Hydroxyurea treatment decreases glomerular hyperfiltration in children with sickle cell anemia

Hydroxyurea mobile directly observed therapy versus standard monitoring in patients with sickle cell anemia: a phase 2 randomized trial

BACKGROUND

Sickle cell anemia (SCA) prevalence remains high in sub-Saharan Africa. Long-term treatment with hydroxyurea (HU) increases survival, however, poor adherence to treatment could limit effectiveness. Whilst HU treatment adherence is currently high, this might decrease over time.

METHODS

We conducted a single-center, randomized, open-label, parallel group phase 2 controlled clinical trial to determine whether mobile Directly Observed Therapy (m-DOT) increases HU treatment adherence (NCT02844673). Eligible participants were adults with homozygous SCA. People on a chronic blood transfusion program, with hemoglobin (Hb) A levels greater than 20% of the total Hb, total Hb less than 4 g/dL, pregnant or HIV positive were excluded. After a 3-month pre-treatment period participants were randomized to either m-DOT or standard monitoring arm. All participants received smart mobile phones and were treated with HU (15 mg/kg) daily for three months. In the m-DOT arm, drug intake was video recorded on cell phone by the participant and the video sent to the study team. The primary objective was to evaluate the effect of m-DOT on adherence to HU treatment by medication possession ratio (MPR).

RESULTS

Of the 86 participants randomized, 76 completed the trial (26.13 ± 6.97 years, 63.5 % female). Adherence was high (MPR > 95 %) in both groups, 29 (80.6 %) in m-DOT versus 37 (94.9 %) in the standard monitoring arm (P = 0.079). No HU treatment was withheld from participants due to safety concerns.

CONCLUSIONS

m-DOT did not increase adherence to HU treatment. We recommend that further testing in larger trials with a longer follow up period be undertaken.

Hydroxyurea dose optimisation for children with sickle cell anaemia in sub-Saharan Africa (REACH): extended follow-up of a multicentre, open-label, phase 1/2 trial

BACKGROUND

Realizing Effectiveness Across Continents with Hydroxyurea (REACH) is an open-label non-randomised trial of hydroxyurea (hydroxycarbamide) in children with sickle cell anaemia in sub-Saharan Africa. The short-term results of REACH on safety, feasibility, and effectiveness of hydroxyurea were published previously. In this paper we report results from extended hydroxyurea treatment in the REACH cohort up to 8 years.

METHODS

In this open-label, non-randomised, phase 1/2 trial, participants were recruited from four clinical sites in Kilifi, Kenya; Mbale, Uganda; Luanda, Angola; and Kinshasa, Democratic Republic of Congo. Eligible children were 1-10 years old with documented haemoglobin SS or haemoglobin Sβ zero thalassaemia, weighing at least 10 kg. Participants received fixed-dose hydroxyurea of 17.5 (±2.5) mg/kg per day for 6 months (fixed-dose phase), followed by 6 months of dose escalation (2·5-5·0 mg/kg increments every 8 weeks) as tolerated, up to 20-35 mg/kg per day (maximum tolerated dose; MTD), defined as mild myelosuppression. After the MTD was reached, hydroxyurea dosing was optimised for each participant on the basis of changes in bodyweight and laboratory values over time (MTD with optimisation phase). After completion of the first 12 months, children with an acceptable toxicity profile and favourable responses were given the opportunity to continue hydroxyurea until the age of 18 years. The safety and feasibility results after 3 years has been reported previously. Here, haematological responses, clinical events, and toxicity rates were compared across the dosing phases (fixed-dose hydroxyurea vs MTD with optimisation phase) as protocol-specified outcomes. REACH is registered on ClinicalTrials.gov (NCT01966731) and is ongoing.

FINDINGS

We enrolled 635 children between July 4, 2014, and Nov 11, 2016. 606 children were given hydroxyurea and 522 (86%; 266 [51%] boys and 256 [49%] girls) received treatment for a median of 93 months (IQR 84-97) with 4340 patient-years of treatment. The current (Oct 5, 2023) mean dose is 28·2 (SD 5·2) mg/kg per day with an increased mean haemoglobin concentration (7·3 [SD 1·1] g/dL at baseline to 8·5 [1·5] g/dL) and mean fetal haemoglobin level (10·9% [SD 6·8] to 23·3% [9·5]) and decreased absolute neutrophil count (6·8 [3·0] × 109 cells per L to 3·6 [2·2] × 109 cells per L). Incidence rate ratios (IRR) comparing MTD with fixed-dose hydroxyurea indicate decreased vaso-occlusive episodes (0·60; 95% CI 0·52-0·70; p<0·0001), acute chest syndrome events (0·21; 0·13-0·33; p<0·0001), recurrent stroke events (0·27; 0·07-1·06; p=0·061), malaria infections (0·58; 0·46-0·72; p<0·0001), non-malarial infections (0·52; 0·46-0·58; p<0·0001), serious adverse events (0·42; 0·27-0·67; p<0·0001), and death (0·70; 0·25-1·97; p=0·50). Dose-limiting toxicity rates were similar between the fixed-dose (24·1 per 100 patient-years) and MTD phases (23·2 per 100 patient-years; 0·97; 0·70-1·35; p=0·86). Grade 3 and 4 adverse events were infrequent (18·5 per 100 patient-years) and included malaria infection, non-malarial infections, vaso-occlusive pain, and acute chest syndrome. Serious adverse events were uncommon (3·6 per 100 patient-years) and included malaria infections, parvovirus-associated anaemia, sepsis, and stroke, with no treatment-related deaths.

INTERPRETATION

Hydroxyurea dose escalation to MTD with dose optimisation significantly improved clinical responses and treatment outcomes, without increasing toxicities in children with sickle cell anaemia in sub-Saharan Africa.

FUNDING

US National Heart, Lung, and Blood Institute and Cincinnati Children's Research Foundation.

Acute kidney injury is more common in hospitalised children with sickle cell anaemia in Africa

AIM

To document the prevalence, severity, hospital outcome and factors associated with acute kidney injury (AKI) in hospitalised children with sickle cell anaemia (SCA).

METHODS

In this prospective observational study involving children aged 0.5-17 years with SCA requiring hospitalisation, we used serum creatinine level at 0 and 48 h of hospitalisation to determine the presence of AKI.

RESULTS

The study involved 155 children with SCA aged 0.5-17 years with a median (interquartile range) age of 7.8 (4.3-11.0) years. Acute kidney injury occurred in 27 (17.4%) children with 33.3% reaching stage 3. Hepatomegaly (81.5% vs. 55.4%; p = 0.015), splenomegaly (33.3% vs. 10.9%; p = 0.003), dipstick proteinuria (22.2% vs. 5.4%; p = 0.004), and hematuria (29.6% vs. 3.1%; p = <0.001) were more common in those with AKI. In contrast, children with AKI had lower haematocrit (16.9% vs. 22.2%; p = <0.001) and serum bicarbonate (16.7 vs. 19.1 mmoL/L; p = 0.010) compared with those without AKI. Those with AKI had longer hospital stay (median [interquartile range]: 7 [4-12] days vs. 4 [3-6] days; p = 0.008).

CONCLUSION

AKI is common among hospitalised children with AKI and is associated with longer hospital stay.

Role of hydroxyurea therapy in the prevention of organ damage in sickle cell disease: a systematic review and meta-analysis

BACKGROUND

Hydroxyurea is an affordable drug that reduces vaso-occlusive crises and transfusion requirements in sickle cell disease. However, its effectiveness in preventing chronic organ damage is still unclear. This systematic review and meta-analysis aimed to evaluate the role of hydroxyurea in preventing organ morbidity.

METHOD

We included original articles published in English from 1st January 1990 to 31st January 2023, reporting hydroxyurea therapy and organ damage from PubMed, Google Scholar, Scopus, and CrossRef databases. A total of 45 studies with 4681 sickle cell disease patients were evaluated for organ damage.

RESULTS

Our analysis showed that hydroxyurea intervention significantly lowered transcranial Doppler and tricuspid regurgitant velocity, with a standardized mean difference of - 1.03 (- 1.49; - 0.58); I 2 = 96% and - 1.37 (CI - 2.31, - 0.42); I 2 = 94%, respectively. Moreover, the pooled estimate for albuminuria showed a beneficial effect post-hydroxyurea therapy by reducing the risk of albuminuria by 58% (risk ratio of 0.42 (0.28; 0.63); I 2 = 28%).

CONCLUSION

Our study found that a hydroxyurea dose above 20 mg/kg/day with a mean rise in HbF by 18.46% post-hydroxyurea therapy had a beneficial role in reducing transcranial doppler velocity, tricuspid regurgitant velocity, albuminuria, and splenic abnormality.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42023401187.

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.

Interventions for chronic kidney disease in people with sickle cell disease

BACKGROUND

Sickle cell disease (SCD), one of the commonest severe monogenic disorders, is caused by the inheritance of two abnormal haemoglobin (beta-globin) genes. SCD can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Kidney disease is a frequent and potentially severe complication in people with SCD. Chronic kidney disease (CKD) is defined as abnormalities of kidney structure or function present for more than three months. Sickle cell nephropathy refers to the spectrum of kidney complications in SCD. Glomerular damage is a cause of microalbuminuria and can develop at an early age in children with SCD, with increased prevalence in adulthood. In people with sickle cell nephropathy, outcomes are poor as a result of the progression to proteinuria and chronic kidney insufficiency. Up to 12% of people who develop sickle cell nephropathy will develop end-stage renal disease. This is an update of a review first published in 2017.

OBJECTIVES

To assess the effectiveness of any intervention for preventing or reducing kidney complications or chronic kidney disease in people with sickle cell disease. Possible interventions include red blood cell transfusions, hydroxyurea, and angiotensin-converting enzyme inhibitors (ACEIs), either alone or in combination.

SEARCH METHODS

We searched for relevant trials in the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register, CENTRAL, MEDLINE, Embase, seven other databases, and two other trials registers.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing interventions to prevent or reduce kidney complications or CKD in people with SCD. We applied no restrictions related to outcomes examined, language, or publication status.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility, extracted data, assessed the risk of bias, and assessed the certainty of the evidence (GRADE).

MAIN RESULTS

We included three RCTs with 385 participants. We rated the certainty of the evidence as low to very low across different outcomes according to GRADE methodology, downgrading for risk of bias concerns, indirectness, and imprecision. Hydroxyurea versus placebo One RCT published in 2011 compared hydroxyurea to placebo in 193 children aged nine to 18 months. We are unsure if hydroxyurea compared to placebo reduces or prevents progression of kidney disease assessed by change in glomerular filtration rate (mean difference (MD) 0.58 mL/min /1.73 m2, 95% confidence interval (CI) -14.60 to 15.76; 142 participants; very low certainty). Hydroxyurea compared to placebo may improve the ability to concentrate urine (MD 42.23 mOsm/kg, 95% CI 12.14 to 72.32; 178 participants; low certainty), and may make little or no difference to SCD-related serious adverse events, including acute chest syndrome (risk ratio (RR) 0.39, 99% CI 0.13 to 1.16; 193 participants; low certainty), painful crisis (RR 0.68, 99% CI 0.45 to 1.02; 193 participants; low certainty); and hospitalisations (RR 0.83, 99% CI 0.68 to 1.01; 193 participants; low certainty). No deaths occurred in either trial arm and the RCT did not report quality of life. Angiotensin-converting enzyme inhibitors versus placebo One RCT published in 1998 compared an ACEI (captopril) to placebo in 22 adults with normal blood pressure and microalbuminuria. We are unsure if captopril compared to placebo reduces proteinuria (MD -49.00 mg/day, 95% CI -124.10 to 26.10; 22 participants; very low certainty). We are unsure if captopril reduces or prevents kidney disease as measured by creatinine clearance; the trial authors stated that creatinine clearance remained constant over six months in both groups, but provided no comparative data (very low certainty). The RCT did not report serious adverse events, all-cause mortality, or quality of life. Angiotensin-converting enzyme inhibitors versus vitamin C One RCT published in 2020 compared an ACEI (lisinopril) with vitamin C in 170 children aged one to 18 years with normal blood pressure and microalbuminuria. It reported no data we could analyse. We are unsure if lisinopril compared to vitamin C reduces proteinuria in this population: the large drop in microalbuminuria in both arms of the trial after only one month on treatment may have been due to an overestimation of microalbuminuria at baseline rather than a true effect. The RCT did not report serious adverse events, all-cause mortality, or quality of life.

AUTHORS' CONCLUSIONS

We are unsure if hydroxyurea improves glomerular filtration rate or reduces hyperfiltration in children aged nine to 18 months, but it may improve their ability to concentrate urine and may make little or no difference to the incidence of acute chest syndrome, painful crises, and hospitalisations. We are unsure if ACEI compared to placebo has any effect on preventing or reducing kidney complications in adults with normal blood pressure and microalbuminuria. We are unsure if ACEI compared to vitamin C has any effect on preventing or reducing kidney complications in children with normal blood pressure and microalbuminuria. No RCTs assessed red blood cell transfusions or any combined interventions to prevent or reduce kidney complications. Due to lack of evidence, we cannot comment on the management of children aged over 18 months or adults with any known genotype of SCD. We have identified a lack of adequately designed and powered studies, although we found four ongoing trials since the last version of this review. Only one ongoing trial addresses renal function as a primary outcome in the short term, but such interventions have long-term effects. Trials of hydroxyurea, ACEIs or red blood cell transfusion in older children and adults are urgently needed to determine any effect on prevention or reduction of kidney complications in people with SCD.

Glomerular hyperfiltration: part 2-clinical significance in children

Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.

Emerging Therapies and Advances in Sickle Cell Disease with a Focus on Renal Manifestations

The underlying mechanisms of disease in sickle cell disease (SCD) contribute to a multifaceted nephropathy, commonly manifested as albuminuria. In severe SCD genotypes ( e.g. , Hemoglobin SS [HbSS]), albuminuria and CKD are major predictors of mortality in this population. Therefore, the monitoring and management of renal function is an intrinsic part of comprehensive care in SCD. Management of nephropathy in SCD can be accomplished with SCD-directed therapies and/or CKD-directed therapies. In the past 5 years, novel disease-modifying and palliative therapies have been approved in SCD to target aspects of the disease, such as anemia, inflammation, and vasculopathy. Along with conventional hydroxyurea and chronic transfusion, l -glutamine, crizanlizumab, and voxelotor have all been shown to mitigate some adverse effect of SCD, and their effect on nephropathy is being investigated. CKD-directed therapies such as renin-angiotensin-aldosterone system blockers have long been used in SCD nephropathy; however, more complete long-term studies on benefits are needed. Given the effect of renal disease on survival, further assessment of the mechanisms and efficacy of these SCD-directed or CKD-directed therapeutic agents is essential.

Hemolysis scavenger proteins and renal function marker in children with sickle cell disease at steady state: A cross-sectional study

Background and Aims

Hemolysis is a fundamental feature of sickle cell disease (SCD) contributing to the vaso-occlusive crisis of patients. The objectives of the study were to assess the link between hemolysis proteins and hematological parameters, and to validate cystatin C (CYS C) as a potent renal marker in diagnoising SCD.

Method

Here, a cross-sectional study carried out at the pediatric SCD clinic of the Komfo Anokye Teaching Hospital comprised 90 SCD children (HbSC, HbSF, and HbSS). ANOVA, t-test, and Spearman's rank correlation analysis were done. Elevated proteins levels were compared to standard values; alpha-1 microglobulin (A1M) (1.8-65 µg/L), CYS C (0.1-4.5 µmol/L), and haemopexin (HPX) (500-1500 µg/mL).

Results

The mean (standard deviation) age of participants was 9.830 (±0.3217) years, and 46% of them were males. From simple descriptive analysis, we observed that all but one patient had their HPX level below the reference range (<500 µg/mL). Here, A1M levels were shown to be within the appropriate reference range for all the patients except few patients. CYS C levels were also all within the required reference values. A Spearman's rank correlation test between full blood count and HPX generally suggested a weak but positive correlation; RBC (coef. = 0.2448; p = 0.0248), HGB (coef. = 0.2310; p = 0.030), hematocrit (coef. = 0.2509; p = 0.020), and platelet (coef. = 0.1545; p = 0.160). Mean corpuscular volume (coef. = -0.5645; p = 0.610) had a stronger but negative correlation with HPX. This study depicts a positive and stronger association between CYS C and HPX levels (coef. = 0.9996; p < 0.0001), validating the use of CYS C as a useful marker of renal function in persons with SCDs.

Conclusion

In the present study, we show that A1M levels were normal for most of the patients, hence CYS C levels are not alarming in this study. Further, there exists a correlation between hemolysis scavenger proteins and hematological parameters.

Glomerular filtration rate abnormalities in sickle cell disease

Sickle cell disease (SCD) is a group of inherited blood disorders affecting the β-globin gene, resulting in the polymerization of hemoglobin and subsequent sickling of the red blood cell. Renal disease, the most common complication in SCD, begins in childhood with glomerular hyperfiltration and then progresses into albuminuria, a fast decline of glomerular filtration, and renal failure in adults. This mini-review focuses on glomerular filtration abnormalities and the mechanisms of hyperfiltration, explores genetic modifiers and methods of estimating glomerular filtration rates, and examines novel biomarkers of glomerular filtration in SCD.

Sickle Cell Disease in Children and Adolescents: A Review of the Historical, Clinical, and Public Health Perspective of Sub-Saharan Africa and Beyond

Sickle cell disease (SCD) is an umbrella term for a group of life-long debilitating autosomal recessive disorders that are caused by a single-point mutation (Glu→Val) that results in polymerization of hemoglobin (Hb) and reversible sickle-shape deformation of erythrocytes. This leads to increased hemolysis of erythrocytes and microvascular occlusion, ischemia-reperfusion injury, and tissue infarction, ultimately causing multisystem end-organ complications. Sickle cell anemia (HbSS) is the most common and most severe genotype of SCD, followed by HbSC, HbSβ⁰thalassemia, HbSβ+thalassemia, and rare and benign genotypes. Clinical manifestations of SCD occur early in life, are variable, and are modified by several genetic and environmental factors. Nearly 500 children with SCD continue to die prematurely every day, due to delayed diagnosis and/or lack of access to comprehensive care in sub-Saharan Africa (SSA), a trend that needs to be urgently reversed. Despite proven efficacy in developed countries, newborn screening programs are not universal in SSA. This calls for a consolidated effort to make this possible, through the use of rapid, accurate, and cheap point-of-care test kits which require minimal training. For almost two decades, hydroxyurea (hydroxycarbamide), a century-old drug, was the only disease-modifying therapy approved by the U.S. Food and Drug Administration. Recently, the list expanded to L-glutamine, crizanlizumab, and voxelotor, with several promising novel therapies in the pipeline. Despite its several limitations, hematopoietic stem cell transplant (HSCT) remains the only curative intervention for SCD. Meanwhile, recent advances in gene therapy trials offer a glimpse of hope for the near future, although its use maybe limited to developed countries for several decades.

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.

Sickle Cell Disease and Kidney

Sickle cell disease causes several kidney manifestations. They include defects in urine concentration, impaired handling of potassium and hydrogen ion, albuminuria, acute kidney injury, and chronic kidney disease to name a few. Glomerular hyperfiltration, tubular hyperfunctioning, endothelial damage from repeated sickling and vaso-occlusive episodes, and iron-induced proinflammatory changes in the glomerular mesangium and tubulointerstitium are some of the mechanisms of kidney damage. Albuminuria is one of the most and common clinical features of kidney disease and progresses with age. Kidney disease in patients with sickle cell is associated with increased mortality. Annual screening for proteinuria starting at age 10 years and limiting the use of nonsteroidal anti-inflammatory agents and the use of angiotensin-converting enzyme inhibitors may help in early detection and delaying the progression of kidney disease. Adequate hydration, angiotensin-converting enzyme inhibitors, and adequate control of sickle cell are the main stay of treatment for albuminuria. The hemoglobin goal for patients with sickle cell nephropathy is lesser (10 g/dL) than that for patients with chronic kidney disease due to other causes given that a higher hemoglobin level increases viscosity and the risk of precipitating vaso-occlusive episodes. A multidisciplinary approach is recommended for managing patients with sickle cell and kidney diseases.

Hemodynamic and biological correlates of glomerular hyperfiltration in sickle cell patients before and under renin-angiotensin system blocker

Glomerular hyperfiltration alone or associated with albuminuria is a well-known feature of sickle cell associated nephropathy. Though, glomerular hyperfiltration is currently considered to be related to a high renal plasma flow and chronic hemolysis, cardiac output influence on measured glomerular filtration rate (mGFR) have not been investigated so far. Thirty seven homozygous sickle cell patients (SCA) from the RAND study investigated before and under angiotensin converting enzyme inhibitor (ACEI) were included. Both mGFR and cardiac index (CI) were high (> 110 ml/min/1.73 m² and > 3.5 l/m² in 81% and 97% of cases) with low systemic vascular resistance (SVR) (< 700 dynes/s/cm^-5) in 38% of cases. mGFR association with CI and SVR were significant at baseline (respectively ρ: 0.44, p = 0.008 and ρ: - 0.37, p = 0.02) and under ACEI (p = 0.007 and 0.01 respectively), in accordance with previous data showing that hyperfiltration was linked to an increased glomerular perfusion and a glomerulomegaly rather than increased capillary hydrostatic pressure. Of notice, after adjustment on CI, mGFR remained associated with reticulocyte count and albuminuria under ACEI (p = 0.006 and 0.02 respectively). Our results suggest that hyperfiltration is tightly linked to an increased cardiac output which may account for an increased renal blood flow. Chronic hemolysis could be a relevant factor accounting for hyperfiltration potentially acting on glomerular enlargement which appears as a key factor. Our data suggest that cardiac output assessment is a relevant tool in the routine management and monitoring of SCA nephropathy.

Chronic organ injuries in children with sickle cell disease

Median life expectancy of patients with sickle cell disease has increased to up to 55 years but there are still frequent cases of premature death, mostly in patients with pre-existing organ failure such as pulmonary hypertension, kidney injury, and cerebral vasculopathy. Most organ injuries remain asymptomatic for a long time and can only be detected through early systematic screening. Protocols combining assessment of velocities on transcranial Doppler and regular transfusions in patients with abnormal velocities have been demonstrated to dramatically reduce the risk of stroke. In contrast, no consensus has been reached on systematic screening or therapy for silent cerebral infarcts. The prognostic significance of increased tricuspid regurgitant jet velocity on echocardiography has not yet been identified in children, whereas increased albuminuria is a good predictor of kidney injury. Finally, screening for hip and eye disorder is recommended; however, different countries adopt different screening strategies. Hydroxyurea is probably of potential benefit in preventing chronic organ damage but this requires further study in order to be fully demonstrated. Efficacy and safety of the other new drugs available are also under investigation.

Population Pharmacokinetic Analysis of Rivipansel in Healthy Subjects and Subjects with Sickle Cell Disease

Background

Sickle cell disease is an inherited blood disorder with reduced blood-carrying capacity. It is associated with a tendency to form microclots in blood vessels, leading to painful episodes known as a vaso-occlusive crisis. Rivipansel is a pan-selectin inhibitor being studied for the treatment of a vaso-occlusive crisis in patients with sickle cell disease.

Methods

A population pharmacokinetic model of rivipansel plasma and urine concentrations was constructed using a two-compartment model and data from nine different clinical studies. Creatinine clearance was calculated using the Schwartz formula for children and the Chronic Kidney Disease Epidemiology Collaboration formula for adults. Urine volume and concentration of the study drug in urine from subjects in five clinical studies were used to estimate renal and nonrenal clearance.

Results

Rivipansel drug concentrations were well described by the model. The post hoc estimates of average steady-state concentrations were predicted to be similar for the adult and pediatric cohorts of the pivotal phase III study. Parameter estimates showed almost exclusively renal excretion of rivipansel, which is consistent with the known properties of the drug.

Conclusions

The pharmacokinetics of rivipansel was well characterized by a two-compartment population pharmacokinetic model. Our results illustrate the important role of simulations in optimizing a potential drug dosing regimen for patients with sickle cell disease and progressive renal impairment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40268-021-00346-3.

Progression of albuminuria in patients with sickle cell anemia: a multicenter, longitudinal study

Sickle cell nephropathy results in chronic kidney disease (CKD), which is associated with significant morbidity and mortality in sickle cell anemia (SCA). Albuminuria is an early manifestation of sickle nephropathy; however, little is known about progression of albuminuria or its correlation with glomerular filtration rate (GFR) decline or CKD. We studied nephropathy progression in 303 SCA participants in a prospective, multicenter, longitudinal study. We collected steady-state urine and serum samples yearly and assessed albumin/creatinine ratio (ACR), estimated GFR (eGFR), and SCA and nephropathy biomarkers. Participants with albuminuria (ACR ≥30 mg/g) for ≥2 annual measurements were classified as having persistent albuminuria (PA). At baseline (mean age, 21 years; range, 2-64 years), 32% had albuminuria. In longitudinal multivariate analysis, ACR was associated with sex, anemia, older age, and higher bilirubin and kidney injury molecule-1 levels. Albuminuria increased with age by 3.5 mg/g per year (P < .0001). Of 175 participants with ≥3 annual samples, 81% with baseline albuminuria ≥100 mg/g developed PA. Decreased eGFR and adult CKD were associated with PA (P = .002 and P = .02, respectively), but not with baseline albuminuria. Rate of eGFR decline was steeper among adults (but not children) with albuminuria, compared with those without (P = .02). Participants with PA were more likely to have rapid eGFR decline compared with those without (P = .03). In this longitudinal study, albuminuria progressed with age, and adults with albuminuria had worse eGFR decline than those without. Albuminuria ≥100 mg/g predicted PA, which was associated with rapid eGFR decline and CKD development in adults with SCA. This trial was registered at www.clinicaltrials.gov as #NCT02239016.

Nephrotic syndrome on sickle cell disease: the impact of Hydroxyurea

Nephropathy is a common under-recognised complication of sickle cell disease (SCD) and one of the main factors of poor prognosis in these patients. The association between nephrotic syndrome and SCD in children is rare. Strategies for sickle cell nephropathy prevention are still poorly established. Blood pressure control as well as monitoring of microalbuminuria and renal function are mandatory. The use of antiproteinuric drugs, such as anti-ACE inhibitors (ACEis) and hydroxyurea, should be considered in early stages. Here, we report a case of a female adolescent with SCD and inaugural nephrotic syndrome who, after an initial treatment failure with corticotherapy, had a remarkable recovery after treatment with hydroxyurea and ACEis.

Use of Wise Device Technology to Measure Adherence to Hydroxyurea Therapy in Youth With Sickle Cell Disease

Despite broad support for hydroxyurea (HU) therapy, suboptimal adherence is reported for youth with sickle cell disease. Valid adherence measurement is crucial to understanding the relationship between medication behavior, disease response, and patient-centered health outcomes. The current pilot study examined the feasibility of the Wise electronic device for longitudinal HU adherence measurement in a sample of 36 youths prescribed HU. The study also explored the association between HU adherence, as measured by the Wise device, with other adherence measures (ie, family report, lab values, pill count, and medication possession ratio). A measure of family-reported acceptability was also completed. Overall, results supported the feasibility of the Wise device (rate of consent=82%, device use=75%, device failure=3%) for HU adherence measurement and most families rated their experience using their device positively (favorable responses ranged from 67% to 100%). Associations between HU adherence, as measured by the Wise device, and other adherence measures were not significant. Overall, the feasibility was supported. The Wise device allows longitudinal measurement of adherence with HU from initiation as a young child (ie, with liquid formulations) through adolescence and provides a novel means of adherence measurement for both clinical and research use.

Proteinuric and nonproteinuric chronic kidney disease among patients with sickle cell anaemia (HbSS) attending a tertiary hospital in north-eastern Nigeria

OBJECTIVE/BACKGROUND

Individuals with sickle cell anaemia (SCA) may manifest various forms of renal abnormalities. Proteinuria is an early marker of renal dysfunction and a strong risk factor for chronic kidney disease (CKD) progression in both patients with SCA and non-SCA population. Currently, the degree of attention given to proteinuric CKD far exceeds that of nonproteinuric CKD, and risk factors that might trigger a progressive decline of the glomerular filtration rate (GFR) in the absence of proteinuria have not been well evaluated in SCA. The aim of this study was to compare the clinical and laboratory parameters among SCA patients with proteinuric and nonproteinuric CKD.

METHODS

This was a cross-sectional study conducted at the University of Maiduguri Teaching Hospital in north-eastern Nigeria between January 2013 and April 2018. Clinical variables including age of diagnosis of SCA, frequency of vaso-occlusive crises, number of hospitalizations per annum and transfusion therapy were collected. Laboratory data including haematological profile and renal function test were obtained from routine blood sampling.

RESULTS

A total of 257 patients with SCA (HbSS) were enrolled during the study period of which 42 had proteinuric CKD, and 48 had nonproteinuric CKD. The two groups were matched for the number of hospital admission (p = .063) and blood transfusion per year (p = .450), frequency of painful crisis (p = .210), systolic blood pressure (p = .084) and diastolic blood pressure (p = .400). In the proteinuric CKD group, the mean serum creatinine was higher (332.17 µmol/L, p = .001) and the estimated GFR was lower (31.88 mL/min, p = .046). The serum alkaline phosphatase was higher in the nonproteinuric CKD group (81.81 IU/L, p = .012).

CONCLUSION

Nonproteinuric CKD was more frequent than proteinuric CKD in our study population; however, the proteinuric group presented with more advanced disease.

End points for sickle cell disease clinical trials: renal and cardiopulmonary, cure, and low-resource settings

To address the global burden of sickle cell disease and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to patient-reported outcome, pain (non-patient-reported outcomes), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the end-organ considerations, measurement of cure, and low-resource settings panels as well as relevant findings and recommendations from the biomarkers panel.

Outcomes following kidney transplantation in patients with sickle cell disease: The impact of automated exchange blood transfusion

There are over 12,000 people with sickle cell disease (SCD) in the UK, and 4-12% of patients who develop Sickle Cell Nephropathy (SCN) progress to End Stage Renal Disease (ESRD). Renal transplantation offers the best outcomes for these patients with but their access to transplantation is often limited. Regular automated exchange blood transfusions (EBT) reduce the complications of SCD and may improve outcomes. However, concerns over alloimmunisation limit its widespread implementation. In this retrospective multicenter study, data were collected on 34 SCD patients who received a kidney transplant across 6 London Hospitals between 1997 and 2017. 20/34 patients were on an EBT program, pre or post renal transplantation. Overall patient and graft survival were inferior to contemporaneous UK data in the ESRD population as a whole, a finding which is well-recognised. However, patient survival (CI 95%, p = 0.0032), graft survival and graft function were superior at all time-points in those who received EBT versus those who did not. 4/20 patients (20%) on EBT developed de novo donor specific antibodies (DSAs). 3/14 patients (21%) not on EBT developed de novo DSAs. The incidence of rejection in those on EBT was 5/18 (28%), as compared with 7/13 (54%) not on EBT. In conclusion, our data, while limited by an inevitably small sample size and differences in the date of transplantation, do suggest that long-term automated EBT post renal transplant is effective and safe, with improvement in graft and patient outcomes and no increase in antibody formation or graft rejection.

Development of the InCharge Health Mobile App to Improve Adherence to Hydroxyurea in Patients With Sickle Cell Disease: User-Centered Design Approach

Background

Sickle cell disease (SCD) is an inherited blood disorder causing acute complications and chronic progressive end organ damage. SCD is associated with significant morbidity, early mortality, impaired health-related quality of life, and increased acute health care utilization. Hydroxyurea is a US Food and Drug Administration–approved medication that reduces disease complications, acute health care utilization, and costs. However, adherence to hydroxyurea is suboptimal. Mobile health (mHealth) interventions have the potential to improve hydroxyurea adherence, but few examples exist that are specific to the SCD population.

Objective

This study aimed to design a mHealth intervention for individuals with SCD to improve adherence to hydroxyurea, using a user-centered design that was informed by specific barriers to hydroxyurea adherence and utilization in this population.

Methods

This study consisted of 4 phases. In phase 1, individuals with SCD and health care providers participated in an optimization digital workshop. In phase 2, patients completed surveys pertaining to their interest in mHealth use, barriers and facilitators to hydroxyurea use, and health literacy. Phases 3 and 4 involved semistructured interviews and focus groups, respectively, and used the Health Belief Model (HBM) as the framework to investigate drivers of poor hydroxyurea adherence and to inform the development of an app prototype. In addition, in phase 4, we have incorporated the patients’ feedback on the preliminary app prototype and its features.

Results

Barriers to hydroxyurea adherence were consistent with the literature and included forgetfulness and several specific thoughts and emotions associated with hydroxyurea use (eg, fear of side effects, depression, stigma, and hopelessness). In addition, more than half of the participants reported potentially low health literacy. Preferred patient app features included 7 key components, namely (1) medication reminders and tracker, (2) disease education, (3) communication, (4) personalization, (5) motivation, (6) support during pain episodes, and (7) social support. Utilizing a user-centered design approach, data obtained from patients and providers were translated into features within the app, mapping to components of the HBM and the specific drivers of hydroxyurea adherence and matching the literacy level of the population, resulting in the development of a novel mobile app called InCharge Health.

Conclusions

The InCharge Health app is an mHealth intervention developed with substantial input from users and by mapping the HBM as the framework that guided the choice for its components. InCharge Health is a customized product for the SCD population aimed at optimizing medication adherence, with the end goal of improving quality of life and health outcomes among patients with SCD. The efficacy and implementation of the InCharge Health app as an mHealth intervention to promote hydroxyurea adherence will be tested in a future stepped-wedge multicenter trial for adolescents and adults with SCD.

Prevalence and correlates of microalbuminuria in Yemeni children with sickle cell disease

Microalbuminuria (MA) has been recognized as a sensitive marker of early glomerular injury and a predictor of kidney dysfunction in patients with sickle cell disease (SCD). Limited data are available about MA in SCD children in the Arab countries and none from Yemen. The aim of this study is to determine the prevalence and correlates of MA among 101 children aged 1-16 years, with SCD at their steady state. Children were recruited during their routine health-care visits to the pediatric outpatient clinic in Al-Sadaqa general teaching hospital, Aden, Yemen, between September 2014 and February 2015. A random spot urine sample for each child was screened for MA using Micral-Test strips method. Data on clinical history, anthropometry, blood pressure (BP), and laboratory investigations were obtained. The overall prevalence of MA in this sample was 30.7%, with male predominance (80.6%) (P <0.05). The mean age of children with MA was 7.5 ± 3.2 years, and 10% of them were under five years of age. MA was correlated to both hemoglobin and hematocrit levels, which found to have protective effect against MA (Odds ratio = 0.17 and 0.59, respectively, P <0.05). No correlations were found between MA with age, height, weight, body mass index, recurrent clinical events (painful crises, blood transfusions, and hospitalizations), or fetal hemoglobin levels. BP measurements for all individuals were within the normal ranges, but systolic and diastolic BP were significantly higher in those with MA than without. This study demonstrated a high prevalence of MA in Yemeni children with SCD, and affecting young children as early as 2.5 years of age. Screening for MA as one of the early renal injury markers in children with SCD may help in the prevention of permanent loss of renal function and subsequent renal insufficiency in adulthood.

Non-invasive urinary biomarkers of renal function in sickle cell disease: an overview

Sickle cell disease (SCD) is a hereditary condition characterized by homozygosis of the hemoglobin S (HbS) gene. Marked morbimortality is observed due to chronic hemolysis, endothelial injury, and episodes of vaso-occlusion, which leads to multi-organ damage. Renal impairment is common and may have different presentations, such as deficiency in urinary acidification or concentration, glomerulopathies, proteinuria, and hematuria, frequently resulting in end-stage renal disease (ESRD). Novel biomarkers of renal function, such as kidney injury molecule 1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) and monocyte chemoattractant protein 1 (MCP-1) are being studied in order to enable early diagnosis of kidney damage in SCD.

Sickle cell disease nephropathy: an update on risk factors and potential biomarkers in pediatric patients

One of the major chronic complications of sickle cell disease (SCD) is sickle cell nephropathy. The aim of this review is to discuss the pathophysiology, natural history, clinical manifestations, risk factors, biomarkers and therapeutic approaches for sickle cell nephropathy, focusing on studies with pediatric patients. The earliest manifestation of renal disease is an increase in the glomerular filtration rate. A finding that may also be observed in early childhood is microalbuminuria. Nephrin, KIM-1, VGFs, chemokines and renin-angiotensin system molecules have emerged as potential early markers of renal dysfunction in SCD. In regards to a therapeutic approach, renin-angiotensin system inhibitors and angiotensin receptor blockers seem to be effective for the control of albuminuria in adults with SCD, although new studies in children are needed. The precise moment to begin renoprotection in SCD patients who should be treated remains to be determined.

Sickle cell disease: Clinical presentation and management of a global health challenge

Sickle cell disease is an autosomal recessive, multisystem disorder, characterised by chronic haemolytic anaemia, painful episodes of vaso-occlusion, progressive organ failure and a reduced life expectancy. Sickle cell disease is the most common monogenetic disease, with millions affected worldwide. In well-resourced countries, comprehensive care programs have increased life expectancy of sickle cell disease patients, with almost all infants surviving into adulthood. Therapeutic options for sickle cell disease patients are however, still scarce. Predictors of sickle cell disease severity and a better understanding of pathophysiology and (epi)genetic modifiers are warranted and could lead to more precise management and treatment. This review provides an extensive summary of the pathophysiology and management of sickle cell disease and encompasses the characteristics, complications and current and future treatment options of the disease.

Intermittent or uneven daily administration of low-dose hydroxyurea is effective in treating children with sickle cell anemia in Angola

BACKGROUND

Although hydroxyurea is proven effective in treatment of sickle cell anemia (SCA) and is widely prescribed in high-income countries, due to questions about feasibility of treating large numbers of patients in resource-limited health systems, its use is limited in sub-Saharan Africa (SSA), where most children with SCA live. We assessed hematological response and toxicity of hydroxyurea treatment for SCA in Angola.

METHODS

Retrospective study of children with SCA (not selected for clinical severity) treated on a fixed dose of hydroxyurea for at least 6 months. Because only the 500 mg capsule was available, dose was averaged weekly. We evaluated toxicity events and magnitude of hydroxyurea-induced changes in blood counts and compared patients who received a uniform daily dose to those prescribed intermittent or uneven daily doses.

RESULTS

Only 13% of 303 patients received a uniform dose of hydroxyurea daily. Dose ranged from 16.5 to 22.8 mg/kg/day. Hydroxyurea increased HGB and mean cell volume values by 0.5 g/dL (P < 0.0001) and 8 fL (P < 0.0001), while ANC, PLT, and ARC decreased 1.1 × 10⁹ /L (P < 0.0001), 34 × 10⁹ /L (P = < 0.0001), and 19 × 10⁹ /L (P = 0.0008), respectively. There were no differences in magnitude of hydroxyurea-induced changes between patients prescribed intermittent or uneven doses and uniform daily doses, or between those treated in the lower and higher dose quartiles. Hematological toxicity events were mild and reversible.

CONCLUSION

Intermittent or uneven daily dosing of hydroxyurea is as effective as fixed daily doses in treating SCA. This strategy may enable treatment of additional children with SCA in SSA.

Effect of renin-angiotensin-aldosterone system blocking agents on progression of glomerulopathy in sickle cell disease

Although renin-angiotensin-aldosterone system (RAAS) blocking agents decrease albuminuria in short-term studies, there is no evidence confirming their long-term efficacy in sickle cell disease (SCD). In a single-centre, retrospective study, we evaluated the long-term effect of RAAS blocking agents on proteinuria and declining estimated glomerular filtration rates (eGFR). Eighty-six patients on RAAS blocking agents for proteinuria, followed for a median of 2·28 years, were compared with 68 patients with proteinuria followed for 2·24 years who were not receiving such treatment. The log odds of proteinuria decreased over time in patients on RAAS blocking agents (β: -0·23, P = 0·03) and in the non-treatment group (β: -0·54, P < 0·0001), but was not statistically different between both groups (β: 0·31, P = 0·063). The eGFR declined over time in patients on RAAS blocking agents (β: -2·78, P < 0·0001) and in those not on such treatment (β: -4·7, P < 0·0001), and was statistically different between both groups (β: 1·9, P = 0·0002). Baseline eGFR was associated with mortality (Hazard rato: 0·97, P < 0·0001), but RAAS blocking agents had no significant effect on mortality. These data suggest that RAAS blockade may slow the loss of kidney function in SCD.

Sickle Cell Clinical Research and Intervention Program (SCCRIP): A lifespan cohort study for sickle cell disease progression from the pediatric stage into adulthood

BACKGROUND

Previous natural history studies have advanced the understanding of sickle cell disease (SCD), but generally have not included sufficient lifespan data or investigation of the role of genetics in clinical outcomes, and have often occurred before the widespread use of disease-modifying therapies, such as hydroxyurea and chronic erythrocyte transfusions. To further advance knowledge of SCD, St. Jude Children's Research Hospital established the Sickle Cell Clinical Research and Intervention Program (SCCRIP), to conduct research in a clinically evaluated cohort of individuals with SCD across their lifetime.

PROCEDURES

Initiated in 2014, the SCCRIP study prospectively recruits patients diagnosed with SCD and includes retrospective and longitudinal collection of clinical, neurocognitive, geospatial, psychosocial, and health outcomes data. Biological samples are banked for future genomics and proteomics studies. The organizational structure of SCCRIP is based upon organ/system-specific working groups and is opened to the research community for partnerships.

RESULTS

As of August 2017, 1,044 (92.3% of eligible) patients with SCD have enrolled in the study (860 children and 184 adults), with 11,915 person-years of observation. Population demographics included mean age at last visit of 11.3 years (range 0.7-30.1), 49.8% females, 57.7% treated with hydroxyurea, 8.5% treated with monthly transfusions, and 62.9% hemoglobin (Hb) SS or HbSB⁰ -thalassemia, 25.7% HbSC, 8.4% HbsB⁺ -Thalassemia, 1.7% HbS/HPFH, and 1.2% other.

CONCLUSIONS

The SCCRIP cohort will provide a rich resource for the conduct of high impact multidisciplinary research in SCD.

Sickle cell disease: Classification of clinical complications and approaches to preventive and therapeutic management

Sickle cell disease (SCD) is an inherited disorder of hemoglobin structure that has no established cure in adult patients. Cure has been achieved in selected children with sickle cell anemia (SCA) using allogeneic bone marrow transplantation or cord blood transplantation. SCD is essentially a triumvirate of (1) pain syndromes, (2) anemia and its sequelae and (3) organ failure, including infection. Pain, however, is the hallmark of SCD and dominates its clinical picture throughout the life of the patients. The prevalence of these complications varies with age from infancy through adult life. However, pain, infections and anemia requiring blood transfusion occur throughout the life span of affected patients. The overall medical care of patients with SCD in developed countries has improved such that their life expectancy has almost doubled since 1951. Currently, there are at least five major approaches for the general management of SCD and its complications. These include (i) symptomatic management, (ii) supportive management, (iii) preventive management, (iv) abortive management, and (v) curative therapy.

Prevalence of Microalbuminuria in Adult Patients with Sickle Cell Disease in Eastern Saudi Arabia

Background

Proteinuria is a common feature of sickle cell nephropathy (SCN) that can progress to renal insufficiency and end stage renal disease. Microalbuminuria (MA) is the earliest manifestation of SCN and precedes the development of overt proteinuria. In addition to the renal consequences, MA is linked to cardiovascular complications. Periodic screening and early detection of MA allow early intervention that may reduce the risk of progression to advanced renal failure and cardiovascular diseases.

Objective

The aim of this study was to investigate the prevalence of MA in patients with SCD in the eastern region of Saudi Arabia.

Methods

A prospective cross-sectional observational study was conducted at Johns Hopkins Aramco Healthcare (JHAH). Urine samples of SCD patients 18 years old and older were tested for the presence of MA using urinary albumin over creatinine ratio (ACR). Correlation was tested with multiple variables including age, gender, body mass index (BMI), hemoglobin level, blood pressure, blood transfusion history, pain episodes, and use of hydroxyurea.

Results

Urine samples were tested on 72 patients. The mean age of the study cohort was 35 ± 16.9 years. Microalbuminuria was detected in 18 patients (25%). No correlation was found with any of the tested variables.

Conclusion

Microalbuminuria is a common finding in patients with SCD in eastern Saudi Arabia. Patients with SCD should be screened for MA, and those with positive tests should probably be treated with antiproteinuric agents that may slow the progression to advanced stages of renal failure and decrease the risk of cardiovascular diseases.

Beliefs about hydroxyurea in youth with sickle cell disease

BACKGROUND

Hydroxyurea reduces complications and improves health-related quality of life (HRQOL) in sickle cell disease (SCD) patients, however adherence remains suboptimal. Understanding patients' views of hydroxyurea is critical to optimize adherence, particularly in adolescents and young adults (AYA). Study objectives were to assess beliefs about hydroxyurea using the Beliefs about Medicines Questionnaire (BMQ), and to examine the relationship of patients' beliefs to their hydroxyurea adherence and HRQOL.

METHODS

Thirty-four AYA with SCD participated in a cross-sectional study January-December 2015. Study assessments included BMQ to examine beliefs about hydroxyurea; Visual Analogue Scale (VAS) to assess hydroxyurea adherence; and Patient Reported Outcomes Measurement Information System (PROMIS®) to evaluate HRQOL.

RESULTS

Participants (41% female, 91% Black) had median age of 13.5 (IQR 12-18) years. Participants' concerns about overuse of medications correlated with concerns about hydroxyurea (r_s = 0.36, p = 0.04) and overall harm of medications (r_s = 0.5, p = 0.003). Participants' age positively correlated with the necessity of hydroxyurea (r_s = 0.45, p = 0.007). Participants' concerns about hydroxyurea and overuse of medications positively correlated with anxiety (r_s = 0.41, p = 0.02; r_s = 0.44, p = 0.01) and depression (r_s = 0.37, p = 0.04; r_s = 0.54, p = 0.001), but inversely correlated with peer relationships (r_s = -0.45, p = 0.03; r_s = -0.44, p = 0.03), respectively, suggesting better HRQOL with concerns. Fifty percent of participants reported low hydroxyurea adherence (VAS < 80%), which was more seen in patients with higher concerns about hydroxyurea (p = 0.02).

CONCLUSIONS

Beliefs about hydroxyurea correlated with HRQOL scores and adherence levels. Addressing patients' concern about hydroxyurea and medications overall as well as routine assessment of adherence and beliefs could help to overcome adherence barriers.

Sickle cell nephropathy: an update on pathophysiology, diagnosis, and treatment

Sickle cell nephropathy is a major complication of sickle cell disease. It manifests in different forms, including glomerulopathy, proteinuria, hematuria, and tubular defects, and frequently results in end-stage renal disease (ESRD). Different pathophysiologic mechanisms have been proposed to explain the development of nephropathy in SCD, where hemolysis and vascular occlusion are the main contributors in the manifestations of this disease. Markers of renal injury, such as proteinuria and tubular dysfunction, have been associated with outcomes among patients with sickle cell nephropathy and provide means for early detection of nephropathy and screening prior to progression to renal failure. In small-sized clinical trials, hydroxyurea has demonstrated to be effective in slowing the progression to ESRD. Dialysis and renal transplantation represent the last resort for patients with sickle cell nephropathy. Nevertheless, despite the availability of diagnostic and therapeutic strategies, sickle cell nephropathy remains a challenging and under-recognized complication for patients with sickle cell disease.

[Screening for nephropathy in major sickle cell syndromes in patients monitored at the National Reference Center for Sickle Cell Disease in Niamey, Niger]

BACKGROUND

Sickle cell anemia is the most common hereditary hemopathy in the world. It is a disease that attacks all the systems of the organism. The kidneys are among the most sensitive organs of this disease. The main objective of this study is to detect sickle cell nephropathy in patients followed at the National Reference Center for Sickle Cell Disease in Niamey.

METHODS

It is a prospective study carried out over a period of one year (January to December 2016). It included patients aged at least two years who had not had a vaso-occlusive crisis (VOC) for 2 months and not transfused for at least 3 months. A questionnaire was sent to each patient to collect demographic, clinical and biological information. Each patient provided a fresh blood and urine sample to assess biological parameters. We used Schwartz's formula in children and CKD-EPI in adults to assess glomerular filtration rate. The Pearson correlation coefficient (r) was used to assess the relationship between the different parameters under study. The threshold for statistical significance was set at 0.05.

RESULTS

Two hundred and eighty participants were included in the study. Adolescents (≤17years) were 226 (80.71%) and adults were 54 (19.29%). The mean age of the patients was 11.94±4.70years. It was lower in SS subjects and higher in SC. The SS form accounted for 87.5% of the three sickle cell disease phenotypes encountered. The age group 6-15years was the most predominant (42.86%). The mean baseline hemoglobin in the sample was 7.59±1.15g/dL ; (6.8 ±0.9d/dL) in SS patients and higher (10.5±2.1g/dL) in SC patients. The average glomerular filtration rate was 201.04mL/min/1.73m². Glomerular hyperfiltration was found in 90% of the sample, it was lower (77.6%) in Sβ thalassemia patients (P=0.000). In young subjects hyperfiltration was present in 84.95% against it was observed in only 29.63% of adults. Proteinuria was positive in 20% of patients. Positive proteinuria was found in 6.20% pediatric cases. The SC form was the most affected and in 74.6% of the patients it was positive at 1+. Chronic kidney disease (CKD) was found in 10% of the participants, of whom 75% were of the SS phenotype. Sβ thalassemia subjects had no CKD. The male sex was predominant in subjects with CKD (P=0.000). Patients over 15 years of age accounted for more than 95% of patients in both forms of the disease (P=0.0001).

CONCLUSION

The SS form of the disease, recurrent vaso-occlusive crisis, male sex and advanced age were the main precipitating factors in the development of renal function disorders.

Early Markers of Sickle Nephropathy in Children With Sickle Cell Anemia Are Associated With Red Cell Cation Transport Activity

The early stages of sickle cell nephropathy (SCN) manifest in children with sickle cell anemia (SCA) as hyperfiltration and proteinuria. The physiological conditions of the renovascular system are among the most conducive to hemoglobin S polymerization in the body and will magnify small changes in red cell volume thus crucially modulating intracellular concentrations of hemoglobin S. This large cross-sectional study of children with sickle cell anemia measured glomerular filtration rates and microalbuminuria to report prevalence, clinical correlates and uniquely, association with key red cell cation transport mechanisms. One hundred and twelve patients (mean age 10.7 ± 4.1) were recruited. The prevalence of hyperfiltration and microalbuminuria was 98% and 15.1%, respectively. Glomerular filtration rates did not vary with age, but proteinuria became more prevalent with increasing age. Both features associated with markers of hemolysis, while elevated hemoglobin F was protective, but no association was seen with systolic or diastolic blood pressure. In multivariate analysis, both Gardos channel (β = 0.476, P < 0.001) and KCl co-transporter (KCC; β = -0.216, P = 0.009) activity, alongside age (β = 0.237, P = 0.004), remained independently predictive for microalbuminuria. Increased activity of Gardos channel and P_sickle positively associated with microalbuminuria, while increased KCC activity associated with a reduction in microalbuminuria. This study demonstrates a direct link between the abnormally active red cell cation transport systems in sickle cell disease and sickle organopathy. Small variations in the activity of these transport mechanisms predict for SCN and measurement of them may help identify those at risk, while pharmaceutical manipulation of these excessively active systems may ameliorate their risk.

A clinically meaningful fetal hemoglobin threshold for children with sickle cell anemia during hydroxyurea therapy

Hydroxyurea has proven clinical benefits and is recommended to be offered to all children with sickle cell anemia (SCA), but the optimal dosing regimen remains controversial. Induction of red blood cell fetal hemoglobin (HbF) by hydroxyurea appears to be dose-dependent. However, it is unknown whether maximizing HbF% improves clinical outcomes. HUSTLE (NCT00305175) is a prospective observational study with a primary goal of describing the long-term clinical effects of hydroxyurea escalated to maximal tolerated dose (MTD) in children with SCA. In 230 children, providing 610 patient-years of follow up, the mean attained HbF% at MTD was >20% for up to 4 years of follow-up. When HbF% values were ≤20%, children had twice the odds of hospitalization for any reason (P < .0001), including vaso-occlusive pain (P < .01) and acute chest syndrome (ACS) (P < .01), and more than four times the odds of admission for fever (P < .001). Thirty day readmission rates were not affected by HbF%. Neutropenia (ANC <1000 × 10⁶ /L) was rare (2.3% of all laboratory monitoring), transient, and benign. Therefore, attaining HbF >20% was associated with fewer hospitalizations without significant toxicity. These data support the use of hydroxyurea in children, and suggest that the preferred dosing strategy is one that targets a HbF endpoint >20%.

Changes in urine albumin to creatinine ratio with the initiation of hydroxyurea therapy among children and adolescents with sickle cell disease

BACKGROUND

Renal damage is a progressive complication of sickle cell disease (SCD) that begins in childhood and may progress to renal failure and early mortality in 12% of adults with hemoglobin SS (HbSS) SCD. Early sickle nephropathy is characterized by hyperfiltration and microalbuminuria; therefore, urine albumin to creatinine ratio (ACR) is an effective screening tool for its detection.

PROCEDURE

This study investigated the effect of hydroxyurea (HU) therapy on urine ACR levels among children with SCD. A retrospective review was conducted to identify all patients with HbSS or HbSβ⁰ thalassemia of age 7-18 years who began HU therapy in 2011-2013; a control group of patients not on HU were matched by age and baseline hemoglobin. All urine ACR measurements ≤24 months prior to and ≥24 months after HU initiation were recorded.

RESULTS

There were 63 eligible patients on HU and 13 (25%) with albuminuria prior to HU initiation. Among those with baseline albuminuria, the median ACR was 96 mg/g prior to HU, 39 mg/g at 1 year (P = 0.02), and 25 mg/g at 2 years (P = 0.03). Albuminuria normalized in 37.5% (6/16) after 1 year and 61% (8/13) after 2 years of HU therapy. Among those without albuminuria prior to HU, 13% (6/47) developed albuminuria during HU therapy. Sixteen percent (13/80) of control patients had albuminuria in the beginning of study period, which normalized in 15% (two of 13) of patients at 1-year follow up.

CONCLUSION

Introduction of HU is associated with significant decreases in urine ACR in children with SCD and albuminuria.

Dose Selection Based on Modeling and Simulation for Rivipansel in Pediatric Patients Aged 6 to 11 Years With Sickle Cell Disease

This modeling and simulation exercise aimed to provide dosing recommendations for rivipansel phase III studies in children aged 6–11 years with sickle cell disease (SCD). Pharmacokinetic data from 109 patients aged 12–51 years who received rivipansel (2–40 mg/kg) in previous studies (three phase I and one phase II) were integrated to build a three‐compartmental simulation model. Renal clearance simulations across the age range accounted for renal function development and postulated hyperfiltration in SCD. Simulated demographic distributions for the pediatric SCD population were used to predict concentration‐time profiles from three dosing regimens, which were then compared against efficacious average steady‐state concentrations observed in phase II. A dosing regimen comprising a 40‐mg/kg loading dose followed by a 20‐mg/kg maintenance dose every 12 hours was selected, as it will likely provide an efficacious concentration range. Its validity will be confirmed in the ongoing phase III study.

The spectrum of sickle hemoglobin-related nephropathy: from sickle cell disease to sickle trait

INTRODUCTION

Renal dysfunction is among the most common complication of sickle cell disease (SCD), from hyposthenuria in children to progression to overt chronic kidney disease (CKD) in young adults. Emerging evidence now suggests that sickle hemoglobin-related nephropathy extends to individuals with sickle cell trait (SCT). Areas covered: This review will highlight the pathophysiology, epidemiology, and management recommendations for sickle hemoglobin-related nephropathy in both SCD and SCT. In addition, it will focus on the major demographic and genetic modifiers of renal disease in sickling hemoglobinopathies. Expert commentary: Studies have elucidated the course of renal disease in SCD; however, the scope and age of onset of renal dysfunction in SCT has yet to be determined. In SCD, several modifiers of renal disease - such as α-thalassemia, hemoglobin F, APOL1 and HMOX1 - have been described and provide an opportunity for a precision medicine approach to risk stratify patients who may benefit from early intervention. Extrapolating from this literature may also provide insight into the modifiers of renal disease in SCT. Further studies are needed to determine the optimal treatment for sickle hemoglobin-related nephropathy.

Losartan therapy decreases albuminuria with stable glomerular filtration and permselectivity in sickle cell anemia

Sickle cell nephropathy begins with hyperfiltration and microalbuminuria and may progress to renal failure. The aim of this study was to determine the effects of losartan on glomerular function and albumin excretion in sickle cell anemia (SCA). Individuals with SCA on hydroxyurea with persistent albuminuria were enrolled in a 1-year study of losartan. Glomerular filtration rate (GFR) measured by iohexol clearance, albumin excretion rate (AER), and fractional clearance of dextran were assessed at baseline, short-term (1-2month), and long-term (≥12month) intervals. Twelve subjects (6 microalbuminuria, 6 macroalbuminuria) completed short-term studies; 8 completed long-term studies. Baseline GFR was 112ml/min/1.73m² (71-147ml/min/1.73m²). AER decreased significantly at the short-term (median decrease -134 mcg/min, p=0.0063). GFR was not significantly-different at short-term or long-term intervals. Dextran clearance improved for diameters smaller than albumin (<36Å) but not larger sizes. Losartan therapy for ≥1year in sickle nephropathy results in lower albumin excretion with stable GFR. Filtration of neutral molecules ≥36Å was not changed by losartan, suggesting that the effect of losartan is a mechanism other than alteration of glomerular filtration size-selectivity.

Prevalence and determinants of microalbuminuria in children suffering from sickle cell anemia in steady state

Background

Sickle cell anemia (SCA) is considered a major risk factor for renal complications. The main goal of this study was to determine the frequency of macroalbuminuria and microalbuminuria in Congolese children <18 years of age suffering from Sickle cell anemia and to identify associated factors.

Methods

The cross-sectional study was completed in 150 hemoglobin-SS children (77 boys and 73 girls). Microalbuminuria was defined by a urine albumin:creatinine ratio of 30–299 mg/g.

Results

The mean age of this group was 8.8 ± 4.3 years (range 2–18). Microalbuminuria was found in 27 children (18%). In multivariate logistic regression, only age emerged as a determinant of microalbuminuria odds ratio 1.11 (95% confidence interval 1.00–1.22); P = 0.042].

Conclusions

In our series, only age was a major determinant of the occurrence of microalbuminuria. These results confirm the need for early screening of microalbuminuria in Congolese children suffering from Sickle cell anemia in a context where access to renal and bone marrow transplant is nonexistent.

Interventions for chronic kidney disease in people with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta-globin) genes. SCD can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Kidney disease is a frequent and potentially severe complication in people with SCD.Chronic kidney disease is defined as abnormalities of kidney structure or function, present for more than three months. Sickle cell nephropathy refers to the spectrum of kidney complications in SCD.Glomerular damage is a cause of microalbuminuria and can develop at an early age in children with SCD, and increases in prevalence in adulthood. In people with sickle cell nephropathy, outcomes are poor as a result of the progression to proteinuria and chronic kidney insufficiency. Up to 12% of people who develop sickle cell nephropathy will develop end-stage renal disease.

OBJECTIVES

To assess the effectiveness of any intervention in preventing or reducing kidney complications or chronic kidney disease in people with SCD (including red blood cell transfusions, hydroxyurea and angiotensin-converting enzyme inhibitor (ACEI)), either alone or in combination with each other.

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 05 April 2016. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register: 13 April 2017.

SELECTION CRITERIA

Randomised controlled trials comparing interventions to prevent or reduce kidney complications or chronic kidney disease in people with SCD. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility, extracted data and assessed the risk of bias.

MAIN RESULTS

We included two trials with 215 participants. One trial was published in 2011 and included 193 children aged 9 months to 18 months, and compared treatment with hydroxyurea to placebo. The second trial was published in 1998 and included 22 adults with normal blood pressure and microalbuminuria and compared ACEI to placebo.We rated the quality of evidence as low to very low across different outcomes according to GRADE methodology. This was due to trials having: a high or unclear risk of bias including attrition and detection bias; indirectness (the available evidence was for children aged 9 months to 18 months in one trial and a small and select adult sample size in a second trial); and imprecise outcome effect estimates of significant benefit or harm. Hydroxyurea versus placebo We are very uncertain if hydroxyurea reduces or prevents progression of kidney disease (assessed by change in glomerular filtration rate), or reduces hyperfiltration in children aged 9 to 18 months, mean difference (MD) 0.58 (95% confidence interval (CI) -14.60 to 15.76 (mL/min per 1.73 m²)) (one study; 142 participants; very low-quality evidence).In children aged 9 to 18 months, hydroxyurea may improve the ability to concentrate urine, MD 42.23 (95% CI 12.14 to 72.32 (mOsm/kg)) (one study; 178 participants; low-quality evidence).Hydroxyurea may make little or no difference to SCD-related serious adverse events including: incidence of acute chest syndrome, risk ratio (RR) 0.39 (99% CI 0.13 to 1.16); painful crisis, RR 0.68 (99% CI 0.45 to 1.02); and hospitalisations, RR 0.83 (99% CI 0.68 to 1.01) (one study, 193 participants; low-quality evidence).No deaths occurred in the trial. Quality of life was not reported. ACEI versus placeboWe are very uncertain if ACEI reduces proteinuria in adults with SCD who have normal blood pressure and microalbuminuria, MD -49.00 (95% CI -124.10 to 26.10 (mg per day)) (one study; 22 participants; very low-quality evidence). We are very uncertain if ACEI reduce or prevent kidney disease as measured by creatinine clearance. The authors state that creatinine clearance remained constant over six months in both groups, but no comparative data were provided (very low-quality evidence).All-cause mortality, serious adverse events and quality of life were not reported.

AUTHORS' CONCLUSIONS

In young children aged 9 months to 18 months, we are very uncertain if hydroxyurea improves glomerular filtration rate or reduces hyperfiltration, but it may improve young children's ability to concentrate urine and may make little or no difference on the incidence of acute chest syndrome, painful crises and hospitalisations.We are very uncertain if giving ACEI to adults with normal blood pressure and microalbuminuria has any effect on preventing or reducing kidney complications.This review identified no trials that looked at red cell transfusions nor any combinations of interventions to prevent or reduce kidney complications.Due to lack of evidence this review cannot comment on the management of either children aged over 18 months or adults with any known genotype of SCD.We have identified a lack of adequately-designed and powered studies, and no ongoing trials which address this critical question. Trials of hydroxyurea, ACEI or red blood cell transfusion in older children and adults are urgently needed to determine any effect on prevention or reduction kidney complications in people with SCD.

Sickle cell disease and albuminuria: recent advances in our understanding of sickle cell nephropathy

Albuminuria is considered to be a relevant biomarker for the detection of early glomerular damage in patients with sickle cell disease (SCD). Improvements in our understanding of the pathophysiological processes and molecular mechanisms underlying albuminuria are required, because increasing numbers of patients with SCD are developing chronic kidney disease. The early recognition of sickle cell nephropathy (SCN) and studies of the natural course of this emerging renal disease are therefore crucial, together with identification of the associated clinical and biological risk factors, to make it possible to initiate kidney-protective therapy at early stages of renal impairment. The pathophysiological process underlying SCN remains hypothetical, but chronic haemolysis-related endothelial dysfunction and the relative renal hypoxia triggered by repeated vaso-occlusive crises have been identified as two potential key factors. The optimal preventive and curative management of albuminuria in the context of SCD is yet to be established, but recent studies have suggested that hydroxyurea therapy, the cornerstone of SCD treatment, could play a key role in reducing albuminuria. The place of conventional kidney-protecting measures, such as renin–angiotensin system inhibitors, in the treatment of SCD patients also remains to be determined.

Hydroxycarbamine: from an Old Drug Used in Malignant Hemopathies to a Current Standard in Sickle Cell Disease

While hydroxycarbamide (hydroxyurea, HU) has less and fewer indications in malignant hemopathies, it represents the only widely used drug which modifies sickle cell disease pathogenesis. Clinical experience with HU for patients with sickle cell disease has been accumulated over the past 25 years in Western countries. The review of the literature provides increasing support for safety and efficacy in both children and adults for reducing acute vaso-occlusive events including pain episodes and acute chest syndrome. No increased incidence of leukemia and teratogenicity was demonstrated. HU has become the standard-of-care for sickle cell anemia but remains underused. Barriers to its use should be identified and overcome.