Renal function in children suffering from sickle cell disease: challenge of early detection in highly resource-scarce settings

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.

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.

Reduced blood pressure in sickle cell disease is associated with decreased angiotensin converting enzyme (ACE) activity and is not modulated by ACE inhibition

Background

Sickle cell disease (SCD) incurs vaso-occlusive episodes and organ damage, including nephropathy. Despite displaying characteristics of vascular dysfunction, SCD patients tend to present relatively lower systemic blood pressure (BP), via an unknown mechanism. We investigated associations between BP and renin-angiotensin-system (RAS) components in SCD and determined whether an inhibitor of angiotensin converting enzyme (ACE; often used to slow SCD glomerulopathy) further modulates BP and RAS components in a murine model of SCD.

Methods

BP was compared in human subjects and mice with/without SCD. Plasma angiotensin II, ACE and renin were measured by immunoassay. BP was reevaluated after treating mice with enalapril (25 mg/kg, 5x/week) for 5 weeks; plasma and organs were stored for angiotensin II and ACE activity measurement, and quantitative real-time PCR.

Results

Diastolic BP and systolic BP were significantly lower in patients and mice with SCD, respectively, compared to controls. Reduced BP was associated with increased plasma renin and markers of kidney damage (mice) in SCD, as well as significantly decreased plasma ACE concentrations and ACE enzyme activity. As expected, enalapril administration lowered BP, plasma angiotensin II and organ ACE activity in control mice. In contrast, enalapril did not further reduce BP or organ ACE activity in SCD mice; however, plasma angiotensin II and renin levels were found to be significantly higher in enalapril-treated SCD mice than those of treated control mice.

Conclusion

Relative hypotension was confirmed in a murine model of SCD, in association with decreased ACE concentrations in both human and murine disease. Given that ACE inhibition has an accepted role in decreasing BP, further studies should investigate mechanisms by which ACE depletion, via both Ang II-dependent and alternative pathways, could contribute to reduce BP in SCD and understand how ACE inhibition confers Ang II-independent benefits on kidney function in SCD.

Clinical and genetic factors are associated with kidney complications in African children with sickle cell anaemia

Clinical and genetic factors have been reported as influencing the development of sickle cell nephropathy (SCN). However, such data remain limited in the paediatric population. In this cross-sectional study, we enrolled 361 sickle cell disease children from the Democratic Republic of Congo. Participants were genotyped for the beta (β)-globin gene, apolipoprotein L1 (APOL1) risk variants, and haem oxygenase-1 (HMOX1) GT-dinucleotide repeats. As markers of kidney damage, albuminuria, hyperfiltration and decreased estimated glomerular filtration with creatinine (eGFRcr) were measured. An association of independent clinical and genetic factors with these markers of kidney damage were assessed via regression analysis. Genetic sequencing confirmed sickle cell anaemia in 326 participants. Albuminuria, hyperfiltration and decreased eGFRcr were present in 65 (20%), 52 (16%) and 18 (5·5%) patients, respectively. Regression analysis revealed frequent blood transfusions, indirect bilirubin and male gender as clinical predictors of SCN. APOL1 high-risk genotype (G1/G1, G2/G2 and G1/G2) was significantly associated with albuminuria (P = 0·04) and hyperfiltration (P = 0·001). HMOX1 GT-dinucleotide long repeats were significantly associated with lower eGFRcr. The study revealed a high burden of kidney damage among Congolese children and provided evidence of the possible role of APOL1 and HMOX1 in making children more susceptible to kidney complications.

Novel kidney injury biomarkers in a large cohort of children with sickle cell anemia

Aim: The aim of this study was to compare novel kidney injury biomarkers in sickle cell anemia (SCA) children with and without albuminuria or glomerular hyperfiltration. Materials & methods: A total of 358 Brazilian children with SCA were studied. Fifteen kidney injury biomarkers in urine were measured. Albuminuria was defined as urine albumin/creatinine ratio >100 mg/g. Glomerular hyperfiltration was defined as estimated glomerular filtration rate ≥140 ml/min/1.73 m². Results: After adjustment for age, sex and modifying therapies in use, EGF and collagen IV urinary levels were associated with albuminuria. Renin and clusterin levels were associated with hyperfiltration. Conclusion: Levels of novel kidney injury biomarkers were associated with albuminuria and hyperfiltration in Brazilian children with SCA, suggesting concomitant structural and functional abnormalities.

Abnormal Ambulatory Blood Pressure and Early Renal Dysfunction in Sickle Cell Disease

OBJECTIVES

There is sparsity of studies evaluating blood pressure in children with sickle cell disease (SCD), which have shown inconsistent results. Few of the studies have documented lower office blood pressure (BP) in SCD patients, whereas, others have shown presence of masked hypertension and abnormal ambulatory blood BP monitoring (ABPM). Thus, the present study was conducted to examine 24 h ABPM parameters and renal dysfunction in children with SCD and compare them with healthy controls.

METHODS

A cross-sectional study was conducted on 56 children (30 children having SCD and 26 controls). ABPM and evaluation of renal functions including serum creatinine, serum urea, urinary creatinine, urinary protein and specific gravity was performed.

RESULTS

Spot urinary protein to creatinine ratio was found to be higher in patients with SCD (63.3%) as compared to controls (p < 0.001). Proteinuria was observed in 1/4th of the SCD patients less than ten years of age. Masked hypertension was present in 2 (6.6%) patients, ambulatory hypertension in 4 (13.3%), ambulatory pre-hypertension in 1 (3.3%) and abnormal dipping in 60%. A statistically significant correlation of BMI for age Z-score and standard deviation score (SDS/Z) of 24 h systolic BP (r = 0.56, p = 0.002); estimated glomerular filtration rate (eGFR) with 24 h diastolic BP SDS (r = -0.52; p = 0.038) and age with e GFR (r = 0.54; p = 0.025) was found in the present study.

CONCLUSIONS

The present study corroborates that ABPM abnormalities (ambulatory hypertension, non-dipping pattern, ambulatory prehypertension) and early onset proteinuria are significant findings in patients with SCD. This underscores the importance of regular screening for proteinuria and ABPM in routine care, for early detection and prevention of progressive renal damage in SCD.

Assessment of Renal Function Status in Steady-State Sickle Cell Anaemic Children Using Urine Human Neutrophil Gelatinase-Associated Lipocalin and Albumin:Creatinine Ratio

INTRODUCTION

Sickle cell anaemia is characterized by defective haemoglobin synthesis and is associated with both endocrine and metabolic alterations. The effects of this clinical condition on kidney function are multifactorial and often begin early in childhood. This study aims to assess renal function in children with sickle cell anaemia using urine albumin:creatinine ratio (ACR) and urine human neutrophil gelatinase-associated lipocalin (NGAL).

METHODS

This case-control study was conducted on 200 children aged 5-15 years in 2 tertiary hospitals in South West Nigeria: 150 were of haemoglobin S genotype and 50 were of haemoglobin A genotype. Serum urea, creatinine, urine albumin, and NGAL were assayed by known standard methods. eGFR, urine ACR, and urine NGAL/creatinine ratio (urine NCR) were calculated.

RESULTS

The weight, height, BMI, systolic blood pressure, plasma urea, plasma creatinine, and spot urine creatinine of the HbS genotype children were significantly lower compared to that of the HbA genotype children. The eGFR, spot urine albumin, and urine ACR were significantly higher in the HbS group compared to the HbA group. There was no significant difference in the spot urine NGAL and urine NCR between the 2 groups, though both were higher in the HbS group compared to the HbA group.

CONCLUSIONS

Kidney injury probably starts early in childhood in sickle cell individuals as indicated by the higher urine ACR detected in them. We infer that urine NGAL and uNCR are not sensitive markers of kidney disease especially in young sickle cell individuals possibly because of the hyperfiltration present at this age.

Association between renal function parameters, clinical severity score and mortality risk among adult Sudanese sickle anemia patients

BACKGROUND

Sickle Cell Anemia (SCA) is an autosomal recessive haemoglobinopathy with high morbidity and mortality. Global survival of sickle patients is increased due to advances in management; and subsequently, prevalence of chronic complications including renal manifestations also increased. Therefore, early detection and management of these complications is mandatory. This study aimed to investigate the estimated Glomerular Filtration Rate (eGFR), proteinuria and serum uric acid as markers of renal involvement in Sudanese sickle adults and association between these parameters and clinical severity score of sickle cell disease.

METHODS

Cross-sectional hospital-based study included thirty-two adult Sudanese patients diagnosed with SCA and twenty-three as controls. Written informed consent was obtained from each participant. Blood and urine samples were collected. Severity score was calculated using Bios online calculator and eGFR was calculated using Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula without adjustment for ethnicity. Associations between the severity score and renal parameters were tested using unpaired T test and Mann Whitney test for normally and non-normally distributed data and correlations between variables were tested using SPSS version 23.

RESULTS

Protein/Creatinine Ratio (PCR) was significantly higher (p-value < 0.001) in sickle cell anaemia group compared to controls. Hyper-filtration and Hyperuricemia were manifested in 75% and 6.3% of SCA group respectively. There was no association between the severity score and renal manifestations in the SCA group.

CONCLUSIONS

Hyper-filtration and proteinuria were the most prevalent renal manifestations in SCA group. Further studies are recommended to determine the predictors of renal complications and ensure early management of such complications.

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.

Sickle Cell Nephropathy and Associated Factors among Asymptomatic Children with Sickle Cell Anaemia

BACKGROUND

Sickle cell nephropathy (SCN) is a serious complication of sickle cell anaemia (SCA) with asymptomatic onset in childhood and possible progression to chronic kidney disease (CKD). In Southeast Nigeria, few studies have evaluated renal function in paediatric SCA patients for early detection of renal impairment and early intervention to reduce morbidity and mortality. Therefore, this study evaluated the renal function of paediatric SCA patients in a steady state based on glomerular filtration rate and urinalysis findings (proteinuria and haematuria).

METHODS

A cross-sectional study of consecutively recruited sixty haemoglobin SS (HbSS) children in a steady state and sixty age- and sex-matched haemoglobin AA (HbAA) controls aged 2-18 years was done. Renal function of HbSS subjects was evaluated using estimated glomerular filtration rate (eGFR) which was compared with healthy HbAA subjects. The prevalence of significant proteinuria and haematuria, its association with eGFR, and the effect of past sickle cell crisis (in the preceding 24 months) on renal function were also evaluated.

RESULTS

Mean eGFR was significantly higher in HbSS subjects than in the HbAA subjects (p = 0.001) and decreased with age. Significant proteinuria and haematuria were more prevalent in the HbSS group (3.4% and 6.7%, respectively) compared to the HbAA subjects (0% and 0%, respectively) (p = 0.496 and 0.119, respectively). No significant association was observed between eGFR and proteinuria (p = 1.000) or haematuria (p = 1.000). There was a positive correlation between eGFR and frequency of past painful crisis that required hospitalization (r = 0.138, p = 0.295) and between eGFR and frequency of blood transfusion (r = 0.679, p ≤ 0.001).

CONCLUSIONS

Asymptomatic paediatric HbSS (SCA) patients had higher mean eGFR indicating an increased risk of nephropathy. There was no association between eGFR and proteinuria or haematuria. Frequent sickle cell crises especially one requiring transfusion were positively correlated with hyperfiltration.

Association between Endothelial Dysfunction, Biomarkers of Renal Function, and Disease Severity in Sickle Cell Disease

Background

Endothelial dysfunction (ED), as ascertained by brachial artery flow-mediated dilation (FMD), is a known feature of sickle cell disease (SCD), which is present both in crisis and in steady state. The assessment of FMD was introduced to examine the vasodilator function. Our objective was to establish the relationship between ED determined by FMD, biomarkers of renal dysfunction, and biomarkers of disease severity in SCD subjects asymptomatic of renal disease.

Methods

We enrolled 44 patients with homozygous SCD in steady state and 33 age- and sex-matched controls between 2013 and 2014 in a tropical tertiary hospital. Ultrasonographic FMD of the right brachial artery, renal arterial Doppler, complete blood count, creatinine, fetal hemoglobin, soluble P-selectin, and cystatin C (Cys-C) levels were determined. Using the median FMD value of the control group, the SCD subjects were further classified into two groups for comparison.

Results

The median FMD in SCD subjects of 3.44 (IQR, 0.00-7.08) was significantly lower than that of controls, which was 5.35 (IQR, 3.60-6.78; P=0.04). There was negative correlation between FMD and Cys-C levels (r=-0.372; P=0.01) along with renal artery resistivity index (RARI; r=-0.307; P=0.04) in SCD subjects. Additionally, Cys-C level was significantly higher in SCD subjects with FMD<5.35.

Conclusions

Brachial artery FMD was significantly lower in SCD subjects compared with a control group. Cys-C and RARI show a negative correlation with FMD, indicating that renal function is related to ED 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.

Impact of ET-1 and sex in glomerular hyperfiltration in humanized sickle cell mice

Hyperfiltration, highly prevalent early in sickle cell disease (SCD), is in part driven by an increase in ultrafiltration coefficient (K_f). The increase in K_f may be due to enlarged filtration surface area and/or increased glomerular permeability (P_alb). Previous studies have demonstrated that endothelin-1 (ET-1) contributes to P_alb changes in models of diabetes and SCD. Thus, we performed longitudinal studies of renal function to determine the relationship between ET-1 and glomerular size and P_alb that may contribute to hyperfiltration in humanized sickle cell (HbSS) and control (HbAA) mice at 8-32 weeks of age. HbSS mice were characterized by significant increases in plasma and glomerular ET-1 expression in both sexes although this increase was significantly greater in males. HbSS glomeruli of both males and females presented with a progressive and significant increase in glomerular size, volume, and K_f During the onset of hyperfiltration, plasma and glomerular ET-1 expression were associated with a greater increase in glomerular size and K_f in HbSS mice, regardless of sex. The pattern of P_alb augmentation during the hyperfiltration was also associated with an increase in glomerular ET-1 expression, in both male and female HbSS mice. However, the increase in P_alb was significantly greater in males and delayed in time in females. Additionally, selective endothelin A receptor (ET_A) antagonist prevented hyperfiltration in HbSS, regardless of sex. These results suggest that marked sex disparity in glomerular hyperfiltration may be driven, in part, by ET-1-dependent ultra-structural changes in filtration barrier components contributing to glomerular hyperfiltration in HbSS mice.

Prevalence and factors associated with renal dysfunction among children with sickle cell disease attending the sickle cell disease clinic at a tertiary hospital in Northwestern Tanzania

BACKGROUND

Little is known on how the interaction between Sickle Cell Disease (SCD) and renal insults caused by other coexisting conditions in Sub Saharan Africa such as urinary schistosomiasis, malnutrition and HIV affect the prevalence of renal dysfunction in children with SCD.

OBJECTIVES

To determine the prevalence and factors associated with renal dysfunction among children with SCD aged 6 months to 12 years attended at a tertiary hospital in Northwestern Tanzania.

METHODS

A cross sectional hospital-based study with a short follow up component of 3 months for 153 children with SCD was done to document demographics, clinical characteristics and features of renal dysfunction including urine dipstick albuminuria (>20mg/l) and eGFR (<60ml/ml/min/1.73m2). Other potential renal insults such as HIV infection and Schistosomiasis were also evaluated.

RESULTS

At enrollment, 48/153(31.37%) children had renal dysfunction declining to 31(20.3%) at 3 months follow up. Acute chest syndrome (OR 3.04, 95% CI [1.08-8.96], p = 0.044), severe anemia (OR 0.44, 95% CI [0.26-0.76],p = 0.003), urinary schistosomiasis (OR 7.43, 95% CI [2.10-26.32] p<0.002) and acute malnutrition (OR 4.92, 95% CI [1.29-18.84], p = 0.020). were associated with renal dysfunction.

CONCLUSION

Where prevalent, urinary schistosomiasis and acute malnutrition increase the risk for renal dysfunction in children with SCD. We recommend albuminuria routine screening in children with SCD especially those presenting with acute chest syndrome, severe anemia and features of acute malnutrition for early detection of renal dysfunction among children with SCD.

Biochemical effects and safety of Gum arabic (Acacia Senegal) supplementation in patients with sickle cell anemia

Background

Sickle cell anemia (SCA) is a hereditary chronic hemolytic anemia with several clinical consequences. Intravascular sickling of red blood cells leads to multi-organ dysfunction. Moreover, several biochemical abnormalities have been associated with SCA. Gum arabic (GA) is an edible dried gummy exudate obtained from Acacia Senegal tree. GA showed antioxidant and cytoprotective activities and demonstrated protection against hepatic, renal, and cardiac toxicities in experimental rats. We hypothesized that regular intake of GA improves renal and liver functions in patients with SCA.

Methods

Forty-seven patients (5–42 yr) carrying hemoglobin SS were recruited. The patients received 30 g/day GA for 12 weeks. Blood samples were collected before administering GA and then after 4, 8, and 12 weeks. Liver enzymes, total protein, albumin, electrolytes, urea, creatinine, and uric acid were determined in the serum. The study was approved by the Al Neelain University Institutional Review Board and Research Ethics Committee Ministry of Health. The trial was registered at ClinicalTrials.gov (identifier: NCT02467257).

Results

GA significantly decreased direct bilirubin level [statistical significance (P-value)=0.04]. It also significantly decreased serum alanine transaminase level after 4 weeks, which was sustained till the 8th week. GA, however, had no effect on serum aspartate transaminase level. In terms of renal function, GA decreased serum urea level but the effect was not sustained after the first month.

Conclusion

GA may alter the disease severity in SCA as demonstrated by its ability to decrease direct bilirubin and urea levels in the serum.

Prevalence and factors associated with renal dysfunction in children admitted to two hospitals in northwestern Tanzania

BACKGROUND

It is evident that renal dysfunction (RD) is associated with unique infectious and non-infectious causes in African children. However, little data exists about the prevalence and factors associated with RD in children admitted to African hospitals.

METHODS

In this cross-sectional study, we enrolled all children admitted to pediatric wards of Bugando Medical Centre (BMC) and Sekou-Toure Regional Referral hospital (SRRH) during a 6 month time period. Socio-demographical, clinical and laboratory data were collected using a structured questionnaire. Estimated glomerular filtration rate (eGFR) was calculated using modified Schwartz equation and those with < 60 ml/min/1.73m2were considered to have RD. Data analysis was done using STATA version 13 and considered significant when p-value was < 0.05.

RESULTS

A total of 513 children were enrolled, of which 297 (57.9%) were males. Median age of children with and without RD was 34 months (27-60) and 46.5 (29-72) respectively. Prevalence of RD was 16.2%. Factors associated with RD were herbal medication use (p = 0.007), history of sore throat or skin infection (p = 0.024), sickle cell disease (SCD) (p = 0.006), dehydration (p = 0.001), malaria (p = 0.01) and proteinuria (p = < 0.001).

CONCLUSIONS

High prevalence of RD was observed among children admitted to referral hospitals in Mwanza. Screening for RD should be performed on admitted children, particularly those with history of herbal medication use, sore throat/skin infection, SCD, dehydration and malaria. Where creatinine measurement is not possible, screening for proteinuria is a reasonable alternative.

Chronic Kidney Disease amongst Sickle Cell Anaemia Patients at the University of Maiduguri Teaching Hospital, Northeastern Nigeria: A Study of Prevalence and Risk Factors

Background

Involvement of the kidneys in patients with sickle cell anaemia is a well recognised chronic complication. This study seeks to determine the prevalence of chronic kidney disease in patients with homozygous sickle cell disease (HbSS) and to identify risk factors associated with its development.

Methodology

The subjects consisted of adolescents and adults with HbSS recruited sequentially from the adult haematology outpatient clinic and Daycare ward of the unit. Clinical variables including age at diagnosis of SCA, the frequency of vaso-occlusive crisis and transfusion therapy, as well as laboratory data including haematological profile and renal function tests were obtained. The glomerular filtration rate was estimated (eGFR) using the ‘modification of diet in renal disease’ (MDRD) formula.

Results

Two hundred and eighty-four HbSS patients were recruited. The prevalence of CKD amongst them was 38.9%. Further stratification of the patients based on eGFR showed that sixty-nine (26.8%) had hyperfiltration; 35 (13.6%) stage 1 CKD; 53 (20.6%) stage 2 CKD; 33 (12.8%) stage 3a CKD; 28 (10.9%) stage 3b CKD; 30 (11.7%) stage 4 CKD and 9 (3.5%) had end stage renal disease. There was significant association between eGFR and clinical parameters such as age (r −0.353, p=0.000), SBP (r −0.148, p= 0.021), DBP (r −0.213, p=0.001) and total number of blood received (r −0.276, p=0.000); and laboratory parameters such as PCV (r 0.371, p=0.000); urea ( r 0.527, p=000); creatinine (r 0.625, p=0.000) and uric acid ( r −0.419, p=0.000).

Conclusions

The present study has revealed a high prevalence of CKD amongst patients with SCA in our region. Clinical and laboratory predictors of CKD using eGFR were identified to include age, SBP, number of units of blood transfusion, PCV, urea, creatinine and uric acid levels.

Evaluating risk factors for chronic kidney disease in pediatric patients with sickle cell anemia

BACKGROUND

Patients with sickle cell anemia (SCA) have an increased prevalence of nephropathy and mortality from chronic kidney disease (CKD).

METHODS

We evaluated the association of hyperuricemia and nocturnal hypertension with lower estimated glomerular filtration rate (eGFR) using cystatin-C in patients aged 10-21 years with the HbSS or HbSB0 form of the disease during a non-acute clinic visit. eGFR and uric acid measurements were obtained in 83 and 81 participants, respectively, and 24-h ambulatory blood pressure monitoring (ABPM) was performed in 44 participants. Annual testing included vital signs, complete blood count, comprehensive metabolic panel, medications, urine microalbumin/creatinine, and lactate dehydrogenase measurements. Hyperuricemia was defined as a uric acid level of ≥5.5 mg/dL. Nocturnal hypertension was defined as >25% of nocturnal readings at >95th percentile according to norms established by the American Heart Association Statement on ABPM in children and adolescents.

RESULTS

The mean eGFR was statistically significantly lower in patients with hyperuricemia than in those with normal uric acid levels (143 vs. 161 mL/min/1.73 m², respectively). Of the 44 participants for whom ABPM data were available, 14 (32%) had systolic nocturnal hypertension and 12 (27%) had diastolic nocturnal hypertension. The mean eGFR was statistically significantly lower in participants with nocturnal systolic and diastolic hypertension than in those with normal nocturnal blood pressure. In a regression model, nocturnal hypertension and hyperuricemia were associated with a lower eGFR.

CONCLUSIONS

Two risk factors for CKD, i.e., nocturnal hypertension and hyperuricemia, were associated with lower eGFR in older children and adolescent patients with SCA. Long-term studies on their association with progression to CKD in this population are warranted.

KEY POINT

Nocturnal hypertension and hyperuricemia are established risk factors for nephropathy in other diseases and may play a role in SCA nephropathy.

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.

Clinical and genetic predictors of renal dysfunctions in sickle cell anaemia in Cameroon

Micro-albuminuria and glomerular hyperfiltration are primary indicators of renal dysfunctions in Sickle Cell Disease (SCD), with more severe manifestations previously associated with variants in APOL1 and HMOX1 among African Americans. We have investigated 413 SCD patients from Cameroon. Anthropometric variables, haematological indices, crude albuminuria, albumin-to-creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR) were measured. Patients were genotyped for 3·7 kb alpha-globin gene (HBA1/HBA2) deletion, and for variants in APOL1 (G1/G2; rs60910145, rs73885319, rs71785313) and HMOX1 (rs3074372, rs743811). The median age was 15 years; the majority presented with micro-albuminuria (60·9%; n = 248), and approximately half with glomerular hyperfiltration (49·5%; n = 200). Age, male sex, haemoglobin level, leucocyte count, mean corpuscular volume, blood pressure, body mass index and creatinine levels significantly affected albuminuria and/or eGFR. Co-inheritance of alpha-thalassaemia was protective against macro-albuminuria (P = 0·03). APOL1 G1/G2 risk variants were significantly associated with the ACR (P = 0·01) and borderline with eGFR (P = 0·07). HMOX1 - rs743811 was borderline associated with micro-albuminuria (P = 0·07) and macro-albuminuria (P = 0·06). The results revealed a high proportion of micro-albuminuria and glomerular hyperfiltration among Cameroonian SCD patients, and support the possible use of targeted genetic biomarkers for risks assessment.

Glomerular hyperfiltration is strongly correlated with age in Congolese children with sickle cell anaemia

AIM

Glomerular hyperfiltration is an early marker of sickle cell nephropathy and can lead to microalbuminuria and renal failure. Our aim was to identify the associated risk factors, as these could be of preventative importance.

METHODS

We recruited 150 children with sickle cell anaemia (SCA), aged two to 18 years and living in Kinshasa, the Democratic Republic of Congo. Hyperfiltration and microalbuminuria were defined as an estimated glomerular filtration rate of less than 140 mL/min/1.73 m² and an albumin creatinine ratio of between 30 and 299 mg/g, respectively. Independent determinants of hyperfiltration were assessed using logistic regression analysis.

RESULTS

Glomerular hyperfiltration was observed in 60 (40%) children, who were significantly older (10.2 ± 4.1 versus 7.9 ± 4.3 years, p = 0.001) and had a lower body mass index level (14.7 ± 2.3 versus 15.0 ± 2.3 kg/m² ) than the 60% without. A higher proportion had microalbuminuria (25.0 versus 13.3%), but the difference was not statistically significant (p>0.05). Increased age and decreased body mass index were the main independent factors associated with glomerular hyperfiltration in the multivariate analysis. A quarter (25%) of the 60 children with SCA with glomerular hyperfiltration had microalbuminuria.

CONCLUSION

Glomerular hyperfiltration was a common finding in this study and was significantly associated with age.

Clinical phenotypes and the biological parameters of Congolese patients suffering from sickle cell anemia: A first report from Central Africa

BACKGROUND

The influence of phenotype on the clinical course and laboratory features of sickle cell anemia (SCA) is rarely described in sub-Saharan Africa.

METHODS

A cross-sectional study was conducted in Kinshasa. A clinical phenotype score was built up. The following definitions were applied: asymptomatic clinical phenotype (ACP; score≤5), moderate clinical phenotype (MCP; score between 6 and 15), and severe clinical phenotype (SCP; score≥16). ANOVA test were used to compare differences among categorical variables.

RESULTS

We have studied 140 patients. The mean body mass index (BMI) value of three groups was lower (<25 kg/m² ) than the limit defining overweight. BMI of the subjects with ACP was significantly higher than those of other phenotypes (P<.05). Sickle cell patients with ACP have a high mean steady-state hemoglobin concentration compared to those with MCP and SCP (P<.001). A significant elevated baseline leukocyte count is associated with SCP (P<.001). Fetal Hemoglobin (HbF) was significantly higher in ACP. Significant elevation of alpha 1 and alpha 2 globulins in SCP were observed.

CONCLUSION

In our study, fetal hemoglobin has an influence on the clinical severity and the biological parameters of SCA. The study provides data concerning the sickle cell anemia clinical and biological variability in our midst.