Effects of nonsteroidal antiinflammatory drugs on renal function in sickle cell anemia

Relevance of repeated analyses of albuminuria and glomerular filtration rate in African children with sickle cell anaemia

Glomerular hyperfiltration and albuminuria are frequent kidney abnormalities in children with sickle cell anaemia (SCA). However, little is known about their persistence in African SCA children. This prospective study included 600 steady-state SCA children aged 2-18 years from the Democratic Republic of Congo. Participants were genotyped for apolipoprotein L1 (APOL1) risk variants (RVs) and haem oxygenase-1 (HMOX1) GT-dinucleotide repeats. Kidney abnormalities were defined as albuminuria, hyperfiltration or decreased estimated creatinine-based glomerular filtration rate (eGFRcr). At baseline, 247/600 (41.2%) participants presented with kidney abnormalities: 82/592 (13.8%) with albuminuria, 184/587 (31.3%) with hyperfiltration and 15/587 (2.6%) with decreased eGFRcr. After a median follow-up of 5 months, repeated testing was performed in 180/247 (72.9%) available participants. Persistent hyperfiltration and persistent albuminuria (PA) were present in 29.2% (38/130) and 39.7% (23/58) respectively. eGFR normalized in all participants with a baseline decreased eGFRcr. Haemoglobinuria (p = 0.017) and male gender (p = 0.047) were significantly associated with PA and persistent hyperfiltration respectively. APOL1 RVs (G1G1/G2G2/G1G2) were borderline associated with PA (p = 0.075), while HMOX1 long repeat was not associated with any persistent kidney abnormality. This study reveals that a single screening can overestimate the rate of kidney abnormalities in children with SCA and could lead to overtreatment.

Blockade of the mineralocorticoid receptor improves markers of human endothelial cell dysfunction and hematological indices in a mouse model of sickle cell disease

Increased endothelin-1 (ET-1) levels in patients with sickle cell disease (SCD) and transgenic mouse models of SCD contribute to disordered hematological, vascular, and inflammatory responses. Mineralocorticoid receptor (MR) activation by aldosterone, a critical component of the Renin-Angiotensin-Aldosterone-System, modulates inflammation and vascular reactivity, partly through increased ET-1 expression. However, the role of MR in SCD remains unclear. We hypothesized that MR blockade in transgenic SCD mice would reduce ET-1 levels, improve hematological parameters, and reduce inflammation. Berkeley SCD (BERK) mice, a model of severe SCD, were randomized to either sickle standard chow or chow containing the MR antagonist (MRA), eplerenone (156 mg/Kg), for 14 days. We found that MRA treatment reduced ET-1 plasma levels (p = .04), improved red cell density gradient profile (D50 ; p < .002), and increased mean corpuscular volume in both erythrocytes (p < .02) and reticulocytes (p < .024). MRA treatment also reduced the activity of the erythroid intermediate-conductance Ca2+ -activated K+ channel - KCa 3.1 (Gardos channel, KCNN4), reduced cardiac levels of mRNAs encoding ET-1, Tumor Necrosis Factor Receptor-1, and protein disulfide isomerase (PDI) (p < .01), and decreased plasma PDI and myeloperoxidase activity. Aldosterone (10-8  M for 24 h in vitro) also increased PDI mRNA levels (p < .01) and activity (p < .003) in EA.hy926 human endothelial cells, in a manner blocked by pre-incubation with the MRA canrenoic acid (1 μM; p < .001). Our results suggest a novel role for MR activation in SCD that may exacerbate SCD pathophysiology and clinical complications.

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.

Clinical characteristics and risk factors of relative systemic hypertension and hypertension among sickle cell patients in Cameroon

Increased blood pressure (BP) has been associated with higher risk of stroke and mortality in Sickle Cell Disease (SCD). We investigated risk factors associated with Relative Systemic Hypertension (RSH) or systemic hypertension in SCD patients in Cameroon. Using R, Multivariate multinomial logistic regression modeling was used to examine the effects of the demographic, anthropometric, clinical, and laboratory factors to determine risk factors. A total of 815 individuals with SCD, including 380 (46.6%) males were analyzed. At baseline, the median age [interquartile range] was 18.0 [12.0-25.0] years, ranging from 3 to 66 years. Approximately three-quarters of the patients (n = 645; 79.1%) had normal BP, 151 (18.5%) had RSH and 19 (2.3%) had hypertension. Age (P < 0.001) and gender (P = 0.022) were significantly different across the BP categories. Weight (P < 0.001), height (P < 0.001), BMI (P < 0.001), pulse pressure (P = 0.020), history of stroke (P = 0.012), hemoglobin level (P = 0.002), red blood cell count (P = 0.031), creatinine (P < 0.001), and (estimated glomerular filtration rate) eGFR (P = 0.002) was also significantly different across the three BP categories. After adjustment, the significantly associated factors of RSH in the SCD patients were age [OR = 1.03, (95% CI = 1.01-1.06), P < 0.010], male gender [OR = 1.54, (95% CI = 1.04-2.27), P = 0.029], BMI [OR = 1.10, (95% CI = 1.04-1.17), P = 0.001]. After adjustment, the independent variables significantly associated factors of Hypertension in the SCD patients were age [OR = 1.05, (95% CI = 1.01-1.10), P = 0.034], male gender [OR = 3.31, (95% CI = 1.04-10.52), P = 0.042], BMI [OR = 1.14, (95% CI = 1.01-1.29), P = 0.027]. Creatinine was significantly associated with RSH [OR =1.31 (1.05-1.63), P = 0.016]. SCD patients with RSH or hypertension maybe at increased risk of renal dysfunction. We found relatively high prevalence of RSH and hypertension (20.8%) in SCD patients in Cameroon. Tailored Interventions that consider major risk factors (age, gender, and BMI) may lower BP pressure and prevent severe complications.

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: a review for the internist

Sickle cell disease (SCD) is the most important hemoglobinopathy worldwide in terms of frequency and social impact, recently recognized as a global public health problem by the World Health Organization. It is a monogenic but multisystem disorder with high morbidity and mortality. Vaso-occlusion, hemolytic anemia and vasculopathy are the hallmarks of SCD pathophysiology. This review focuses both on "time-dependent" acute clinical manifestations of SCD and chronic complications commonly described in adults with SCD. The review covers a broad spectrum of topics concerning current management of SCD targeted at the internists and emergency specialists who are increasingly involved in the care of acute and chronic complications of SCD patients.

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.

Hyperfiltration during early childhood precedes albuminuria in pediatric sickle cell nephropathy

BACKGROUND

In patients with diabetes mellitus, hyperfiltration precedes the development of albuminuria. Pediatric sickle cell anemia (SCA) patients have a high prevalence of hyperfiltration and albuminuria during early childhood and adolescence. We tested the hypothesis that hyperfiltration precedes the development of albuminuria in a longitudinal pediatric SCA cohort.

METHODS

We identified 91 participants with HbSS or SB0 thalassemia 5-21 years of age enrolled in a longitudinal sickle cell nephropathy cohort study who had a cystatin C measured during early childhood (4-10 years of age). Early hyperfiltration was defined as a mean eGFR >180 mL/min/1.73m² using cystatin C obtained from 4 to 10 years of age. Persistent albuminuria was defined as an albumin to creatinine ratio > 30 mg/g on two of three untimed urine specimens. Time to event analysis estimated survival curves for participants with and without hyperfiltration using Kaplan-Meier curves and used logrank test for categorical variables to assess the association with time to development of the first episode persistent albuminuria.

RESULTS

Persistent albuminuria occurred more often and at an earlier age in participants with early hyperfiltration compared to those without early hyperfiltration (log-rank, P = .004). Participants who developed albuminuria have a significant increase in their eGFR during childhood (P = .003) as compared to participants who have not yet progressed to albuminuria (P = .26). For every 1 g/dL increase in hemoglobin, the hazard ratio for developing persistent proteinuria decreased by 0.56 (95% CI: 0.3, 1.06, P = .07).

CONCLUSION

Hyperfiltration precedes the development of persistent proteinuria in pediatric SCA patients. Intervention strategies should target lowering eGFR during early childhood.

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.

Standard measures for sickle cell disease research: the PhenX Toolkit sickle cell disease collections

Standard measures and common data elements for sickle cell disease (SCD) will improve the data quality and comparability necessary for cross-study analyses and the development of guidelines that support effective treatments and interventions. In 2014, the National Institutes of Health, National Heart, Lung, and Blood Institute (NHLBI) funded an Administrative Supplement to the PhenX Toolkit (consensus measures for Phenotypes and eXposures; https://www.phenxtoolkit.org/) to identify common measures to promote data comparability across SCD research. An 11-member Sickle Cell Disease Research and Scientific Panel provided guidance to the project, establishing a core collection of SCD-related measures and defining the scope of 2 specialty collections: (1) cardiovascular, pulmonary, and renal complications, and (2) neurology, quality-of-life, and health services. For each specialty collection, a working group of SCD experts selected high-priority measures using a consensus process that included scientific community input. The SCD measures were released into the Toolkit in August 2015. The 25 measures included in the core collection are recommended for use by all NHLBI-funded investigators performing human-subject SCD research. The 10 neurology, quality-of-life, and health services measures and 14 cardiovascular, pulmonary, and renal measures are recommended for use within these specialized research areas. For SCD and other researchers, PhenX measures will promote collaborations with clinicians and patients, facilitate cross-study analysis, accelerate translational research, and lead to greater understanding of SCD phenotypes and epigenetics. For clinicians, using PhenX measures will help elucidate the etiology, progression, and treatment of SCD, leading to improved patient care and quality of life.

Prostacyclin, thromboxane and glomerular filtration rate are abnormal in sickle cell pregnancy

Background

Pregnancy increases the risk of morbidity and mortality in sickle cell disease. We previously showed pregnant women with sickle cell disease to have a relatively low plasma renin concentration in late pregnancy, associated with a lack of the expected plasma volume expansion. We hypothesized this to be due to increased systemic vascular resistance through an imbalance between the vasodilator prostacyclin and vasoconstrictor thromboxane, associated with decreased glomerular filtration rate (GFR).

Objective

To compare estimated prostacyclin, thromboxane and GFR in non-pregnant and pregnant women with hemoglobin SS (HbSS) and AA (HbAA).

Study design

Four groups of 20 normotensive, nulliparous women were studied in Lagos, Nigeria: pregnant HbSS or HbAA women at 36–40 weeks gestation; non-pregnant HbSS and HbAA controls. We measured stable metabolites of prostacyclin and thromboxane A₂ by enzyme-linked immunosorbent assay; GFR using the Cockcroft-Gault equation. Data analysis was by independent (Student’s) t-test or Mann-Whitney U test for comparisons between any two groups of continuous variables, univariate ANOVA for multiple groups and Pearson’s correlation coefficient for degree of association between variables.

Results

HbSS women had lower serum 6-keto-PGF1α concentrations than HbAA, whether pregnant or non-pregnant (P<0.001; P<0.004 respectively). Conversely, pregnant HbSS women had higher serum TxB2 (P<0.001); non-pregnant HbSS women had non-significantly higher TxB2 concentrations. The 6-keto-PGF1α:TxB2 ratio was markedly increased (pro-vasodilatory) in HbAA pregnancy (P<0.001) but reduced in HbSS pregnancy (P = 0.037). GFRs (mL/min) were higher in non-pregnant HbSS than HbAA (P<0.008) but only marginally raised in HbSS women in late pregnancy (P = 0.019) while markedly raised in HbAA pregnancy (P<0.001).

Conclusion

The lower ratio of prostacyclin-thromboxane metabolites in HbSS pregnancy may indicate endothelial damage and an increased tendency to vasoconstriction and clotting. If confirmed by subsequent longitudinal studies, interventions to increase prostacyclin and reduce thromboxane, such as low dose aspirin, may be potentially useful in their management.

Acute kidney injury in children with sickle cell disease-compounding a chronic problem

In an article recently published in Pediatric Nephrology, Baddam and colleagues discuss the relatively underreported clinical problem of repeated episodes of acute kidney injury (AKI) in children with sickle cell disease (SCD). Their report is a cautionary note about the importance of repeated kidney injury on the background of underlying chronic kidney injury and its potential implications on long-term kidney outcome. In children and adults with SCD, this includes the effects of repeated vaso-occlusive crises and the management of these painful episodes with non-steroidal anti-inflammatory drugs. Here we review the scope of kidney involvement in SCD in children and discuss the potential short- and long-term consequences of AKI in children with SCD.

Use of anti-inflammatory analgesics in sickle-cell disease

WHAT IS KNOWN AND OBJECTIVE

Non-steroidal anti-inflammatory drugs (NSAIDs) have been commonly used to treat pain in sickle-cell disease (SCD), but NSAID use is associated with renal, gastrointestinal and cardiovascular toxicities. Our objective was to evaluate the use of aspirin and non-aspirin NSAIDs in SCD.

COMMENT

Despite analgesic and anti-inflammatory benefits in SCD, non-aspirin NSAIDs are associated with renal, cardiovascular and gastrointestinal toxicities in this patient population. Aspirin may have less renal and cardiovascular toxicities. The different side effect profile of NSAIDs is related to the COX-1/COX-2 selectivity at their therapeutic doses. Individual risk factors and genetic biomarkers should be considered when selecting appropriate NSAIDs and their dose.

WHAT IS NEW AND CONCLUSION

NSAIDs have the potential to be an important component of pain regimens in SCD, but the use of NSAIDs should be individualized based on potential side effects and patient risk factors and the lowest effective dose should be prescribed with proper monitoring in patients with SCD.

Elevated tricuspid regurgitant jet velocity, reduced forced expiratory volume in 1 second, and mortality in adults with sickle cell disease

Cardiopulmonary disease is the leading cause of mortality in adults with sickle cell disease (SCD). Elevated tricuspid regurgitant jet velocity (TRJV) and reduced forced expiratory volume in 1 second (FEV₁ ) %predicted are associated with early mortality in SCD; however their relationship and combined effect on survival is unknown. We investigated the relationship between TRJV and FEV₁ %predicted, and their combined effect on mortality, in a retrospective cohort of 189 adults with SCD who underwent both pulmonary function testing and echocardiography. Nineteen (9.9%) of 189 patients died over a median follow-up of 1.4 years; cardiopulmonary disease was the major cause of death in 52.6%. FEV₁ %predicted was negatively associated with TRJV (Spearman rho, -0.34, P < 0.001). Individuals with FEV₁ %predicted ≤70% were more likely to have an elevated TRJV ≥2.5 m/second, compared to those with FEV₁ %predicted >70% [45.8% versus 17.1%; odds ratio (OR) 4.1 (95% Confidence interval ([CI] 2.1-8.0); P = 0.001]. In a multivariable cox regression model, the combination of TRJV ≥2.5 m/second and FEV₁ %predicted ≤70% predicted earlier mortality [hazard ratio (HR) 4.97 (95% CI 1.30-18.91; P = 0.019)] after adjusting for age, sex, and nephropathy. Both FEV₁ %predicted ≤70% and TRJV ≥2.5 m/second were independently associated with nephropathy [OR 4.48 (95% CI 1.51-13.31); P = 0.004] and [OR 3.27 (95% CI 1.19-9.00); P = 0.017], respectively. In conclusion, pulmonary and cardiac impairment are associated with, and contribute to mortality in SCD. Therapies aimed at improving reduced FEV₁ %predicted and elevated TRJV could improve survival in patients with SCD. Am. J. Hematol. 92:125-130, 2017. © 2016 Wiley Periodicals, Inc.

[Kidney and hemoglobinopathy]

Sickle-cell disease (SCD), one of the most common severe monogenic disorders into the world, is associated with an increased frequency of chronic kidney disease. SCD is caused by a point mutation in the gene encoding β globin gene which leads to the formation of hemoglobin S that polymerises after deoxygenation. HbS polymerisation is associated with erythrocyte rigidity and vaso-occlusive episodes that play a central role into SCD pathogenesis. The spectrum of renal diseases during SCD is broad and includes various renal manifestations which become more apparent with increasing age. Underlying pathophysiological processes involved in sickle cell nephropathy are multifactorial but endothelial dysfunction related to chronic hemolysis is a key factor contributing to renal involvement. Our review focuses on the pathogenesis and on the spectrum of renal manifestations occurring in SCD patients.

Changes in Urine Microalbumin-to-Creatinine Ratio in Children with Sickle Cell Disease over Time

BACKGROUND

Approximately 20% of children with sickle cell disease (SCD) have microalbuminuria (MA). Very little is known about the progression of MA in children and young adults with SCD.

METHODS

In this study, we analyzed 5-year EMR data of 373 children [with ≥2 microalbumin-to-creatinine (MA/Cr) ratio measurements] followed at the Medical University of South Carolina to determine the rate, direction, magnitude, and predictors of MA/Cr change over time.

RESULTS

Age range was 1-22 years; mean 10.2 ± 5.2 years, 49.5% were males. Median follow-up duration was 3.12 ± 1.16 years. At baseline, 328 children had normal (<20 mg/L) MA level. Forty-five (12.1%) of children had MA (≥20 mg/L), of which 91% were ≥8 years and 21 (47%) continued to have MA at the end of the study period. On the other hand, during the study period, 24 new patients developed MA and 24 normalized their MA to levels <20 mg/L. In multivariate logistic regression model, age and bilirubin levels were predictive of MA/Cr increase in patients who received at least one blood transfusion during the study period. Baseline MA level was not predictive of the change in MA/Cr.

CONCLUSION

In children and young adults, microalbuminuria is considered a marker of early renal injury. Over time, MA/Cr levels may increase or decrease. Further studies are needed to confirm our findings, assess the reliability of MA as marker of long-term renal injury, and identify high risk patients with SCD likely to have worsening of MA over time.

Novel marker for the detection of sickle cell nephropathy: soluble FMS-like tyrosine kinase-1 (sFLT-1)

BACKGROUND

Given the burden and poor outcome of end-stage renal disease in sickle cell disease (SCD), early markers of sickle cell nephropathy (SN) are desirable. Disordered angiogenesis underlies many complications of SCD. We aimed to determine the relationship between serum FMS-like tyrosine kinase-1 (sFLT-1) and other biomarkers of renal damage for the early diagnosis of SN.

METHODS

Forty-seven SCD patients and 49 healthy controls were enrolled. Microalbuminuria was determined in patient urine samples. Blood samples were tested for sFLT-1, serum creatinine, and various hemolysis and inflammation markers. Peripheral blood monocyte expression of sFLT-1 was measured using real-time polymerase chain reaction (PCR).

RESULTS

The serum level of sFLT-1 (pg/ml) in SCD patients was higher than controls (median/range/IQR = 142/ 60-1300/61 pg/ml vs. 125/ 110-187/52 pg/ml, respectively) (p = 0.006). Median (range) of sFLT-1 level was higher in SCD patients with microalbuminuria compared to SCD patients with normoalbuminuria, 185 (140-1300) vs. 125 (60-189) mg/g, respectively) (p = 0.004). There was a significant positive correlation between serum sFLT-1 and microalbuminuria, lactate dehydrogenase (LDH), and indirect bilirubin (r = 0.59, 0.39, 0.30, and p = <0.001, 0.007, 0.041, respectively). sFLT-1 sensitivity in early detection of renal affection in SCD was 93.6%, while specificity was 68.6%. Finally, peripheral blood monocytes (PBM) sFLT-1 expression was significantly higher in SCD patients compared to controls (p = 0.05).

CONCLUSIONS

sFLT-1 may contribute to pathogenesis of albuminuria in SCD patients and constitute a novel renal biomarker of SN.

Arterial Stiffness and Peripheral and Central Blood Pressure in Patients With Sickle Cell Disease

Blood pressure (BP) in patients with sickle cell disease (SCD) has been reported to be lower than in persons in the general population. Data on arterial stiffness, which is an important risk factor for the progression of BP, are inconclusive for this patient population. Forty-five adult patients with SCD and 40 controls matched for sex, age, and body mass index were studied. Brachial systolic BP (SBP) and diastolic BP (DBP) were significantly lower in the patient group (SBP 115.1±13.8 mm Hg vs 121.9±11.3 mm Hg and DBP 68.5±8.0 mm Hg vs 80.6±9.1 mm Hg, P<.05, respectively). Augmentation index (AIx), however, was significantly higher in SCD patients compared with healthy controls (24.9±9.6 for patients vs 12.4±10.8 for controls, P<.001), while carotid femoral pulse wave velocity was comparable between the two groups. The study shows that mechanisms other than arterial elasticity are involved in the low BP phenotype of patients with SCD.

The glomerulopathy of sickle cell disease

Sickle cell disease (SCD) produces many structural and functional abnormalities in the kidney, including glomerular abnormalities. Albuminuria is the most common manifestation of glomerular damage, with a prevalence between 26 and 68% in adult patients. The pathophysiology of albuminuria in SCD is likely multifactorial, with contributions from hyperfiltration, glomerular hypertension, ischemia-reperfusion injury, oxidative stress, decreased nitric oxide (NO) bioavailability, and endothelial dysfunction. Although its natural history in SCD remains inadequately defined, albuminuria is associated with increased echocardiography-derived tricuspid regurgitant jet velocity, systemic blood pressure, and hypertension, as well as history of stroke, suggesting a shared vasculopathic pathophysiology. While most patients with albuminuria are treated with angiotensin converting enzyme inhibitors/angiotensin receptor blockers, there are no published long-term data on the efficacy of these agents. With the improved patient survival following kidney transplantation, SCD patients with end-stage renal disease should be considered for this treatment modality. Given the high prevalence of albuminuria and its association with multiple SCD-related clinical complications, additional studies are needed to answer several clinically important questions in a bid to adequately elucidate its pathophysiology, natural history, and treatment.

Deferasirox nephrotoxicity-the knowns and unknowns

In 2005, the oral iron chelator deferasirox was approved by the FDA for clinical use as a first-line therapy for blood-transfusion-related iron overload. Nephrotoxicity is the most serious and frequent adverse effect of deferasirox treatment. This nephrotoxicity can present as an acute or chronic decrease in glomerular filtration rate (GFR). Features of proximal tubular dysfunction might also be present. In clinical trials and observational studies, GFR is decreased in 30-100% of patients treated with deferasirox, depending on dose, method of assessment and population studied. Nephrotoxicity is usually nonprogressive and/or reversible and rapid iron depletion is one of several risk factors. Scarce data are available on the molecular mechanisms of nephrotoxicity and the reasons for the specific proximal tubular sensitivity to the drug. Although deferasirox promotes apoptosis of cultured proximal tubular cells, the trigger has not been well characterized. Observational studies are required to track current trends in deferasirox prescription, assess the epidemiology of deferasirox nephrotoxicity in routine clinical practice, explore the effect on outcomes of various monitoring and dose-adjustment protocols and elucidate the long-term consequences of the different features of nephrotoxicity. Deferasirox nephrotoxicity can be more common in the elderly; thus, specific efforts should be dedicated to investigate the effect of deferasirox use in this group of patients.

Hydroxyurea treatment decreases glomerular hyperfiltration in children with sickle cell anemia

Glomerular hyperfiltration and microalbuminuria/proteinuria are early manifestations of sickle nephropathy. The effects of hydroxyurea therapy on these renal manifestations of sickle cell anemia (SCA) are not well defined. Our objective was to investigate the effects of hydroxyurea on glomerular filtration rate (GFR) measured by (99m)Tc-DTPA clearance, and on microalbuminuria/proteinuria in children with SCA. Hydroxyurea study of long-term effects (HUSTLE) is a prospective study (NCT00305175) with the goal of describing the long-term cellular, molecular, and clinical effects of hydroxyurea therapy in SCA. Glomerular filtration rate, urine microalbumin, and serum cystatin C were measured before initiating hydroxyurea therapy and then repeated after 3 years. Baseline and Year 3 values for HUSTLE subjects were compared using the Wilcoxon Signed Rank test. Associations between continuous variables were evaluated using Spearman correlation coefficient. Twenty-three children with SCA (median age 7.5 years, range, 2.5-14.0 years) received hydroxyurea at maximum tolerated dose (MTD, 24.4 ± 4.5 mg/kg/day, range, 15.3-30.6 mg/kg/day). After 3 years of treatment, GFR measured by (99m)Tc-DTPA decreased significantly from 167 ± 46 mL/min/1.73 m² to 145 ± 27 mL/min/1.73 m² (P = 0.016). This decrease in GFR was significantly associated with increase in fetal hemoglobin (P = 0.042) and decrease in lactate dehydrogenase levels (P = 0.035). Urine microalbumin and cystatin C levels did not change significantly. Hydroxyurea at MTD is associated with a decrease in hyperfiltration in young children with SCA.

Sickle cell disease, vasculopathy, and therapeutics

Sickle cell disease (SCD) is caused by a mutation in both beta globin genes, resulting in chronic hemolysis and multiorgan disease that ultimately leads to premature death. Although hemoglobin S (HbS) polymerization and vaso-occlusion are central to the pathogenesis of SCD, overlapping pathways implicated in SCD-related endothelial dysfunction include hemolysis, defects in nitric oxide metabolism, ischemia-reperfusion injury, oxidative stress, increased cell-to-cell adhesion, and proinflammatory and coagulation mediators. Progression of organ-specific vasculopathy often precedes organ dysfunction and may provide targets for therapeutic intervention. SCD-related vasculopathies include, but are not limited to, moyamoya that often precedes cerebral infarcts or hemorrhage, proliferative retinopathy prior to loss of eyesight, pulmonary vasculopathy associated with pulmonary hypertension, and renal vasculopathy prior to the onset of chronic renal disease. This review evaluates evidence that SCD vasculopathy is a harbinger for organ dysfunction and reviews the potential for targeted antivasculopathy therapies.

Prevalence and correlates of microalbuminuria in children with sickle cell anaemia: experience in a tertiary health facility in enugu, Nigeria

Microalbuminuria is a pre-clinical marker of renal damage in children with sickle cell anaemia and can predict renal failure. Reported prevalence rates increased with age. In Nigeria, burden of disease and prevailing poor health facilities necessitate its screening, determination of prevalence and associated risk factors. It is a cross-sectional as well as descriptive study. Screening microalbuminuria used subjects' early morning urine. Socio-demographic as well as clinical details were ascertained using semi-structured questionnaires and case files. Associations and statistical relationship of prevalence rates and clinical/epidemiological data were ascertained using chi-squared and multivariate analysis (P < 0.05). Two hundred children with sickle cell anaemia (4–17 years) in steady state and 200 age/gender-matched controls were enrolled. Prevalence of microalbuminuria was ,respectively, 18.5% and 2.5% for subjects and controls (P = 0.001). Microalbuminuria was commoner in females (19.8%) than males (17.4%) P = 0.70, increased with age (P = 0.016), significantly associated with haemoglobin level (P = 0.002) and hospitalizations (0.001). Subjects had normal renal function. Hospitalizations and haemoglobin levels showed statistical significance on multivariate analysis. Prevalence of microalbuminuria is 18.5%. Age, haemoglobin concentrations, and higher hospitalizations influenced microalbuminuria among subjects. Screening for microalbuminuria should be incorporated in the case management of subjects with identified risk factors.

Evaluation of renal function in sickle cell disease patients in Brazil

The objective of this study was to investigate renal function in a cohort of 98 patients with sickle cell disease (SCD) followed up at a tertiary hospital in Brazil. Clinical and laboratory characteristics at the time of the most recent medical examination were analyzed. Renal function was evaluated by the estimation of glomerular filtration rate (GFR) by the criteria of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI). We compared patients with normal GFR to patients with decreased GFR (<60 mL·min⁻¹·(1.73 m²)⁻¹) and hyperfiltration (>120 mL·min⁻¹·(1.73 m²)⁻¹). Comparison between patients according to the use of hydroxyurea and comparison of clinical and laboratory parameters according to GFR were also carried out. Average patient age was 33.8 ± 13.3 years (range 19-67 years), and 57 (58.1%) patients were females. The comparison of patients according to GFR showed that patients with decreased GFR (<60 mL·min⁻¹·(1.73 m²)⁻¹) were older, had lower levels of hematocrit, hemoglobin and platelets and higher levels of urea and creatinine. Independent risk factors for decreased GFR were advanced age (OR = 21.6, P < 0.0001) and anemia (OR = 39.6, P < 0.0001). Patients with glomerular hyperfiltration tended to be younger, had higher levels of hematocrit, hemoglobin and platelets and lower levels of urea and creatinine, with less frequent urinary abnormalities. Hydroxyurea, at the dosage of 500-1000 mg/day, was being administered to 28.5% of the patients, and there was no significant difference regarding renal function between the two groups. Further studies are required to establish the best therapeutic approach to renal abnormalities in SCD.

Prevalence, treatment, and outcomes of renal conditions in pediatric sickle cell disease

OBJECTIVES

Vaso-occlusive events in pediatric sickle cell disease (SCD) may cause various renal complications and lead to renal failure. We describe the renal conditions that develop among young patients with SCD and the factors associated with the prevalence of these nephropathies.

MATERIALS AND METHODS

Medicaid medical and pharmacy claims for an 11-year period were used to identify 2194 pediatric patients with SCD (HbSS homozygous). Survival analysis identified the most significant predictors of acute kidney injury and chronic renal failure, using demographics, SCD severity and pain medication, comorbid hypertension, hematuria, and proteinuria as the initial covariates.

RESULTS

Prevalence of renal complications in our cohort was found to be relatively low, predominantly hematuria (6.3%) and proteinuria (3.2%). The multivariable analysis indicated that earlier development of acute kidney injury was significantly associated with older age (adjusted hazard ratio [aHR] 1.16, confidence interval [CI] 1.06-1.27), preexisting hypertension (aHR 3.05, CI 1.09-8.60), and preexisting hematuria (aHR 2.87, CI 1.05-7.93). Earlier development of chronic renal failure was significantly associated with older age (aHR 1.20, CI 1.08-1.32), preexisting hematuria (aHR 4.67, CI 1.57-13.94), and preexisting proteinuria (aHR 8.25, CI 2.12-10.38).

CONCLUSIONS

These prevalence findings are novel in the US SCD pediatric population. The predictors of nephropathies identified in these children confirm clinical expectations. In addition, they suggest not only that pediatric nephrologists should be consulted earlier in the treatment of patients with SCD who are diagnosed as having comorbid hypertension or who develop hematuria or proteinuria during the course of their SCD treatment but also that both hydroxyurea and angiotensin-converting enzyme inhibitor therapies may be better used in these cases.

Sickle cell nephropathy: challenging the conventional wisdom

This review explores the current model of sickle cell nephropathy and the limitations of the model. Renal abnormalities are common complications of sickle cell disease (SCD). Beginning in childhood, patients with SCD develop a urinary concentrating defect resulting in polyuria and a predisposition to nocturnal enuresis and dehydration. The current model of sickle cell nephropathy suggests that destruction of the renal medulla induces production of renal vasodilating substances that feedback to the glomerulus causing hyperfiltration. Hyperfiltration leads to glomerulosclerosis and proteinuria, with eventual reduction in kidney function. The crucial steps of vasodilating substance production and hyperfiltration in children with SCD have not been proven. Treatment of sickle cell nephropathy is aimed at the reduction of proteinuria with angiotensin converting enzyme inhibitors or angiotensin receptor blockers. Hydroxyurea and chronic transfusion therapy may also alter the progression of sickle cell nephropathy in children. Further studies are needed to identify an accurate model and effective treatments for sickle cell nephropathy.

Chronic kidney disease and albuminuria in children with sickle cell disease

BACKGROUND AND OBJECTIVES

Sickle cell nephropathy begins in childhood and may progress to renal failure. Albuminuria is a sensitive marker of glomerular damage that may indicate early chronic kidney disease (CKD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The aims of this study were to determine the cross-sectional prevalence and clinical correlates of albuminuria and CKD among children with sickle cell disease (SCD). Over a 10-year period (1995 to 2005) 410 pediatric SCD patients ages 2 to 21 years were enrolled: 261 with hemoglobin SS (HbSS) or HbSβ(0) thalassemia (HbSβ(0)) and 149 with HbSC or HbSβ(+) thalassemia (HbSβ(+)). The albumin/creatinine ratio (ACR) of spot-urine specimens and serum creatinine were measured; abnormal albuminuria was defined as urinary ACR ≥ 30 mg/g.

RESULTS

The prevalence of abnormal albuminuria was 20.7% (23.0% in HbSS/HbSβ(0), 16.8% in HbSC/HbSβ(+)). Among HbSS/HbSβ(0), abnormal albuminuria was associated with increasing age and lower baseline hemoglobin. GFR, estimated in 189 patients using the updated Schwartz formula, correlated negatively with age (r = -0.27, P = 0.0002). CKD defined according to the Kidney Disease: Improving Global Outcomes study was present in 26.5% (50 of 189) of patients: stage 1 in 27 (14.8%) and stage 2 in 22 (11.6%). In multivariate analysis, age and HbSC/HbSβ(+) genotype were associated with CKD.

CONCLUSIONS

This is the first study to stage CKD in children with SCD and highlights a high prevalence of albuminuria and glomerular injury early in life. Detecting CKD in childhood could allow for earlier intervention and prevention of renal failure in adulthood.

Glomerular hyperfiltration and albuminuria in children with sickle cell anemia

Early manifestations of sickle nephropathy include glomerular hyperfiltration and proteinuria, typically microalbuminuria. Over time, a subset of patients develops histologic changes, decreased glomerular filtration, and ultimately renal failure. This study was designed to determine the rate of glomerular hyperfiltration and prevalence of albuminuria in a cross-sectional analysis of untreated children with sickle cell anemia (SCA), and to identify correlates of both complications. Measured glomerular filtration rate (GFR) by plasma clearance of 99-technetium diethylenetriaminepentaacetate was compared to GFR estimates calculated from published formulas. Eighty-five children (mean age 9.4 ± 4.8 years) were studied; 76% had glomerular hyperfiltration with mean GFR = 154 ± 37 ml/min/1.73 m(2). GFR declined in teenage years and was significantly correlated with increased serum cystatin C levels and higher systolic blood pressure. Measured GFR had only modest correlations with GFR estimates (Pearson correlation coefficients ≤0.5). Albuminuria, usually microalbuminuria, occurred in 15.9% and was associated with higher diastolic blood pressure and lower white blood cell and absolute neutrophil counts. Cystatin C levels inversely reflect GFR changes and are associated with albuminuria; serial monitoring may provide a sensitive and accurate marker of nephropathy in children with SCA.

Abdominal ultrasound with scintigraphic and clinical correlates in infants with sickle cell anemia: baseline data from the BABY HUG trial

OBJECTIVE

The purpose of this study is to perform and evaluate baseline abdominal ultrasound in infants with sickle cell anemia who participated in the BABY HUG multiinstitutional randomized placebo-controlled trial of hydroxyurea therapy and to examine the potential relationships among ultrasound results and clinical, nuclear medicine, and laboratory data.

SUBJECTS AND METHODS

After local institutional review board approval and with informed guardian consent, 116 girls and 87 boys (age range, 7.5-18 months) with sickle cell anemia underwent standardized abdominal sonography at 14 institutions. Imaging was centrally reviewed by one radiologist who assessed and measured the spleen, kidneys, gallbladder, and common bile duct. Baseline physical assessment of spleen size, serum alanine aminotransferase and bilirubin levels, (99m)Tc sulfur colloid liver-spleen scans, and (99m)Tc diethylenetriaminepentaacetic acid clearance glomerular filtration rates (GFRs) were obtained. Analysis of variance and the Student test were performed to compare sonographic findings to published results in healthy children and to clinical and laboratory findings.

RESULTS

The mean (± SD) spleen volume (108 ± 47 mL) was significantly greater than published normal control values (30 ± 14 mL; p < 0.0001). There was no correlation between spleen volume and function assessed by liver-spleen scan. The mean GFR (125 ± 34 mL/min/1.73 m(2)) was elevated compared with control GFRs (92 ± 18 mL/min/1.73 m(2)). Renal volumes (right kidney, 29 ± 8 mL; left kidney, 31 ± 9 mL) were significantly greater than control volumes (right kidney, 27 ± 3 mL; left kidney, 27 ± 3 mL; p < 0.0001) and were positively correlated with GFR (p = 0.0009). Five percent of patients had sonographic biliary abnormalities (sludge, n = 6; dilated common bile duct, n = 2; and cholelithiasis and thickened gallbladder wall, n = 1 each). There was no correlation between biliary sonographic findings and laboratory results.

CONCLUSION

In infants with sickle cell anemia, sonographic spleen volume does not reflect function, but increased renal volume correlates with GFR and is consistent with hyperfiltration. Sonographic biliary abnormalities can occur early in life, while remaining clinically silent.

Sub-optimal serum gentamicin concentrations in sickle cell disease patients utilizing the Hartford protocol

WHAT IS KNOWN AND OBJECTIVES

Several studies have reported that use of the Hartford nomogram in different patients' population was associated with low serum gentamicin concentrations (SGC) at different intervals or midpoints. This study was intended to determine the prevalence and predictors of SGC in patients with sickle cell disease (SCD) as another population representing low SGC while utilizing the Hartford protocol.

METHODS

This retrospective observational study was carried out in a University-teaching hospital in Oman. The study was conducted from January 2005 through May 2008 and included all adult patients with SCD admitted during that time. Four-hundred and seven SGC representing 248 SCD patients were evaluated. The serum gentamicin concentration was considered sub-optimal if it was <2μg/mL (baseline of Hartford nomogram). Analyses were performed using univariate and multivariate statistical techniques.

RESULTS AND DISCUSSION

Eighty-three percent (n=339) of SGC were sub-optimal. Multivariate analysis using logistic regression revealed that sub-optimal SGC were associated with younger patients with higher creatinine clearance. Specifically, patients who were ≤23years old were twice more likely to have sub-optimal SGC compared with those who were >23years of age (95% CI: 1·14-3·45; P=0·015). Patients with creatinine clearance of ≥200mL/min were 5·20 times more likely to have sub-optimal SGC compared with those with creatinine clearance <200mL/min (95% CI: 1·81-14·49; P=0·002). Furthermore, the logistic model also demonstrated that higher serum urea was associated with low SGC, with each one unit increase in serum urea, patients were 17% less likely to have sub-optimal SGC (95% CI: 0·72-0·96; P=0·011). Additionally, patients who were on piperacillin±tazobactam therapy given concurrently with gentamicin were 53% less likely to have sub-optimal SGC (95% CI: 0·28-0·83; P=0·009).

WHAT IS NEW AND CONCLUSION

A majority of patients with SCD had sub-optimal SGC. The pharmacokinetic profile of such patients is apparently too variable to fit the existing Hartford protocol. The Hartford nomogram should be modified to address this issue. Otherwise, clinicians should revert to multiple daily dosing.

Lactate dehydrogenase as a predictor of kidney involvement in patients with sickle cell anemia

A retrospective chart review of 40 patients with sickle cell anemia (SCA) between the ages of 5-19 years who were seen within a 1-year period was performed to determine clinical and laboratory correlates for microalbuminuria and proteinuria. Age, sex, height, body mass index (BMI), serum creatinine [and estimated glomerular filtration rate (eGFR) by Schwartz and MDRD formulas], type of SCA, hemoglobin (Hb) level [total Hb and hemoglobin F percentage (HbF%)], lactate dehydrogenase (LDH) level, reticulocyte count, blood pressure, history of splenectomy, history of hydroxyurea use, and history of transfusions were correlated with microalbuminuria and proteinuria by univariate and multivariate regression analysis. The prevalence of microalbuminuria and proteinuria among these patients was 15 and 5%, respectively. Univariate analyses revealed a significant correlation between LDH level and microalbuminuria (Pearson r=0.47, p=0.04) and between LDH level and proteinuria (Pearson r=0.48, p=0.035). Multivariate analysis revealed a significant correlation between microalbuminuria and LDH level (p = 0.04) when controlled for age, sex, eGFR, Hb level, HbF%, type of SCA, BMI, history of transfusions, and reticulocyte count. In this pediatric SCA population, LDH was found to correlate with the presence of microalbuminuria and proteinuria. Further studies are needed to confirm LDH as an early marker for the risk of kidney involvement among SCA patients.

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

Sickle cell disease (SCD) is associated with a large spectrum of renal abnormalities, one of which, microalbuminuria/proteinuria (MA/P), is a known predictor of end-stage renal disease. We studied 90 children with SCD (57% male; mean age 11.4 +/- 5.2 years) to determine the prevalence and examine clinical correlates of MA/P. The average of two spot urine microalbumin-to-creatinine samples obtained 6 months apart was recorded. Medical records were reviewed for demographic and biochemical data. Medication use, resting office blood pressures (BP), vaso-occlusive pain crises (VOC), and monthly transfusions were recorded. Fourteen children (15.5%) had MA/P. Hemoglobin (Hb) levels were significantly lower in the children with MA than in those without MA/P (8.8 +/- 1.1 vs. 9.8 +/- 1.4 g/dL, respectively) and were significantly correlated with MA (rho = 0.24, p = 0.03). Children with MA were more likely to have abnormal BP (p = 0.058), with 5/14 being hypertensive or pre-hypertensive. In a multivariate logistic regression model of MA, both Hb and BP classification remained in the final model. MA is a simple screening biomarker of early kidney injury in children with SCD. Larger studies to evaluate predictive factors of MA and the relationship to BP are needed.

Urine concentrating ability in infants with sickle cell disease: baseline data from the phase III trial of hydroxyurea (BABY HUG)

BACKGROUND

A urine concentrating defect is quite common in sickle cell anemia, has its onset in early childhood, and may be reversible with transfusion. The Pediatric Hydroxyurea Phase III Clinical Trial (BABY HUG) is a double-blind, placebo-controlled trial to assess efficacy of hydroxyurea in preventing organ damage in young children with sickle cell anemia.

PROCEDURES

Enrolled infants were subjected to parent-supervised fluid deprivation, and urine and serum osmolality were determined.

RESULTS

Of 185 infants age 7.5-17.9 months (mean 13.0 +/- 2.7) and fluid-deprived 7.4 +/- 2.4 hr (range 4-13), 178 had concurrent determinations of urine and serum osmolality. Mean serum osmolality was 286 +/- 6 mOsm/kg H(2)O (range 275-312) and independent of age, height, weight, or duration of fluid deprivation. Urine osmolality (mean 407 +/- 151, range 58-794 mOsm/kg H(2)O) was greater than serum (P < 0.0001) and correlated with duration of fluid deprivation (P = 0.001). Of 142 (77.2%) who concentrated urine, 54 (29.4%) had urine osmolality >500 mOsm/kg H(2)O. Urine osmolality correlated with (99m)Tc-DTPA clearance (P = 0.02) and serum urea nitrogen (P < 0.0001), but not with serum osmolality, gender, age, height, weight, or serum creatinine. Infants able to produce urine with osmolality >500 mOsm/kg H(2)O had higher mean fetal hemoglobin concentrations than did those who could not (P = 0.014).

CONCLUSIONS

Even with often limited fluid deprivation, 77.2% of young infants with sickle cell anemia were able to concentrate urine. Preservation of concentrating ability was associated with higher fetal hemoglobin concentration. Assessment will be repeated after 2 years of hydroxyurea or placebo treatment (ClinicalTrials.gov number, NCT00006400).

Renal function in infants with sickle cell anemia: baseline data from the BABY HUG trial

OBJECTIVES

To examine the feasibility and accuracy of glomerular filtration rate (GFR) measurements in infants with sickle cell anemia (SCA).

STUDY DESIGN

The NHLBI/NICHD-sponsored Phase III randomized double-blinded placebo-controlled trial (BABY HUG) tests the hypothesis that hydroxyurea can prevent chronic organ damage in SCA. GFR elevation is a coprimary endpoint, measured quantitatively by technetium 99m-labeled diethylenetriaminepentaacetic acid (DTPA) plasma clearance and estimated by the Schwartz equation with height and creatinine.

RESULTS

Baseline DTPA GFR measurement was attempted in 191 infants; 176 of 184 completed studies (96%) were interpretable. Average age (mean +/- 1SD) was 13.7 +/- 2.6 months. Average DTPA GFR was 125.2 +/- 34.4 (range 40.2-300.9, normal 91.5 +/- 17.8 mL/min/1.73m(2)), while Schwartz estimates were higher at 184.4 +/- 55.5 mL/min/1.73m(2). DTPA GFR was correlated with Schwartz GFR (r(2) = 0.0658, P = .0012); also with age, weight, height, and kidney volume (all P < .002); but not with hemoglobin, HbF, white blood cell count, reticulocytes, medical events, or splenic function.

CONCLUSIONS

Quantitative GFR measurement is feasible but variable among infants with SCA. Schwartz GFR estimates are not highly correlated with quantitative DTPA GFR values. Baseline GFR measurements suggest that renal dysfunction in SCA, evidenced by glomerular hyperfiltration, begins during infancy.

A pilot study of hydroxyurea to prevent chronic organ damage in young children with sickle cell anemia

BACKGROUND

Hydroxyurea improves laboratory parameters and prevents acute clinical complications of sickle cell anemia (SCA) in children and adults, but its effects on organ function remain incompletely defined.

METHODS

To assess the safety and efficacy of hydroxyurea in young children with SCA and to prospectively assess kidney and brain function, 14 young children (mean age 35 months) received hydroxyurea at a mean maximum tolerated dose (MTD) of 28 mg/kg/day.

RESULTS

After a mean of 25 months, expected laboratory effects included significant increases in hemoglobin, MCV and %HbF along with significant decreases in reticulocytes, absolute neutrophil count, and bilirubin. There was no significant increase in glomerular filtration rate by DTPA clearance or Schwartz estimate. Mean transcranial Doppler (TCD) velocity changes were -25.6 cm/sec (P < 0.01) and -26.8 cm/sec (P < 0.05) in the right and left MCA vessels, respectively. At study exit, no child had conditional or abnormal TCD values, and none developed brain ischemic lesions or vasculopathy progression by MRI/MRA. Growth and neurocognitive scores were preserved and Impact-on-Family scores improved.

CONCLUSIONS

These pilot data indicate hydroxyurea at MTD is well-tolerated by both children and families, and may prevent chronic organ damage in young children with SCA.

Short-term follow-up of patients with sickle cell disease and albuminuria

BACKGROUND

Albuminuria with normal serum creatinine occurs frequently in patients with sickle cell disease (SCD), but the rate of progression to more advanced chronic renal disease is unknown. The purpose of this study was to investigate the rate of progression of children and young adults with SCD and albuminuria over time.

PROCEDURE

Urine albumin/creatinine (A/C) ratios and serum creatinine were obtained serially. Serum cystatin C levels were determined in a subgroup of 20 patients.

RESULTS

Of 38 patients with SCD who had albuminuria (30 with microalbuminuria and 8 with proteinuria), 10.5% had progressive disease during follow-up of 20 +/- 12 months. Progressive disease was observed in 2 of 30 patients with MA because MA worsened to either intermittent proteinuria (1 patient), or persistent proteinuria after 7 months follow-up (1 patient). Two of eight patients with proteinuria worsened to nephrotic-range after 8 and 17 months with elevations of serum creatinine. All eight patients with proteinuria were treated with angiotensin blockade and/or hydroxyurea. Of those, six patients responded to treatment with decreased albuminuria and no changes in serum creatinine. Serum cystatin C level trended to increase before serum creatinine in patients with proteinuria.

CONCLUSIONS

Patients with rapid progression to nephrotic-range proteinuria showed decreased kidney function. Therefore, patients with albuminuria should be monitored closely for progression, and therapy with hydroxyurea and/or angiotensin blockade should be considered for patients who develop proteinuria. Serum cystatin C appears more sensitive than serum creatinine to detect early decrease in kidney function.

Clinical application of deferasirox: practical patient management

Deferasirox (Exjade, ICL670) is a once-daily, oral iron chelation agent that is now widely available for the treatment of transfusional hemosiderosis in adult and pediatric patients aged > or =2 years of age. Clinical evaluation has established the efficacy and safety of this novel agent in patients with a variety of chronic anemias. Deferasirox represents a significant advance in the treatment of iron overload, as the availability of an effective oral therapy has the potential to relieve many patients from the burden of frequent parenteral therapy with the previous reference standard iron chelator, deferoxamine. The most common drug-related adverse events seen in the core registration trials were gastrointestinal disturbances, rash, mild and nonprogressive increases in serum creatinine levels, and elevations in liver enzyme levels. Most events were transient, mild-to-moderate in severity, and easily managed without discontinuation of treatment. As with any new agent, it is important that treating physicians are familiar with the adverse event profile of deferasirox and how the associated effects can be readily managed to ensure optimal use of this important treatment.

Pulmonary hypertension associated with sickle cell disease: clinical and laboratory endpoints and disease outcomes

Screening for pulmonary hypertension (pHTN) has not yet become routine in sickle cell disease (SCD), despite clinical evidence of its high prevalence and associated mortality. Our objectives are to identify clinical conditions and laboratory findings predictive of/or associated with pHTN. One hundred twenty-five adult outpatients with Hb SS, SC, SOArab, Sbeta(0), or Sbeta(+) thalassemia, who underwent echocardiography and/or right heart catheterization due to cardiorespiratory symptoms, were studied. pHTN was identified in 36% (28/77) of SS/Sbeta(0) and in 25% (12/48) of SC/SOArab/Sbeta(+) patients studied. In SS/Sbeta(0) patients, pHTN was associated with low hemoglobin, low GFR, increasing age, no history of treatment with hydroxyurea and a history of leg ulcers, with trends for associations with higher total bilirubin, LDH levels, systolic systemic blood pressure, history of avascular necrosis, seizures, and cerebrovascular events. Twelve (40%) of the SS/Sbeta(0) patients with pHTN had >or= 1+ proteinuria. (P<0.039). The presence of proteinuria correlated with lower GFR and had a high positive predictive value (0.60) for pHTN in subjects with SS/Sbeta(0). The data also provided evidence that pHTN in this population is associated with right heart failure, with echocardiographic evidence of right ventricle enlargement and pericardial effusion. This study confirmed that even relatively mild elevations in pulmonary pressure are associated with high prospective mortality (hazard ratio: 15.9). We concluded that pHTN has a high prevalence in all Hb S related syndromes and is associated with increased mortality in SS/Sbeta(0). Kidney dysfunction, as indicated by proteinuria or decreased GFR, also represents sufficient reason to screen for pHTN.

51Cr-EDTA measurements of the glomerular filtration rate in patients with sickle cell anaemia and minor renal damage

BACKGROUND

Creatinine clearance has been reported to be inaccurate for the estimation of glomerular filtration rate (GFR) in patients with sickle cell anaemia (SCA). Inulin clearance, the reference method for GFR estimation, is impractical for routine use in these patients, and 51Cr-EDTA measurements of the GFR have been rarely reported in this disease.

METHODS

In order to obtain reference 51Cr-EDTA values in this disease, we studied 70 patients (40 females; 13-59 years of age, mean: 31.6 years) with homozygous SCA, normal serum creatinine and urinary albumin excretion < or =200 microg x min(-1). All patients were submitted to single-injection 51Cr-EDTA GFR, urinary albumin and haematocrit measurements. 51Cr-EDTA clearances were calculated in different age groups (<20, 20-29, 30-39, 40-49 and >50 years).

RESULTS

The mean GFR (+/-standard deviation) obtained for the 70 patients was 111.5+/-23.1 ml x min(-1). Analysis of variance for evaluation of the possible interaction effect between 51Cr-EDTA clearance and sex, age, urinary albumin and haematocrit demonstrated patient age as the only factor influencing 51Cr-EDTA clearance (P < 0.001). The Spearman correlation coefficient showed a significant relationship between 51Cr-EDTA clearance and patient age (r = -0.44, P = 0.0001), but not between 51Cr-EDTA and urinary albumin (r = -0.17, P = 0.1546) or haematocrit (r = 0.079, P = 0.5121). The group aged 20-29 years presented the highest 51Cr-EDTA clearance mean value (126.7+/-20.4 ml x min(-1)), with a progressive reduction in the older groups.

CONCLUSION

Young adults with homozygous SCA, normal serum creatinine and micro-albuminuria or normo-albuminuria present supranormal 51Cr-EDTA GFR values. These values rapidly decrease after 30 years of age. We did not find association between urinary albumin and GFR in these patients.

Differential gene expression in the kidney of sickle cell transgenic mice: upregulated genes

The S+S-Antilles transgenic mouse used in this study has renal defects similar to those seen in sickle cell anemia patients: congested glomeruli, medullary fibrosis, renal enlargement, vasoocclusion, and a urine concentrating defect. We used gene expression microarrays to identify genes highly up-regulated in the kidneys of these mice and validated their expression by real-time PCR. Kidney hypoxia, as demonstrated by the presence of deoxyhemoglobin, was detected by blood oxygen dependent magnetic resonance imaging (BOLD-MRI). Some of the up-regulated genes included cytochrome P450 4a14, glutathione-S-transferase alpha-1, mitochondrial hydroxymethylglutaryl CoA synthase, cytokine inducible SH-2 containing protein, retinol dehydrogenase type III, arginase II, glycolate oxidase, Na/K ATPase, renin-1, and alkaline phosphatase 2. An increase in enzyme activity was also demonstrated for one of the up-regulated genes (arginase II). These genes can be integrated into several different pathophysiological processes: a hypoxia cascade, a replacement cascade, or an ameliorating cascade, one or all of which may explain the phenotype of this disease. We conclude that microarray technology is a powerful tool to identify genes involved in renal disease in sickle cell anemia and that the identification of various metabolic pathways may open new avenues for therapeutic interventions.

Microalbuminuria as a predictor of early glomerular injury in children with sickle cell disease

OBJECTIVE

A cross sectional study was carried out to determine the prevalence of microalbuminuria in the pediatric patients with sickle cell disease.

METHODS

The study was carried out on 64 pediatric patients aged less than 14 years with documented HbSS, HbAS and HbS beta thalassemia, Microalbuminuria was estimated using single radial immuno diffusion technique. Majority of the study subjects were of HbSS type. 38.5% had symptoms for > 2 years. 18.8% of the study population had significant microalbuminuria (19.2% of SS type and 18.8% of Hb AS types).

RESULT

Microalbuminuria excretion was significantly more in patients > 9 years of age as compared to young patients (p < 0.05). Mean serum creatinine levels did not show any significant difference in the various study groups.

CONCLUSION

Microalbuminuria estimation is a very important clinical marker of preclinical glomerular damage in patients with sickle cell disease. It estimation would help in the early detection of such patients and prompt initiation of therapy.