOL1 G1/G2 with other candidate genes that modify SCA severity and further stratify patients into risk categories based on this risk score. Variants in APOL1, HMOX1 (rs743811), BCL11A (rs1424407), and α-thalassemia (α-3.7) were identified in children with SCA enrolled in the Sickle Cell Clinical Research and Intervention Program longitudinal cohort (SCCRIP). We individually tested the association of these variants with persistent albuminuria, tested a three-variant PRS (PRS-3) (APOL1, BCL11A (rs1424407), and α-3.7), and developed a four-variant PRS (PRS-4) after adding HMOX1 (rs743811) to PRS-3 using the summation of high-risk alleles. An adult SCA cohort from the University of Illinois, Chicago (UIC), was used for validation. Persistent albuminuria was defined as having a urine albumin-to-creatinine ratio (UACR) ≥ 30 mg/g on at least 2 of 3 consecutive measurements. In both cohorts, APOL1 risk variants increased the risk while α-thalassemia protected against persistent albuminuria. PRS-4 was significantly associated with persistent albuminuria (SCCRIP: p = 0.004; UIC: p = 0.00016). When stratifying patients into three and four risk categories based on the PRS, 58% and 86% of the high-risk (PRS-3) and 54% and 89% of very high-risk (PRS-4) categories developed persistent albuminuria cases in the SCCRIP and UIC cohorts, respectively. A PRS may identify high-risk SCA patients for albuminuria. Applying this PRS to guide the early implementation of disease modifiers and renoprotective therapies may help reduce the burden of SCA-related CKD. Trial Registration: NCT02098863.

U-shaped association between hemoglobin levels and albuminuria in US adults: a cross-sectional study

PURPOSE

This study aimed to explore the correlation between hemoglobin levels and albuminuria in US adults.

METHODS

This cross-sectional investigation analyzed the National Health and Nutrition Examination Survey (NHANES) information from 2011 to 2020. Data on hemoglobin, albuminuria, and other variables were collected from all participants. The logistic-regression analyses and smoothed curves were used to substantiate the research objectives.

RESULTS

The average age of the 8,868 participants was 49.5 ± 17.3 years, and 49.3% were men. The prevalence of albuminuria was 12.1%. After adjusting for potential variables in the logistic-regression analysis models, hemoglobin (per 1 g/dL increase) was inversely associated with the presence of albuminuria (odds ratio [OR], 0.92; 95% confidence interval [95%CI], 0.87-0.97). Compared with participants in quartile 3 (Q3, 14.1-15.0 g/dL) for hemoglobin levels, those in the lowest quartile 1 (Q1, 6.1-13.0 g/dL) and highest quartile 4 (Q4, 15.1-19.6 g/dL) had adjusted ORs for albuminuria of 1.48 (95% CI, 1.19-1.85) and 1.11 (95% CI, 0.9-1.38), respectively. Our observations indicated a U-shaped association between hemoglobin levels and albuminuria, with a point of inflection at approximately 15.5 g/dL. The effect sizes and CIs below and above this point were 0.853 (95% CI, 0.798-0.912) and 1.377 (95% CI, 1.055-1.797), respectively.

CONCLUSION

This study indicates that the presence of albuminuria is linked to both low and high hemoglobin levels in US adults. The management of hemoglobin may benefit kidney health.

Glomerular pressure and tubular oxygen supply: a critical dual target for renal protection

The primary treatment goal of chronic kidney disease (CKD) is preserving renal function and preventing its progression to end-stage renal disease. Glomerular hypertension and tubular hypoxia are critical risk factors in CKD progression. However, the renal hemodynamics make it difficult to avoid both factors due to the existence of peritubular capillaries that supply oxygen to the renal tubules downstream from the glomerulus through the efferent arteriole. In the treatment strategies for balancing glomerular pressure and tubular oxygen supply, afferent and efferent arterioles of the glomerulus determine glomerular filtration rate and blood flow to the peritubular capillaries. Therefore, sodium-glucose cotransporter 2 inhibitors and angiotensin receptor-neprilysin inhibitors as well as classical renin-angiotensin system inhibitors, which can change the diameter of afferent and/or efferent arterioles, are promising options for balancing this dual target and achieving renal protection. This review focuses on the clinical importance of glomerular pressure and tubular oxygen supply and proposes an effective treatment modality for this dual target.

Prevalence and associated factors of glomerular hyperfiltration among adult stable sickle cells in Kinshasa, DR Congo

INTRODUCTION

Glomerular hyperfiltration is highly frequent, theoretically dependent on cardiac output, low systemic vascular resistance and hemolysis markers. In sickle cell disease (SCD), hyperfiltration is an extremely common phenomenon and occurred in young and early adult patients. Despite the fact that the glomerular hyperfiltration is known as the early manifestations of sickle cell nephropathy, its burden among adult sickle cell disease in sub-Saharan is poor studied. This study aimed to determine the prevalence and associated factors of hyperfiltration.

METHODS

This was an analytical multicentric cross-sectional study involving stable adult sickle cell patients in Kinshasa, recruited between March and October 2023. Parameters of interest encompasses demographic, clinical, biological, echocardiographic and pulse wave measurement data. Hyperfiltration was defined using the CDK-EPI equation based on cystatin C; eGFR >130 for women and >140 ml/min/1.73m2 for men. We used multivariate logistic regression analysis to search determinants of glomerular hyperfiltration.

RESULTS

Two hundred and fourty six (246) patients with SCD were enrolled. The prevalence of hyperfiltration was 20.7%. In multiple logistic regression analysis, hyperfiltration status was independently associated with age (< 25 years) [3.57 (1.78-7.49); p = 0.027)], female sex [4.36 (2.55-5.62); p = 0.031), CRP (< 6 mg/l) [0.77 (0.61-0.97); p = 0.028)], central systolic pressure (< 100 mmHg) and central diastolic pressure (< 60 mmHg) [0.86(0.74-0.98), p = 0.028)], [(0.83 (0.71-0.98); p = 0.032)].

CONCLUSION

One out of five SS adults exhibits hyperfiltration, which is associated with young age and female sex, whereas low CRP and blood pressure were negative risk factors.

Prevalence and predictors of Sickle Cell Nephropathy A single-center experience

Sickle cell disease (SCD) is the most common monogenic disorder in Saudi Arabia, which associates with an increased risk of organs damage, including the kidney. The aim of this study is to investigate the prevalence and predictors of sickle cell nephropathy (SCN) in the Saudi population. A retrospective study was conducted from April to October 2023, and included 343 adult patients with SCD who were recruited from the hereditary blood diseases center (HBDC), Al-Ahsa, Saudi Arabia. Spot protein-to-creatinine ratio was measured and glomerular filtration rate (GFR) was estimated from serum creatinine using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. As per KIDGO guidelines, CKD was diagnosed in 93 (27.1%) patients. Based on the CKD-EPI equation, 2% of patients had low GFR (eGFR < 60mL/min), 28.3% had high GFR (eGFR > 140 mL/min), and 69.7% had normal GFR. Among SCD patients, proteinuria was observed in 26.5% of the patients. SCD patients with CKD were significantly older than non-CKD patients (p < 0.001) and had higher prevalence of diabetes mellitus (DM) and hypertension (HTN) (p = 0.045 and 0.001 respectively). The multivariate analysis showed that age (P = 0.001; OR 1.035; 95% CI 1.014-1.056) and low hemoglobin level (p = 0.034; OR -0.851; 95% CI 0.721-0.980) were independent risk factors for the development of SCN. Nephropathy is a common complication among patients with SCD as early as the third decade of life, although they remain asymptomatic. Advances in age and low hemoglobin levels are the main predictors of nephropathy. In addition, SCD patients with coexistent comorbidities, particularly DM and HTN, were at increased risk of developing kidney disease.

Challenges in predictive modelling of chronic kidney disease: A narrative review

The exponential rise in the burden of chronic kidney disease (CKD) worldwide has put enormous pressure on the economy. Predictive modeling of CKD can ease this burden by predicting the future disease occurrence ahead of its onset. There are various regression methods for predictive modeling based on the distribution of the outcome variable. However, the accuracy of the predictive model depends on how well the model is developed by taking into account the goodness of fit, choice of covariates, handling of covariates measured on a continuous scale, handling of categorical covariates, and number of outcome events per predictor parameter or sample size. Optimal performance of a predictive model on an independent cohort is desired. However, there are several challenges in the predictive modeling of CKD. Disease-specific methodological challenges hinder the development of a predictive model that is cost-effective and universally applicable to predict CKD onset. In this review, we discuss the advantages and challenges of various regression models available for predictive modeling and highlight those best for future CKD prediction.

Persistent albuminuria and chronic kidney disease in adults with sickle cell anaemia: Results from a multicenter natural history study

Clinical and laboratory correlates of chronic kidney disease (CKD) in sickle cell anaemia remain incompletely defined. In a multicenter cohort study, we evaluated the prevalence of persistent albuminuria (PA) and characteristics associated with PA, albumin-creatinine ratio (ACR) and decreased estimated glomerular filtration rate (eGFR) using logistic, linear and multinomial regression models, respectively. Of 269 participants (median age: 30 years; 57.2% females), the prevalence of PA was 35.7%. Using baseline ACR values of <100 and ≥100 mg/g, the probabilities of PA were 30.0% and 94.6%, respectively. In multivariable logistic regression analyses, male sex (β = 0.80 [SE = 0.36], p = 0.024) and ACE inhibitors/ARBs use (β = 1.54 [SE = 0.43], p < 0.001) were associated with higher likelihoods of PA, while higher haemoglobin (β = -0.33 [SE = 0.13], p = 0.009) and HbF (β = -0.04 [SE = 0.02], p = 0.041) were associated with lower likelihoods of PA. In multivariable multinomial regression analyses, older age (β = 0.06 [SE = 0.02], p = 0.004) and higher alkaline phosphatase (β = 0.01 [SE = 0.00], p = 0.004) were associated with higher odds of having eGFR 60-90 versus eGFR>90 mL/min/1.73 m2 using the cystatin C-based CKD-EPI-2012 equation. Additionally, higher systolic blood pressure (β = 0.11 [SE = 0.03], p = 0.001) and blood urea nitrogen (β = 0.45 [SE = 0.12], p < 0.001) were associated with higher odds, while higher haemoglobin (β = -1.22 [SE = 0.43], p = 0.004) was associated with lower odds of having eGFR<60 versus eGFR>90 mL/min/1.73 m2. PA and decreased eGFR are associated with measures of disease severity and comorbid conditions (Clinicaltrials.gov Identifier: NCT03277547).

Prevalence, Mortality, and Access to Care for Chronic Kidney Disease in Medicaid-Enrolled Adults With Sickle Cell Disease in California: Retrospective Cohort Study

BACKGROUND

Chronic kidney disease (CKD) is a significant complication in patients with sickle cell disease (SCD), leading to increased mortality.

OBJECTIVE

This study aims to investigate the burden of CKD in Medicaid-enrolled adults with SCD in California, examine differences in disease burden between male and female individuals, and assess mortality rates and access to specialized care.

METHODS

This retrospective cohort study used the California Sickle Cell Data Collection program to identify and monitor individuals with SCD. Medicaid claims, vital records, emergency department, and hospitalization data from 2011 to 2020 were analyzed. CKD prevalence was assessed based on ICD (International Classification of Diseases) codes, and mortality rates were calculated. Access to specialized care was examined through outpatient encounter rates with hematologists and nephrologists.

RESULTS

Among the 2345 adults with SCD, 24.4% (n=572) met the case definition for CKD. The SCD-CKD group was older at the beginning of this study (average age 44, SD 14 vs 34, SD 12.6 years) than the group without CKD. CKD prevalence increased with age, revealing significant disparities by sex. While the youngest (18-29 years) and oldest (>65 years) groups showed similar CKD prevalences between sexes (female: 12/111, 10.8% and male: 12/101, 11.9%; female: 74/147, 50.3% and male: 34/66, 51.5%, respectively), male individuals in the aged 30-59 years bracket exhibited significantly higher rates than female individuals (30-39 years: 49/294, 16.7%, P=.01; 40-49 years: 52/182, 28.6%, P=.02; and 50-59 years: 76/157,48.4%, P<.001). During this study, of the 2345 adults, 435 (18.5%) deaths occurred, predominantly within the SCD-CKD cohort (226/435, 39.5%). The median age at death was 53 (IQR 61-44) years for the SCD-CKD group compared to 43 (IQR 33-56) years for the SCD group, with male individuals in the SCD-CKD group showing significantly higher mortality rates (111/242, 45.9%; P=.009) than female individuals (115/330, 34.9%). Access to specialist care was notably limited: approximately half (281/572, 49.1%) of the SCD-CKD cohort had no hematologist visits, and 61.9% (354/572) did not see a nephrologist during this study's period.

CONCLUSIONS

This study provides robust estimates of CKD prevalence and mortality among Medicaid-enrolled adults with SCD in California. The findings highlight the need for improved access to specialized care for this population and increased awareness of the high mortality risk and progression associated with CKD.

Sickle Cell Disease and CKD: An Update

BACKGROUND

Sickle cell disease is an inherited red blood cell disorder that affects approximately 100,000 people in the USA and 25 million people worldwide. Vaso-occlusion and chronic hemolysis lead to dysfunction of vital organ systems, with the kidneys being among the most commonly affected organs.

SUMMARY

Early renal manifestations include medullary ischemia with the loss of urine-concentrating ability and hyperfiltration. This can be followed by progressive damage characterized by persistent albuminuria and a decline in the estimated glomerular filtration rate. The risk of sickle nephropathy is greater in those with the APOL1 G1 and G2 kidney risk variants and variants in HMOX1 and lower in those that coinherit α-thalassemia. Therapies to treat sickle cell disease-related kidney damage focus on sickle cell disease-modifying therapies (e.g., hydroxyurea) or those adopted from the nonsickle cell disease kidney literature (e.g., renin-angiotensin-aldosterone system inhibitors), although data on their clinical efficacy are limited to small studies with short follow-up periods. Kidney transplantation for end-stage kidney disease improves survival compared to hemodialysis but is underutilized in this patient population.

KEY MESSAGES

Kidney disease is a major contributor to early mortality, and more research is needed to understand the pathophysiology and develop targeted therapies to improve kidney health in sickle cell disease.

Urinary angiotensinogen is associated with albuminuria in adults with sickle cell anaemia

We explored the association of novel urinary biomarkers with albumin-creatinine ratio (ACR) in adults with sickle cell anaemia. Of 37 participants, 13 (35.2%) had persistent albuminuria (PA). Urinary levels of clusterin (p = 0.002), retinol-binding protein 4 (p = 0.008), alpha-1 microglobulin (p = 0.002) and angiotensinogen (p = 0.006) were significantly higher in participants with PA than in those without PA. Although univariate analysis showed significant associations between both alpha-1 microglobulin (p = 0.035) and angiotensinogen (p = 0.0021) with ACR, only angiotensinogen was associated with ACR in multivariable analysis (p = 0.04). Our results suggest that urinary angiotensinogen may identify sickle cell anaemia patients at risk for kidney disease.

Current status of the rapid decline in renal function due to diabetes mellitus and its associated factors: analysis using the National Database of Health Checkups in Japan

The increasing number of patients undergoing dialysis due to diabetes mellitus (DM) is causing serious economic problems, and its reduction is an urgent policy issue in developed countries, including Japan. We aimed to assess the association between the annual rapid decline in renal function and health checkup measures, including blood pressure, to identify health guidance targets for preventing diabetic nephropathy (DN) and diabetic kidney disease (DKD) among individuals in a medical checkup system ("Tokuteikenshin" program) in 2018. This longitudinal analysis included 3,673,829 individuals who participated in the "Tokuteikenshin" program in 2018, had hemoglobin A1c (HbA1c) levels ≥5.6%, were available for follow-up, and underwent estimated glomerular filtration rate (eGFR) evaluation. We estimated the incidence of the relative annual decrease in eGFR ≥10% per 1000 person-years and odds ratios to evaluate the rapid decline in renal function and determine health guidance goals and their role in preventing DN and DKD. Overall, 20.83% of patients with DM had a rapid decline in renal function within the observation period. A rapid decline in renal function was associated with high systolic blood pressure, poor or strict DM control, increased urinary protein excretion, and decreased blood hemoglobin levels. The incidence of rapid decline in renal function is higher in DM, and appropriate systolic blood pressure and glycemic control are important to prevent the progression to DN or DKD. Our findings will be useful for researchers, clinicians, and other public health care members in establishing effective health guidance and guidelines for CKD prevention.

Longitudinal Study of Glomerular Hyperfiltration in Adults with Sickle Cell Anemia: A Multicenter Pooled Analysis

Glomerular hyperfiltration is common in young sickle cell anemia patients and precedes development of overt kidney disease. In this multicenter pooled cohort, we characterized hyperfiltration and its decline to normal range in adult patients. Glomerular filtration rate (GFR) was estimated using the creatinine-based 2009 CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation omitting race adjustment and the 2021 CKD-EPI equation. Using CKD-EPI–2009, 506 patients had baseline estimated GFR (eGFR) ≥90 mL/min per 1.73 m², median age of 24 (interquartile range [IQR], 19-34) years and 5.17 years of follow-up. The prevalence of hyperfiltration (eGFR ≥140 and ≥130 mL/min per 1.73 m² for men and women, respectively) was 38.3%. Using CKD-EPI–2009, baseline hyperfiltration was less likely with older age (odds ratio [OR], 0.78; 95% confidence interval [CI], 0.73-0.83; P < .0001), male sex (OR, 0.32; 95% CI, 0.18-0.58; P = .0002), and higher weight (OR, 0.96; 95% CI, 0.94-0.99; P = .001). Using CKD-EPI–2021, hyperfiltration was similarly less likely with older age (OR, 0.75; 95% CI, 0.70-0.81; P < .0001), male sex (OR, 0.24; 95% CI, 0.13-0.44; P < .0001), and higher weight (OR, 0.97; 95% CI, 0.95-0.99; P = .004). In patients with baseline hyperfiltration, eGFR declined to normal values at a median age of 26.2 years. Using CKD-EPI–2009, this decline was associated with male sex (HR, 2.20; 95% CI, 1.26-3.87; P = .006), systolic blood pressure (hazard ratio [HR], 1.02; 95% CI, 1.01-1.04; P = .01), and hydroxyurea use (HR, 1.74; 95% CI, 1.002-3.03; P = .05). Using CKD-EPI–2021, decline of eGFR to normal was only associated with male sex (HR, 3.39; 95% CI, 2.01-5.69; P < .0001). Decline to normal eGFR range from hyperfiltration occurs earlier in males, those on hydroxyurea, and with higher systolic blood pressure.

The nephropathy of sickle cell trait and sickle cell disease

Sickle cell syndromes, including sickle cell disease (SCD) and sickle cell trait, are associated with multiple kidney abnormalities. Young patients with SCD have elevated effective renal plasma flow and glomerular filtration rates, which decrease to normal ranges in young adulthood and subnormal levels with advancing age. The pathophysiology of SCD-related nephropathy is multifactorial - oxidative stress, hyperfiltration and glomerular hypertension are all contributing factors. Albuminuria, which is an early clinical manifestation of glomerular damage, is common in individuals with SCD. Kidney function declines more rapidly in individuals with SCD than in those with sickle cell trait or in healthy individuals. Multiple genetic modifiers, including APOL1, HMOX1, HBA1 and HBA2 variants are also implicated in the development and progression of SCD-related nephropathy. Chronic kidney disease and rapid decline in estimated glomerular filtration rate are associated with increased mortality in adults with SCD. Renin-angiotensin-aldosterone system inhibitors are the standard of care treatment for albuminuria in SCD, despite a lack of controlled studies demonstrating their long-term efficacy. Multiple studies of novel therapeutic agents are ongoing, and patients with SCD and kidney failure should be evaluated for kidney transplantation. Given the high prevalence and severe consequences of kidney disease, additional studies are needed to elucidate the pathophysiology, natural history and treatment of SCD-related nephropathy.

Longitudinal study of glomerular hyperfiltration and normalization of estimated glomerular filtration in adults with sickle cell disease

Glomerular hyperfiltration is common in sickle cell disease (SCD) and precedes proteinuria and declining kidney function. We evaluated hyperfiltration in SCD patients and its "normalization." Routine visit data were collected retrospectively from adult SCD patients in a single centre from 2004 to 2013. Baseline was defined as first available serum creatinine and hyperfiltration as estimated glomerular filtration rates (eGFR) >130 ml/min/1·73 m² for women and >140 ml/min/1·73 m² for men. Normalization of hyperfiltration was eGFR reduction to 90-130 ml/min/1·73 m² for women or 90-140 ml/min/1·73 m² for men. Among 292 patients, median age was 27 years [interquartile range (IQR):20·0-38·0], and 56·8% had baseline hyperfiltration. Baseline hyperfiltration was inversely associated with age [odds ratio (OR):0·86, 95% confidence interval (CI): 0·82-0·90; P < 0·0001], male sex (OR:0·16, 95% CI: 0·07-0·41; P = 0·0001), haemoglobin (OR:0·76, 95% CI 0·61-0·94; P = 0·01), weight (OR:0·96, 95% CI: 0·93-0·99; P = 0·004), and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (ACE-I/ARB) use (OR:0·08, 95% CI: 0·01-0·75; P = 0·03), and positively with hydroxycarbamide use (OR:2·99, 95% CI: 1·18-7·56; P = 0·02). Of 89 hyperfiltration patients without baseline proteinuria, 10 (11·2%) developed new-onset proteinuria [median 1·05 years (IQR:0·63-2·09)]. Normalization of hyperfiltration was less likely with higher baseline eGFR [hazard ratio (HR):0·90, 95% CI: 0·86-0·95; P < 0·0001] and more likely in males (HR:6·35, 95% CI:2·71-14·86, <0·0001). Hyperfiltration is common in adult SCD patients, particularly when younger. Decline to normal values is more likely in males, possibly representing kidney function loss rather than improvement in hyperfiltration.

Outcomes of Kidney Transplant Recipients with Sickle Cell Disease: An Analysis of the 2000-2019 UNOS/OPTN Database

BACKGROUND

Lower patient survival has been observed in sickle cell disease (SCD) patients who go on to receive a kidney transplant. This study aimed to assess the post-transplant outcomes of SCD kidney transplant recipients in the contemporary era.

METHODS

We used the OPTN/UNOS database to identify first-time kidney transplant recipients from 2010 through 2019. We compared patient and allograft survival between recipients with SCD (n = 105) vs. all other diagnoses (non-SCD, n = 146,325) as the reported cause of end-stage kidney disease. We examined whether post-transplant outcomes improved among SCD in the recent era (2010-2019), compared to the early era (2000-2009).

RESULTS

After adjusting for differences in baseline characteristics, SCD was significantly associated with lower patient survival (HR 2.87; 95% CI 1.75-4.68) and death-censored graft survival (HR 1.98; 95% CI 1.30-3.01), compared to non-SCD recipients. The lower patient survival and death-censored graft survival in SCD recipients were consistently observed in comparison to outcomes of recipients with diabetes, glomerular disease, and hypertension as the cause of end-stage kidney disease. There was no significant difference in death censored graft survival (HR 0.99; 95% CI 0.51-1.73, p = 0.98) and patient survival (HR 0.93; 95% CI 0.50-1.74, p = 0.82) of SCD recipients in the recent versus early era.

CONCLUSIONS

Patient and allograft survival in SCD kidney recipients were worse than recipients with other diagnoses. Overall SCD patient and allograft outcomes in the recent era did not improve from the early era. The findings of our study should not discourage kidney transplantation for ESKD patients with SCD due to a known survival benefit of transplantation compared with remaining on dialysis. Urgent future studies are needed to identify strategies to improve patient and allograft survival in SCD kidney recipients. In addition, it may be reasonable to assign risk adjustment for SCD patients.