Nonlinear trajectory of GFR in children before RRT

GFR decline in patients with CKD has been widely approximated using linear models, but this linearity assumption is not well validated. We conducted a matched case-control study in children from the Chronic Kidney Disease in Children (CKiD) cohort ages 1-16 years with mild to moderate CKD to assess whether GFR decline follows a nonlinear trajectory as CKD approaches ESRD. Children (n=125) who initiated RRT (cases) during follow-up were individually matched by CKD stage at baseline and glomerular/nonglomerular diagnosis with children (n=125) who remained RRT-free when the corresponding case initiated RRT (controls). GFR trajectories were compared using log-linear and piecewise log-linear mixed effects models adjusted for baseline characteristics. From study entry to 18 months before RRT, GFR declined 7% faster among cases compared with controls. However, GFR declined 26% faster among cases compared with controls (P<0.001) during the 18 months before RRT. Nonlinearity in the rate of kidney function loss, which was shown in this cohort, may preclude accurate clinical prediction of the timing of RRT and adequate patient preparation. This study should prompt the characterization of predictive factors that may contribute to an acceleration of kidney function decline.

Vitamin D, race, and risk for anemia in children

OBJECTIVE

To examine the association between 25-hydroxyvitamin D [25(OH)D] deficiency and anemia in a cohort of otherwise-healthy children and to determine whether race modifies the association between 25(OH)D status and hemoglobin (Hgb).

STUDY DESIGN

Cross-sectional study of 10,410 children and adolescents ages 1-21 years from the 2001-2006 National Health and Nutrition Examination Survey. Anemia was defined as Hgb less than the 5th percentile for age and sex based on National Health and Nutrition Examination Survey III (1988-1994) data.

RESULTS

Lower 25(OH)D levels were associated with increased risk for anemia; <30 ng/mL, adjusted OR 1.93, 95% CI 1.21-3.08, P = .006, and <20 ng/mL, OR 1.47, 95% CI 1.14-1.89, P = .004. In linear regression, small but significant increases in Hgb were noted in the upper quartiles of 25(OH)D compared with the lowest quartile (<20 ng/mL) in the full cohort. Results of race-stratified linear regression by 25(OH)D quartile in white children were similar to those observed in the full cohort, but in black children, an increase in Hgb in the upper 25(OH)D quartiles was only apparent compared with the lowest black race-specific quartile (<12 ng/mL).

CONCLUSION

25(OH)D deficiency is associated with increased risk of anemia in healthy US children, but the 25(OH)D threshold levels for lower Hgb are lower in black children in comparison with white children.

Renal parenchymal area and risk of ESRD in boys with posterior urethral valves

BACKGROUND AND OBJECTIVES

Approximately 20% of boys with posterior urethral valves develop ESRD; however, few factors associated with the risk of ESRD have been identified. The objective of this study was to determine if renal parenchymal area, defined as the area of the kidney minus the area of the pelvicaliceal system on first postnatal ultrasound, is associated with the risk of ESRD in infants with posterior urethral valves.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A retrospective cohort of boys who were diagnosed with posterior urethral valves at less than 6 months of age between 1988 and 2011 and followed for at least 1 year at a free-standing children's hospital was assembled. Cox proportional hazard regression and Kaplan-Meier analysis were used to estimate the association between renal parenchymal area and time to ESRD. Cox models were adjusted for age at presentation, minimum creatinine 1 month after bladder decompression, and vesicoureteral reflux.

RESULTS

Sixty patients were followed for 393 person-years. Eight patients developed ESRD. Median renal parenchymal area was 15.9 cm(2) (interquartile range=13.0-21.6 cm(2)). Each 1-cm(2) increase in renal parenchymal area was associated with a lower risk of ESRD (hazard ratio, 0.64; 95% confidence interval, 0.42 to 0.98). The rate of time to ESRD was 10 times higher in boys with renal parenchymal area<12.4 cm(2) than boys with renal parenchymal area≥12.4 cm(2) (P<0.001). Renal parenchymal area could best discriminate children at risk for ESRD when the minimum creatinine in the first 1 month after bladder decompression was between 0.8 and 1.1 mg/dl.

CONCLUSION

In boys with posterior urethral valves presenting during the first 6 months of life, lower renal parenchymal area is associated with an increased risk of ESRD during childhood. The predictive ability of renal parenchymal area, which is available at time of diagnosis, should be validated in a larger, prospectively-enrolled cohort.

Disordered FGF23 and mineral metabolism in children with CKD

BACKGROUND AND OBJECTIVES

In children with CKD, information is limited regarding the prevalence and determinants of fibroblast growth factor 23 excess and 1,25-dihyroxyvitamin D deficiency across the spectrum of predialysis CKD. This study characterized circulating concentrations of fibroblast growth factor 23 and 1,25-dihyroxyvitamin D, and investigated their interrelationships and associations with GFR and secondary hyperparathyroidism in children with CKD who were enrolled in the Chronic Kidney Disease in Children observational cohort study.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Plasma fibroblast growth factor 23 concentrations and determinants of mineral metabolism were measured in 464 children ages 1-16 years with predialysis CKD. GFR was measured by plasma disappearance of iohexol in 70% of participants and estimated by the Chronic Kidney Disease in Children estimating equation using serum creatinine and cystatin C concentrations in the remainder of the participants. Participants were grouped according to CKD stage and by 10-ml/min categories of GFR.

RESULTS

Median GFR for the cohort was 45 ml/min per 1.73 m(2) (interquartile range=33-57; range=15-109). Plasma fibroblast growth factor 23 concentration was above the normal range in 67% of participants (with higher levels observed among participants with lower GFR) before higher levels of serum parathyroid hormone and phosphorus were observed. Plasma fibroblast growth factor 23 levels were 34% higher in participants with glomerular disease than in participants with nonglomerular disease, despite similar GFR. Serum phosphorus levels, adjusted for age, were significantly lower at GFR of 60-69 ml/min per 1.73 m(2) than higher GFR, but thereafter they became higher in parallel with fibroblast growth factor 23 as GFR declined. Serum 1,25-dihyroxyvitamin D concentrations were lower in those participants with low GFR values, high fibroblast growth factor 23 levels, 25-hydroxyvitamin D deficiency, and proteinuria. Secondary hyperparathyroidism was present in 55% of participants with GFR<50 ml/min per 1.73 m(2).

CONCLUSION

In children with predialysis CKD, high plasma fibroblast growth factor 23 is the earliest detectable abnormality in mineral metabolism, and levels are highest in glomerular diseases.

Association of income level with kidney disease severity and progression among children and adolescents with CKD: a report from the Chronic Kidney Disease in Children (CKiD) Study

BACKGROUND

Among adults, lower socioeconomic status (SES) is a risk factor for chronic kidney disease (CKD), progression to end-stage renal disease, and poor health outcomes; but its impact on young people with CKD is not established.

STUDY DESIGN

Prospective cohort study.

SETTINGS & PARTICIPANTS

572 children and adolescents aged 1-16 years with mild to moderate CKD residing in the United States and Canada who were enrolled in the Chronic Kidney Disease in Children (CKiD) Study.

PREDICTOR

Self-reported annual household income category as a proxy measure for SES: ≥$75,000 (high income), $30,000 to <$75,000 (middle income) and <$30,000 (low income).

OUTCOMES & MEASUREMENTS

Clinical characteristics and CKD severity at baseline (glomerular filtration rate [GFR] and comorbid conditions related to disease severity and management) and longitudinally (GFR decline and changes in blood pressure z scores and height z scores per year).

RESULTS

At baseline, low and middle household incomes, compared to high income, were associated with minority race (39% and 20% vs. 7%), lower maternal education (28% and 5% vs. 1%), abnormal birth history (34% and 32% vs. 21%), and having at least one clinical comorbid condition (66% and 64% vs. 55%). Baseline median GFRs were similar across income categories (43-45 mL/min/1.73 m2). After adjusting for baseline differences, average GFR declines per year for the low-, middle-, and high-income categories were -2.3%, -2.7%, and -1.9%, respectively, and were not statistically significantly different among groups. Blood pressure control tended to improve in all groups (z score, -0.10 to -0.04) but higher income was associated with a faster improvement. Each group showed similar deficits in height at baseline. Height deficits diminished over time for participants from high-income families, but not among those from low-income families (z scores for height per year, 0.05 and -0.004, respectively; P = 0.03 for comparison of high and low income).

LIMITATIONS

Income is an imperfect measure for SES; CKiD participants are not representative of children and adolescents with CKD who are uninsured or not receiving care; statistical power to detect associations by income level is limited.

CONCLUSIONS

GFR decline was similar across income groups but better improvement in BP was observed among those with high income. Children and adolescents with CKD from lower income households are at higher risk of impaired growth.

Medication treatment complexity and adherence in children with CKD

BACKGROUND AND OBJECTIVES

The complexity of CKD management in children is increased by the number of comorbid conditions. This study assessed the prevalence of comorbidities in pediatric CKD and the frequency with which multiple comorbidities present together by assessing prevalent medication use by CKD stage and diagnosis and their association with clinical or sociodemographic factors. The association between number and frequency of dosing of medications prescribed and self-report of nonadherence was also assessed.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this cross-sectional analysis of the Chronic Kidney Disease in Children study, medication use at study entry grouped by indication was examined by CKD stage, diagnosis, age, race, ethnicity, income, and CKD duration. Multivariate adjusted predictors of medication use and clustering were examined. Nonadherence was assessed by self-report of missed medications in the past 7 days.

RESULTS

The 558 eligible participants had a median age of 11 years and median GFR of 44 ml/min per 1.73 m(2); 62% of participants were male and 78% had nonglomerular kidney disease. The number of medications for treatment of CKD comorbidities increased with advanced CKD stage (2.5-fold for stages IV versus II; P<0.001) and glomerular disease (1.4-fold versus nonglomerular; P<0.001). Three distinct medication clusters were identified that corresponded to treatment of glomerular disease, advanced renal tubular dysfunction, and proteinuric complications, respectively. Nonadherence was associated with increased medication dosing frequency (administration >2 times/d; P<0.001) but not the number of medications.

CONCLUSIONS

Medical therapy for children with CKD is complex and is affected by glomerular diagnosis, CKD stage, and medication frequency. The need for CKD-related medication treatment cannot be easily predicted by CKD staging alone. Poorer adherence was associated with increased medication frequency, but not with the number of medical problems needing treatment. Consolidating medical treatment and reducing medication frequency may improve adherence rates in children with CKD.

End-stage kidney disease after pediatric nonrenal solid organ transplantation

OBJECTIVES

Adult solid organ transplant (SOT) recipients commonly develop advanced kidney disease; however, the burden of end-stage kidney disease (ESKD) in children after SOT is not well-described. The objectives of this study were to determine the incidence of ESKD after pediatric SOT and the relative risk by SOT type.

METHODS

Retrospective multicenter cohort study of children, ages ≤ 18 years, who received SOTs from 1990 through 2010 using Scientific Registry of Transplant Recipients data linked to the US Renal Data System. We performed a competing risks analysis to determine cumulative incidence of ESKD (chronic dialysis or kidney transplant), treating death as a competing risk, and fit a multivariable Cox regression model to assess hazard of ESKD by organ type.

RESULTS

The cohort included 16,604 pediatric SOT recipients (54% liver, 34% heart, 6% lung, 6% intestine, and 1% heart-lung). During a median follow-up of 6.2 years (interquartile range 2.2-12.1), 426 (3%) children developed ESKD. Compared with liver transplant recipients, in whom the incidence of ESKD was 2.1 cases per 1000 person-years, in adjusted analyses the highest risk of ESKD was among intestinal (hazard ratio [HR] 7.37, P < .001), followed by lung (HR 5.79, P < .001) and heart transplant recipients (HR 1.79, P < .001).

CONCLUSIONS

In a 20-year national cohort of pediatric SOT recipients, the risk of ESKD was highest among intestinal and lung transplant recipients. The burden of earlier stages of chronic kidney disease is probably much higher; modifiable risk factors should be targeted to prevent progressive kidney damage in this high-risk population.

Nephrotic-range proteinuria is strongly associated with poor blood pressure control in pediatric chronic kidney disease

Despite the importance of blood pressure (BP) control in chronic kidney disease (CKD), few longitudinal studies on its trends exist for pediatric patients with CKD. Here we longitudinally analyzed casual data in 578 children with CKD and annual BP measurements standardized for age, gender and height. At baseline, 124 children were normotensive, 211 had elevated BP and 243 had controlled hypertension. Linear mixed effects models accounting for informative dropout determined factors associated with BP changes over time and relative sub-hazards (RSH) identified factors associated with the achievement of controlled BP in children with baseline elevated BP. Younger age, black children, higher body mass index, and higher proteinuria at baseline were associated with higher standardized BP levels. Overall average BP decreased during follow-up, but nephrotic range proteinuria, and increased proteinuria and body mass index were risk factors for increasing BP over time. Only 46% of hypertensive patients achieved controlled BP during follow-up; least likely were those with nephrotic range proteinuria (RSH 0.19), black children (RSH 0.42) and children with baseline GFR under 40 ml/min/1.73m² (RSH 0.58). Thus, of many coexisting factors, nephrotic range proteinuria was most strongly associated with poor BP control and worsening BP over time. Future research should focus on strategies to reduce proteinuria, as this may improve BP control and slow the progression of CKD.

The impact of short stature on health-related quality of life in children with chronic kidney disease

OBJECTIVES

To compare the health-related quality of life (HRQoL) of children with chronic kidney disease (CKD) and short stature (SS) with that of children with CKD and normal height (NH), to evaluate the impact of catch-up growth and growth hormone (GH) use on HRQoL, and to describe the concordance of perceptions of HRQoL between children with SS and NH and their parents.

STUDY DESIGN

Four hundred eighty-three children and/or parents enrolled in the multicenter Chronic Kidney Disease in Children study who had completed the Pediatric Quality of Life Inventory (Version 4.0) on at least 2 Chronic Kidney Disease in Children study visits composed this substudy population. Participants were dichotomized into NH or SS groups. The demographic characteristics that varied at baseline (sex, glomerular filtration rate, and parent education) were controlled for in the main analysis evaluating the impact of catch-up growth and use of GH on HRQoL.

RESULTS

Multivariate modeling (controlling for confounding variables) revealed a significant association between both catch-up growth and GH use on parent-proxy reports of child physical functioning (P < .05) and social functioning (P < .05). Older children with CKD (15-17 years old) had significantly higher ratings than their parents on the Pediatric Quality of Life Inventory Physical, Emotional, Social, and School Functioning scales compared with younger children (8-14 years old).

CONCLUSION

The finding that height gains and GH use are associated with increases in physical and social functioning by parent report provides additional support for interventions to improve height in children with CKD. The importance of evaluating both the parent and child perceptions of HRQoL is supported by our results.

Blood lead level and measured glomerular filtration rate in children with chronic kidney disease

BACKGROUND

The role of environmental exposure to lead as a risk factor for chronic kidney disease (CKD) and its progression remains controversial, and most studies have been limited by a lack of direct glomerular filtration rate (GFR) measurement.

OBJECTIVE

We evaluated the association between lead exposure and GFR in children with CKD.

METHODS

In this cross-sectional study, we examined the association between blood lead levels (BLLs) and GFR measured by the plasma disappearance of iohexol among 391 participants in the Chronic Kidney Disease in Children (CKiD) prospective cohort study.

RESULTS

Median BLL and GFR were 1.2 µg/dL and 44.4 mL/min per 1.73 m2, respectively. The average percent change in GFR for each 1-µg/dL increase in BLL was -2.1 (95% CI: -6.0, 1.8). In analyses stratified by CKD diagnosis, the association between BLL and GFR was stronger among children with glomerular disease underlying CKD; in this group, each 1-µg/dL increase in BLL was associated with a -12.1 (95% CI: -22.2, -1.9) percent change in GFR. In analyses stratified by anemia status, each 1-µg/dL increase in BLL among those with and without anemia was associated with a -0.3 (95% CI: -7.2, 6.6) and -4.6 (95% CI: -8.9, -0.3) percent change in GFR, respectively.

CONCLUSIONS

There was no significant association between BLL and directly measured GFR in this relatively large cohort of children with CKD, although associations were observed in some subgroups. Longitudinal analyses are needed to examine the temporal relationship between lead and GFR decline, and to further examine the impact of underlying cause of CKD and anemia/hemoglobin status among patients with CKD.

Echo-Doppler assessment of the biophysical properties of the aorta in children with chronic kidney disease

Chronic kidney disease (CKD) is known to cause increased arterial stiffness, which is an important independent risk factor for adverse cardiovascular events. The purpose of this study was to assess the vascular properties of the aorta (AO) in a group of children with CKD using a noninvasive echocardiography (echo)-Doppler method. We studied 24 children with stages 2 through 5 CKD and 48 age-matched controls. Detailed echocardiographic assessment and echo-Doppler pulse wave velocity (PWV) was performed. Indices of arterial stiffness, including characteristic (Zc) and input (Zi) impedances, elastic pressure-strain modulus (Ep), and arterial wall stiffness index, were calculated. CKD patients underwent full nephrology assessment, and an iohexol glomerular filtration rate was performed, which allowed for accurate assignment of the CKD stage. CKD patients had greater median systolic blood pressure (114 vs. 110 mmHg; p < 0.04) and pulse pressure (51 vs. 40 mmHg; p < 0.001) compared with controls. PWV was similar between groups (358 vs. 344 cm s(-1); p = 0.759), whereas Zi (182 vs. 131 dyne s cm(-5); p < 0.001), Zc (146 vs. 138 dyne s cm(-5); p = 0.05), and Ep (280 vs. 230 mmHg; p < 0.02) were significantly greater in CKD than in controls. Although load-dependent measures of arterial stiffness were greater in non-dialysis dependent CKD patients, PWV was not increased compared with controls. This suggests that the increased arterial stiffness may not be permanent in these pediatric patients with kidney disease.

Systematic review of structural and functional neuroimaging findings in children and adults with CKD

CKD has been linked with cognitive deficits and affective disorders in multiple studies. Analysis of structural and functional neuroimaging in adults and children with kidney disease may provide additional important insights into the pathobiology of this relationship. This paper comprehensively reviews neuroimaging studies in both children and adults. Major databases (PsychLit, MEDLINE, WorldCat, ArticleFirst, PubMed, Ovid MEDLINE) were searched using consistent search terms, and studies published between 1975 and 2012 were included if their samples focused on CKD as the primary disease process. Exclusion criteria included case reports, chapters, and review articles. This systematic process yielded 43 studies for inclusion (30 in adults, 13 in children). Findings from this review identified several clear trends: (1) presence of cerebral atrophy and cerebral density changes in patients with CKD; (2) cerebral vascular disease, including deep white matter hyperintensities, white matter lesions, cerebral microbleeds, silent cerebral infarction, and cortical infarction, in patients with CKD; and (3) similarities in regional cerebral blood flow between patients with CKD and those with affective disorders. These findings document the importance of neuroimaging procedures in understanding the effect of CKD on brain structure, function, and associated behaviors. Results provide a developmental linkage between childhood and adulthood, with respect to the effect of CKD on brain functioning across the lifespan, with strong implications for a cerebrovascular mechanism contributing to this developmental linkage. Use of neuroimaging methods to corroborate manifest neuropsychological deficits or perhaps to indicate preventive actions may prove useful to individuals with CKD.

Nutritional vitamin D use in chronic kidney disease: a survey of pediatric nephrologists

BACKGROUND

Vitamin D deficiency may contribute to risk of cardiovascular disease, diabetes, and infections, in addition to known effects on mineral metabolism. Controversy remains regarding the use of nutritional vitamin D supplementation in chronic kidney disease (CKD), and the supplementation practices of pediatric nephrologists are unknown.

METHODS

An electronic survey containing eight vignettes was sent to physician members of the International Pediatric Nephrology Association in 2011 to identify physician and patient characteristics that influence nephrologists to supplement CKD patients with nutritional vitamin D. Vignettes contained patient characteristics including light vs dark skin, CKD stage, cause of renal disease, parathyroid hormone (PTH), and 25(OH) vitamin D levels. Multivariate logistic generalized estimating equation regression was used to identify predictors of supplementation.

RESULTS

Of 1,084 eligible physicians, 504 (46%) completed the survey. Supplementation was recommended in 73% of cases overall (ranging from 91% of those with vitamin D levels <10 ng/mL to 35% with levels >30). Greater CKD severity was associated with greater recommendation of supplementation, especially for patients with higher vitamin D levels (test for interaction p < 0.0001). PTH level above target for CKD stage was associated with greater recommendation to supplement in pre-dialysis CKD, but did not have an impact on recommendations in dialysis patients (test for interaction p < 0.0001). Skin color, cause of CKD, and albumin levels were not associated with supplementation recommendation.

CONCLUSIONS

Recommending nutritional vitamin D is common worldwide, driven by CKD stage and vitamin D and PTH levels. Future studies are needed to establish the risks and benefits of supplementation.

An agenda for children for the 113th Congress: recommendations from the pediatric academic societies

The 113th Congress of the United States begins in January 2013. With each new Congress, there are many changes, not only in the faces of the newly elected, but also in the membership of committees and the staff serving the members. As agendas for the session are set, there is a resurgence of conflicting priorities. In the past, when these conflicts were resolved, children were rarely at the top of the list. Given the numerous pressing national issues, both domestic and foreign, the same trend will likely occur.

GWAS of blood cell traits identifies novel associated loci and epistatic interactions in Caucasian and African-American children

Hematological traits are important clinical indicators, the genetic determinants of which have not been fully investigated. Common measures of hematological traits include red blood cell (RBC) count, hemoglobin concentration (HGB), hematocrit (HCT), mean corpuscular hemoglobin (MCH), MCH concentration (MCHC), mean corpuscular volume (MCV), platelet count (PLT) and white blood cell (WBC) count. We carried out a genome-wide association study of the eight common hematological traits among 7943 African-American children and 6234 Caucasian children. In African Americans, we report five novel associations of HBE1 variants with HCT and MCHC, the alpha-globin gene cluster variants with RBC and MCHC, and a variant at the ARHGEF3 locus with PLT, as well as replication of four previously reported loci at genome-wide significance. In Caucasians, we report a novel association of variants at the COPZ1 locus with PLT as well as replication of four previously reported loci at genome-wide significance. Extended analysis of an association observed between MCH and the alpha-globin gene cluster variants demonstrated independent effects and epistatic interaction at the locus, impacting the risk of iron deficiency anemia in African Americans with specific genotype states. In summary, we extend the understanding of genetic variants underlying hematological traits based on analyses in African-American children.

Risk factors for end-stage kidney disease after pediatric liver transplantation

Adult liver transplant (LT) recipients commonly develop advanced kidney disease. However, burden of end-stage kidney disease (ESKD) after pediatric LT has not been well-described. We performed a retrospective cohort study of pediatric LTs in the United States from 1990 to 2010. Multivariable Cox regression models were fit to determine risk factors for ESKD and death. Eight thousand nine hundred seventy six children received LTs. During median follow-up of 7.8 years, 2005 (22%) subjects died (mortality rate 26.1 cases/1000 person-years); 167 (2%) developed ESKD (incidence rate 2.2 cases/1000 person-years). Risk factors for ESKD included older age at LT (highest risk age >15 vs. < 5 years, HR = 4.94, p < 0.001), hepatitis C (HR 2.79, p = 0.004), liver re-transplant (HR 2.67, p < 0.001), eGFR pre-LT < 60 versus ≥ 60 (HR 2.37, p < 0.001), hepatitis B (HR 2.25, p = 0.027), black race (HR 1.46, p = 0.046), and male sex (HR 1.44, p = 0.022). LT recipients with ESKD had increased risk of mortality (HR 2.37, p < 0.001). Among pediatric LT recipients, rate of ESKD was lower than among adults and far exceeded by rate of death, however follow-up time in this study may underestimate lifetime burden of ESKD. Although uncommon, ESKD was highly associated with mortality. Pediatric LT recipients should be routinely monitored for kidney disease, particularly those at highest risk of ESKD.

CKiD (CKD in children) prospective cohort study: a review of current findings

Chronic kidney disease (CKD) is a life-long condition associated with substantial morbidity and premature death due to complications from a progressive decrease in kidney function. The incidence and prevalence of all stages of CKD in children continues to increase worldwide. Between 2000 and 2008, the kidney replacement therapy incidence rate in those aged 0-19 years increased 5.9% to 15 per million population, highlighting the importance of CKD research in children. Many comorbid conditions seen in adults with CKD, including cardiovascular disease and cognitive impairment, also are highly prevalent in children, implicitly demonstrating the crucial need for initiating therapy early to improve health outcomes in children with CKD. The CKiD (Chronic Kidney Disease in Children) Study is a prospective cohort study of 586 children aged 1-16 years with an estimated glomerular filtration rate of 30-90 mL/min/1.73 m(2). Since its inception, CKiD has identified risk factors for CKD progression and cardiovascular disease in children with CKD and highlighted the effects of CKD on outcomes unique to children, including neurocognitive development and growth. This review summarizes the findings to date, illustrating the spectrum of CKD-associated complications in children and emphasizing areas requiring further investigation. Taken in sum, these elements stress that initiating treatment at an early age is essential for reducing long-term morbidity and mortality in children with CKD.

Health related quality of life in adolescents with bladder exstrophy-epispadias as measured by the Child Health Questionnaire-Child Form 87

PURPOSE

We determined health related quality of life as reported by adolescents with bladder exstrophy or epispadias using a validated generic instrument.

MATERIALS AND METHODS

Adolescents age 11 to 18 years with bladder exstrophy or epispadias (57) completed a validated, generic, health related quality of life instrument, the CHQ-CF87 (Child Health Questionnaire-Child Form 87). Urinary incontinence, catheterization status, and medical and surgical history data were also obtained. Mean summary scores and 95% CIs for each subdomain of the CHQ-CF87 were calculated, and descriptively compared to 2 population based samples. In our sample health related quality of life outcomes by continence status were compared using univariate and multivariate analysis. However, this analysis was limited by a small sample size.

RESULTS

Mean age of the 49 patients with bladder exstrophy and the 8 with epispadias was 14.3 years, 67% were male and 81% were Caucasian. There were 31 participants who reported incontinence and the median number of lifetime surgeries was 9. The exstrophy population scored well in all subdomains of the instrument when descriptively compared to 2 large samples of adolescent populations. In our sample incontinent patients had lower scores by multivariate analysis in 7 of 10 domains and better scores in 3 of 10 domains, although these differences were not statistically significant.

CONCLUSIONS

Adolescents with bladder exstrophy and epispadias reported relatively good scores on the CHQ-CF87 when descriptively compared to other reference populations. This finding suggests that these children adapt well to the challenges of their condition. Analysis of the association of incontinence with health related quality of life was limited by the small sample size.

Evaluation of serum creatinine concentration-based glomerular filtration rate equations in pediatric patients with chronic kidney disease

STUDY OBJECTIVE

To evaluate the accuracy of four equations based on serum creatinine concentration-the original Schwartz equation and the Leger, Bedside Chronic Kidney Disease in Children (CKiD), and Counahan-Barratt equations-for determining glomerular filtration rate (GFR) in pediatric patients with chronic kidney disease.

DESIGN

Retrospective, observational, cross-sectional study.

SETTING

Single-center, academic, outpatient pediatric nephrology clinic.

PATIENTS

Fifty-three pediatric patients with stages 2-5 chronic kidney disease who completed GFR assessment with (125) I-iothalamate between January 2002 and January 2005.

MEASUREMENT AND MAIN RESULTS

Data were collected from each patient's medical record. Glomerular filtration rate data were analyzed using 59 evaluations from the 53 pediatric patients. (125) I-iothalamate clearance was used as the index GFR. The Bedside CKiD and Counahan-Barratt equations outperformed the Schwartz and Leger equations when the index GFR was less than 60 ml/minute/1.73 m(2) ; the Schwartz and Counahan-Barratt equations performed best for index GFRs of 60 ml/minute/1.73 m(2) or greater. Overestimation was highest with the Schwartz and Leger equations (> 20% index GFR in 57.6% and 62.7% of patients, respectively). Underestimation was highest with the Bedside CKiD and Counahan-Barratt equations (> 20% index GFR in 30.5% and 28.8%, respectively).

CONCLUSION

The new Bedside CKiD equation performed well for pediatric patients with moderate-to-severe chronic kidney disease, but less well for pediatric patients with mild disease. Additional studies are needed to develop more precise GFR equations using serum creatinine concentration.

Reliability of resting blood pressure measurement and classification using an oscillometric device in children with chronic kidney disease

OBJECTIVE

To compare the reliability of blood pressure (BP) readings obtained with an oscillometric device with those obtained by auscultation and assess for differences in BP status classification based on the 2 techniques.

STUDY DESIGN

Resting BP was measured by auscultation and with an oscillometric device at the same encounter in 235 subjects enrolled in the Chronic Kidney Disease in Children study. Resting auscultatory BP values were averaged and compared with averaged oscillometric readings. BP agreement by the 2 methods was assessed using Bland-Altman plots, and BP status classification agreement was assessed by calculation of kappa statistics.

RESULTS

Oscillometric BP readings were higher than auscultatory readings, with a median paired difference of 9 mm Hg for systolic BP (SBP) and 6 mm Hg for diastolic BP (DBP). Correlation for mean SBP was 0.624 and for mean DBP was 0.491. The bias for oscillometric BP measurement was 8.7 mm Hg for SBP (P < .01) and 5.7 mm Hg for DBP (P < .01). BP status classification agreement was 61% for SBP and 63% for DBP, with Kappa values of .31 for SBP and .20 for DBP.

CONCLUSIONS

Compared with auscultation, the oscillometric device significantly overestimated both SBP and DBP, leading to frequent misclassification of BP status.

Serum adiponectin complexes and cardiovascular risk in children with chronic kidney disease

In contrast to the general population, patients with chronic kidney disease (CKD) experience increased total adiponectin levels despite an increased prevalence of cardiovascular disease. Adiponectin circulates as trimer, low molecular weight (LMW), and high molecular weight (HMW) complexes. The distribution and role of each subfraction in CKD is unknown. This cross-sectional analysis examined the association of serum adiponectin and its subfractions with known cardiovascular risk factors in 105 children (median age 12 years; 56% male) enrolled into the Chronic Kidney Disease in Children (CKiD) study, an observational cohort study of children with CKD stage 2-4.HMW accounted for 46% of total adiponectin, followed by LMW (34%) and trimer (20%). In multivariable analysis, LMW was independently associated with iohexol glomerular filtration rate (GFR) (p = 0.004) and was higher in pubertal versus prepubertal children (p = 0.005). HMW/LMW ratio was independently associated with age and iohexol GFR (all p < 0.001). Unexpectedly, systolic blood pressure was positively correlated with HMW (p = 0.01), and HMW/LMW ratio (p = 0.007) and inversely correlated with LMW (p = 0.009). Among subfractions, only LMW was significantly correlated with left ventricular mass (LVM) index (p = 0.05). In multivariable analysis, decreased LMW was independently associated with higher LVM index [β= -0.25, 95% confidence interval (CI) -0.50, -0.03, p=0.04) after adjustment for body mass index (BMI), age, and blood pressure.The higher total adiponectin levels in children with CKD are associated with higher HMW and lower LMW. This imbalance may be an important biomarker for increased cardiovascular risk despite higher levels of total adiponectin in children with CKD.

Urological disorders in chronic kidney disease in children cohort: clinical characteristics and estimation of glomerular filtration rate

PURPOSE

Urological disorders are the most common cause of pediatric chronic kidney disease. We determined the characteristics of children with urological disorders and assessed the agreement between the newly developed bedside glomerular filtration rate estimating formula with measured glomerular filtration rate in 586 patients in the Chronic Kidney Disease in Children study.

MATERIALS AND METHODS

The Chronic Kidney Disease in Children study is a prospective, observational cohort of children recruited from 48 sites in the United States and Canada. Eligibility requirements include age 1 to 16 years and estimated glomerular filtration rate by original Schwartz formula 30 to 90 ml/min/1.73 m(2). Baseline demographics, clinical variables and glomerular filtration rate were assessed. Bland-Altman analysis was conducted to assess agreement between estimated and measured glomerular filtration rates.

RESULTS

Of the 586 participants with at least 1 glomerular filtration rate measurement 348 (59%) had an underlying urological diagnosis (obstructive uropathy in 118, aplastic/hypoplastic/dysplastic kidneys in 104, reflux in 87 and other condition in 39). Among these patients median age was 9 years, duration of chronic kidney disease was 7 years and age at first visit with a urologist was less than 1 year. Of the patients 67% were male, 67% were white and 21% had a low birth weight. Median height was in the 24th percentile. Median glomerular filtration rate as measured by iohexol plasma disappearance was 44.8 ml/min/1.73 m(2). Median glomerular filtration rate as estimated by the Chronic Kidney Disease in Children bedside equation was 44.3 ml/min/1.73 m(2) (bias = -0.5, 95% CI -1.7 to 0.7, p = 0.44).

CONCLUSIONS

Underlying urological causes of chronic kidney disease were present in 59% of study participants. These children were diagnosed early in life, and many had low birth weight and growth delay. There is good agreement between the newly developed Chronic Kidney Disease in Children estimating equations and measured glomerular filtration rate in this population.

Methods for characterizing differences in longitudinal glomerular filtration rate changes between children with glomerular chronic kidney disease and those with nonglomerular chronic kidney disease

The rate of decline of glomerular filtration rate (GFR) in children with chronic kidney disease (CKD) can vary, even among those with similar diagnoses. Classic regression methods applied to the log-transformed GFR (i.e., lognormal) quantify only rigid shifts in a given outcome. The generalized gamma distribution offers an alternative approach for characterizing the heterogeneity of effect of an exposure on a positive, continuous outcome. Using directly measured GFR longitudinally assessed between 2005 and 2010 in 529 children enrolled in the Chronic Kidney Disease in Children Study, the authors characterized the effect of glomerular CKD versus nonglomerular CKD diagnoses on the outcome, measured as the annualized GFR ratio. Relative percentiles were used to characterize the heterogeneity of effect of CKD diagnosis across the distribution of the outcome. The rigid shift assumed by the classic mixed models failed to capture the fact that the greatest difference between the glomerular and nonglomerular diagnosis' annualized GFR ratios was in children who exhibited the fastest GFR declines. Although this difference was enhanced in children with an initial GFR level of 45 mL/minute/1.73 m(2) or less, the effect of diagnosis on outcome was not significantly modified by level. Generalized gamma models captured heterogeneity of effect more richly and provided a better fit to the data than did conventional lognormal models.

Metabolic abnormalities, cardiovascular disease risk factors, and GFR decline in children with chronic kidney disease

BACKGROUND AND OBJECTIVES

Metabolic abnormalities and cardiovascular disease (CVD) risk factors have rarely been systematically assessed in children with chronic kidney disease (CKD). We examined the prevalence of various CKD sequelae across the GFR spectrum.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data were used from 586 children participating in the Chronic Kidney Disease in Children (CKiD) study (United States and Canada) with GFR measured by iohexol plasma disappearance. Laboratory values and CVD risk factors were compared across GFR categories and with an age-, gender-, and race-matched community sample.

RESULTS

CKiD participants were 62% male, 66% Caucasian, 23% African American, and 15% Hispanic with a median age of 11 years and a median GFR of 44 ml/min per 1.73 m(2). Compared with those with a GFR ≥ 50 ml/min per 1.73 m(2), having a GFR < 30 ml/min per 1.73 m(2) was associated with a three-fold higher risk of acidosis and growth failure and a four- to five-fold higher risk of anemia and elevated potassium and phosphate. Median GFR change was -4.3 ml/min per 1.73 m(2) and -1.5 ml/min per 1.73 m(2) per year in children with glomerular and nonglomerular diagnoses, respectively. Despite medication and access to nephrology care, uncontrolled systolic hypertension was present in 14%, and 16% had left ventricular hypertrophy. Children with CKD frequently were also shorter and had lower birth weight, on average, compared with norms.

CONCLUSIONS

Growth failure, metabolic abnormalities, and CVD risk factors are present at GFR >50 ml/min per 1.73 m(2) in children with CKD and, despite therapy, increase in prevalence two- to four-fold with decreasing GFR.

Insights from the Chronic Kidney Disease in Children (CKiD) study

Over the last 5 years, the Chronic Kidney Disease in Children (CKiD) prospective cohort study has enrolled close to 600 children ages 1 to 16 years with mild to moderate chronic kidney disease (CKD). The main purpose of this interim report is to review the initial cross-sectional data and conclusions derived from the clinical studies conducted within CKiD in the context of findings from other pediatric CKD and end-stage renal disease (ESRD) registry and cohort studies. In particular, special emphasis was placed on studying four aspects of chronic kidney disease in children, including the identification of risk factors related to disease progression, the impact of CKD on neurocognition and quality of life (QoL), the cardiovascular morbidity associated with CKD, and identifying the causes and effects of growth failure in the context of mild to moderate kidney failure.

Neurocognitive functioning of children and adolescents with mild-to-moderate chronic kidney disease

BACKGROUND AND OBJECTIVES

Few data exist on the neurocognitive functioning of children with mild-to-moderate chronic kidney disease (CKD). The primary objectives of this paper are (1) to determine the neurocognitive status in this population and (2) to identify sociodemographic and health-status variables associated with neurocognitive functioning.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a cross-sectional study of 368 children, aged 6 to 16 years, from the Chronic Kidney Disease in Children (CKiD) cohort. Median iGFR was 43 ml/min per 1.73 m(2), and the median duration of CKD was 8.0 years. Approximately 26% had underlying glomerular disease. Measures of intelligence, academic achievement, attention regulation, and executive functioning were obtained at study entry. The prevalence of neurocognitive deficits was determined by comparing participant scores on each measure of neurocognitive functioning with normative data. The association between hypothesized predictors of neurocognitive dysfunction was evaluated using multivariate regression analyses.

RESULTS

Neurocognitive functioning was within the average range for the entire group; however, 21% to 40% of participants scored at least one SD below the mean on measures of intelligence quotient (IQ), academic achievement, attention regulation, or executive functioning. Higher iohexol-based GFR (iGFR) predicted a lesser risk for poor performance on measures of executive function. Participants having elevated proteinuria (i.e., urine protein/creatinine >2) scored lower on verbal IQ, full-scale IQ, and attention variability than those without elevated proteinuria.

CONCLUSIONS

Whereas most children with mild-to-moderate CKD have no major neurocognitive deficits, a substantial percentage did show neurocognitive dysfunction that places them at risk for poor long-term educational and occupational outcomes.

No difference in meeting hemoglobin and albumin targets for dialyzed children with urologic disorders

Urologic disorders are the most common cause of chronic kidney disease in children. To determine whether children with urologic etiology of end-stage renal disease (ESRD) fare better than children with ESRD from other causes while on dialysis, we conducted a cross-sectional study of children <18 years receiving peritoneal and hemodialysis in the United States using data from the Centers for Medicare & Medicaid Services 2005 ESRD CPM Project. We compared baseline demographics and the study groups. In multivariate logistic regression analysis of 1,286 subjects, we assessed whether children with urologic disorders had a higher odds of meeting adult KDOQI targets for hemoglobin levels ≥11 g/dl and albumin ≥3.5 BCG/3.2 BCP g/dl. We conducted a subset analysis of 1,136 patients to examine the impact of erythropoietin on hemoglobin targets. Our results did not reveal differences in achievement of adult hemoglobin targets (adjusted OR: 1.27; p value 0.09; CI: 0.97-1.66) or in the subset analysis with erythropoietin (adjusted OR: 1.32; p value 0.06; CI: 0.98-1.78) or albumin targets (adjusted OR: 1.22; p value 0.21; CI: 0.90-1.65) in adjusted analyses. Due to our study's limitations, it is difficult to determine whether this may result from treatment prior to dialysis initiation or treatment effect of dialysis rather than underlying diagnosis.

Casual blood pressure and neurocognitive function in children with chronic kidney disease: a report of the children with chronic kidney disease cohort study

BACKGROUND AND OBJECTIVES

Children with chronic kidney disease (CKD) are at risk for cognitive dysfunction, and over half have hypertension. Data on the potential contribution of hypertension to CKD-associated neurocognitive deficits in children are limited. Our objective was to determine whether children with CKD and elevated BP (EBP) had decreased performance on neurocognitive testing compared with children with CKD and normal BP.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a cross-sectional analysis of the relation between auscultatory BP and neurocognitive test performance in children 6 to 17 years enrolled in the Chronic Kidney Disease in Children (CKiD) project.

RESULTS

Of 383 subjects, 132 (34%) had EBP (systolic BP and/or diastolic BP ≥90(th) percentile). Subjects with EBP had lower mean (SD) scores on Wechsler Abbreviated Scales of Intelligence (WASI) Performance IQ than those with normal BP (normal BP versus EBP, 96.1 (16.7) versus 92.4 (14.9), P = 0.03) and WASI Full Scale IQ (97.0 (16.2) versus 93.4 (16.5), P = 0.04). BP index (subject's BP/95(th) percentile BP) correlated inversely with Performance IQ score (systolic, r = -0.13, P = 0.01; diastolic, r = -0.19, P < 0.001). On multivariate analysis, the association between lower Performance IQ score and increased BP remained significant after controlling for demographic and disease-related variables (EBP, β = -3.7, 95% confidence interval [CI]: -7.3 to -0.06; systolic BP index, β = -1.16 to 95% CI: -2.1, -0.21; diastolic BP index, β = -1.17, 95% CI: -1.8 to -0.55).

CONCLUSIONS

Higher BP was independently associated with decreased WASI Performance IQ scores in children with mild-to-moderate CKD.

Universal GFR determination based on two time points during plasma iohexol disappearance

An optimal measurement of glomerular filtration rate (GFR) should minimize the number of blood draws, and reduce procedural invasiveness and the burden to study personnel and cost, without sacrificing accuracy. Equations have been proposed to calculate GFR from the slow compartment separately for adults and children. To develop a universal equation, we used 1347 GFR measurements from two diverse groups consisting of 527 men in the Multicenter AIDS Cohort Study and 514 children in the Chronic Kidney Disease in Children cohort. Both studies used nearly identical two-compartment (fast and slow) protocols to measure GFR. To estimate the fast component from markers of body size and of the slow component, we used standard linear regression methods with the log-transformed fast area as the dependent variable. The fast area could be accurately estimated from body surface area by a simple parameter (6.4/body surface area) with no residual dependence on the slow area or other markers of body size. Our equation measures only the slow iohexol plasma disappearance curve with as few as two time points and was normalized to 1.73 m2 body surface area. It is of the form: GFR=slowGFR/[1+0.12(slowGFR/100)]. In a random sample utilizing a third of the patients for validation, there was excellent agreement between the calculated and measured GFR with low root mean square errors being 4.6 and 1.5 ml/min per 1.73 m2 for adults and children, respectively. Thus, our proposed simple equation, developed in a combined patient group with a broad range of GFRs, may be applied universally and is independent of the injected amount of iohexol.

Pediatric GFR estimating equations applied to adolescents in the general population

BACKGROUND AND OBJECTIVES

We examined the distribution of estimated GFR (eGFR) in a healthy cohort of adolescents to inform clinical and research use.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Various creatinine-based (n = 3256) and/or cystatin C-based (n = 811) equations, including the recently developed complete and bedside equations from the Chronic Kidney Disease in Children (CKiD) study, were applied to U.S. adolescents 12 to 17 years of age participating in the 1999-2002 National Health and Nutrition Examination Survey (NHANES).

RESULTS

The median serum creatinine and cystatin C were 0.7 mg/dl and 0.83 mg/L, respectively. The distribution of eGFR varied widely, with the median GFR ranging from a low of 96.6 ml/min per 1.73 m(2) (CKiD) to a high of 140.0 ml/min per 1.73 m(2) (original Schwartz). The proportions of participants with eGFRs <75 ml/min per 1.73 m(2) are as follows: bedside CKiD 8.9%, Counahan 6.3%, Leger 0.4%, original Schwartz 0%, Filler 1.3%, Grubb 3.1%, Bouvet 2.5%, CKiD 1.8%, and Zappitelli 5.6%. By any equation examined, no group of participants with eGFR ≤10th percentile had an increased prevalence of comorbid conditions consistent with a low measured GFR.

CONCLUSIONS

Most pediatric-specific GFR estimating equations resulted in 25% to 50% of the participants having an eGFR <100 ml/min per 1.73 m(2). However, participants with eGFR in the lower ranges did not have an increased prevalence of morbidities associated with chronic kidney disease. Clinical validation of creatinine- or cystatin C-based estimated GFRs in healthy children is needed before it is possible to screen the general population for chronic kidney disease.

Extracellular volume and glomerular filtration rate in children with chronic kidney disease

BACKGROUND AND OBJECTIVES

Extracellular volume (ECV) is the fluid contained in all noncellular compartments of the body and is a quantity tightly controlled by the kidney. Thus, there is a strong link between ECV and kidney function.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

The Chronic Kidney Disease in Children (CKiD) study uses injected iohexol to obtain direct measures of GFR. Direct calculation of ECV was viable from GFR studies using descriptors of the disappearance curves. Using linear regression methods on the log-transformed variables, markers of size (height and weight) and biomarkers of kidney disease (serum creatinine, blood urea nitrogen, and cystatin C) were assessed for their relationships with ECV normalized to body weight (ECV/wt). The relationship to hypertension (systolic BP >95th percentile for age, sex, and height) was also assessed.

RESULTS

Data from 790 iohexol studies with medians for GFR=43.4 ml/min per 1.73 m(2), weight=35 kg, and height=1.4 m were used. The median ECV was 8.6 L, and the median ECV/wt was 0.23 L/kg. ECV was found to be a function of height (m) and weight (kg) according to the relationship ECV=√weight×height. Biomarkers of kidney disease yielded significant relationships with ECV/wt, but the strength of association was small. No significant association between ECV/wt and hypertension was found.

CONCLUSIONS

ECV has relevance to studies of chronic kidney disease, is related to biomarkers, and can be easily estimated from the square root of weight and height.

The association between abnormal birth history and growth in children with CKD

BACKGROUND AND OBJECTIVES

Poor linear growth is a well described complication of chronic kidney disease (CKD). This study evaluated whether abnormal birth history defined by low birth weight (LBW; <2500 g), prematurity (gestational age <36 weeks), small for gestational age (SGA; birth weight <10th percentile for gestational age), or intensive care unit (ICU) at birth were risk factors for poor growth outcomes in children with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Growth outcomes were quantified by age-sex-specific height and weight z-scores during 1393 visits from 426 participants of the Chronic Kidney Disease in Children Study, an observational cohort of children with CKD. Median baseline GFR was 42.9 ml/min per 1.73 m(2), 21% had a glomerular diagnosis, and 52% had CKD for ≥ 90% of their lifetime.

RESULTS

A high prevalence of LBW (17%), SGA (14%), prematurity (12%), and ICU after delivery (40%) was observed. Multivariate analyses demonstrated a negative effect of LBW (-0.43 ± 0.14; P < 0.01 for height and -0.37 ± 0.16; P = 0.02 for weight) and of SGA (-0.29 ± 0.16; P = 0.07 for height and -0.41 ± 0.19; P = 0.03 for weight) on current height and weight. In children with glomerular versus nonglomerular diagnoses, the effect of SGA (-1.08 versus -0.18; P = 0.029) on attained weight was more pronounced in children with a glomerular diagnosis.

CONCLUSIONS

LBW and SGA are novel risk factors for short stature and lower weight percentiles in children with mild to moderate CKD independent of kidney function.

Dyslipidemia in children with chronic kidney disease

Dyslipidemia, a known risk factor for atherosclerosis, is frequent among both adults and children with chronic kidney disease. Here, we describe the prevalence and pattern of dyslipidemia from a cross-sectional analysis of 391 children aged 1-16 years, enrolled in the multicenter Chronic Kidney Disease in Children (CKiD) study, with a median glomerular filtration rate (GFR), measured by the plasma disappearance of iohexol, of 43 ml/min per 1.73 m2. Multivariate analysis was applied to adjust for age, gender, body mass index (BMI), GFR, and the urinary protein/creatinine ratio. Proteinuria was in the nephrotic range in 44 and the BMI exceeded the 95th percentile in 57 patients of this cohort. Baseline lipid analysis found a high prevalence of hypertriglyceridemia in 126, increased non-HDL-C in 62, and reduced HDL-C in 83. Overall, 177 children had dyslipidemia, of whom 79 had combined dyslipidemia. Lower GFR was associated with higher triglycerides, lower HDL-C, and higher non-HDL-C. Nephrotic-range proteinuria was significantly associated with dyslipidemia and combined dyslipidemia. Compared with children with a GFR>50, children with a GFR<30 had significantly increased odds ratios for any dyslipidemia or for combined dyslipidemia. Hence, among children with moderate chronic kidney disease, dyslipidemia is common and is associated with lower GFR, nephrotic proteinuria, and non-renal factors including age and obesity.

Parent perspectives of health related quality of life for adolescents with bladder exstrophy-epispadias as measured by the child health questionnaire-parent form 50

PURPOSE

Few groups have examined health related quality of life for adolescents with bladder exstrophy-epispadias. We studied parent reported health related quality of life for adolescents with bladder exstrophy-epispadias using the Child Health Questionnaire-Parent Form 50.

MATERIALS AND METHODS

We recruited 11 to 17-year-old participants with bladder exstrophy-epispadias and their parents. Parents served as proxy respondents for the adolescents by self-administering a validated generic health related quality of life instrument, the Child Health Questionnaire-Parent Form 50. We collected urinary incontinence, catheterization status, and medical and surgical history data. Mean questionnaire scores were compared to population based norms.

RESULTS

Median age of the 55 patients was 14 years, 69% were male and 84% were white. Diagnoses included bladder exstrophy in 48 cases and epispadias in 7. Of the participants 29 (53%) reported urinary incontinence. The median number of lifetime surgeries was 9. Although physical and psychosocial summary measure scores were comparable to norms, the mean general health perception score was significantly worse than that of a population based sample (65.8 points, 95% CI 61.4-70.2 vs 73, 95% CI 71.3-74.7, p = 0.004). Mean family activity and parent emotional impact scores were also significantly worse than in a population based sample (83.6 points, 95% CI 79.3-88.0 vs 89.7, 95% CI 87.9-91.5, p = 0.02 and 67.7, 95% CI 61.9-73.6 vs 80.3, 95% CI 78.4-82.2, p <0.0001, respectively). Comparison of incontinent to continent children revealed a lower mean score on the parent emotional impact scale (62.6 points, 95% CI 55.5-69.8 vs 73.4, 95% CI 63.9-82.9), which approached significance (p = 0.06).

CONCLUSIONS

Although overall adolescent quality of life was comparable to norms, parents reported significantly impaired adolescent general health and family activity as well as a negative parental emotional impact. Further research is needed to identify interventions that can decrease the adverse impact of bladder exstrophy-epispadias on family activity and parent emotional distress.

Hemoglobin differences by race in children with CKD

BACKGROUND

There are known racial disparities in the prevalence of anemia in adults with chronic kidney disease (CKD), but these differences have not been well described in children.

STUDY DESIGN

Cohort study, cross-sectional analysis.

SETTING & PARTICIPANTS

The Chronic Kidney Disease in Children (CKiD) Study is a multicenter prospective cohort study of children with mild to moderate CKD. This analysis included 429 children of African American or white race.

PREDICTOR

Race.

OUTCOMES & MEASUREMENTS

This study examined the association of race with hemoglobin level. Both multiple linear regression and generalized gamma modeling techniques were used to characterize the association between race and hemoglobin level.

RESULTS

79% of the cohort was white, 21% was African American. Neither median hemoglobin level nor frequency of erythropoiesis-stimulating agent use differed by race. In multivariate analysis, lower levels of iohexol-measured glomerular filtration rate, African American race, and glomerular disease (vs nonglomerular disease) as the underlying cause of CKD were independently associated with decreased hemoglobin levels; independent of glomerular filtration rate and CKD diagnosis, African American children had average hemoglobin levels that were 0.6 g/dL (95% CI, -0.9 to -0.2 g/dL) lower than those of white children. Generalized gamma modeling showed that differences in hemoglobin levels observed by race become more pronounced when moving from high to low in the overall hemoglobin level distribution.

LIMITATIONS

Cross-sectional analysis cannot establish causality, and data for iron stores were not available for all patients.

CONCLUSIONS

African American compared with white children have lower hemoglobin values in CKD independent of the underlying cause of CKD. These racial differences in hemoglobin levels appear to increase at the lower end of the hemoglobin level distribution in this population.

Blood lead level and kidney function in US adolescents: The Third National Health and Nutrition Examination Survey

BACKGROUND

Chronic, high-level lead exposure is a known risk factor for kidney disease. The effect of current low-level environmental lead exposure is less well known, particularly among children, a population generally free from kidney disease risk factors such as hypertension and diabetes mellitus. Therefore, in this study, we investigated the association between lead exposure and kidney function in a representative sample of US adolescents.

METHODS

Participants included 769 adolescents aged 12 to 20 years for whom whole blood lead and serum cystatin C were measured in the Third National Health and Nutrition Examination Survey, conducted from 1988-1994. The association between blood lead level and level of kidney function (glomerular filtration rate [GFR]), determined by cystatin C-based and creatinine-based estimating equations, was examined.

RESULTS

Median whole blood lead level was 1.5 microg/dL (to convert to micromoles per liter, multiply by 0.0483), and median cystatin C-estimated GFR was 112.9 mL/min/1.73 m(2). Participants with lead levels in the highest quartile (> or =3.0 microg/dL) had 6.6 mL/min/1.73 m(2)-lower estimated GFR (95% confidence interval, -0.7 to -12.6 mL/min/1.73 m(2)) compared with those in the first quartile (<1 microg/dL). A doubling of blood lead level was associated with a 2.9 mL/min/1.73 m(2)-lower estimated GFR (95% confidence interval, -0.7 to -5.0 mL/min/1.73 m(2)). Lead levels were also associated with lower creatinine-based estimated GFR levels, but the association was weaker than with cystatin C-based GFR and not statistically significant.

CONCLUSIONS

Higher blood lead levels in a range below the current Centers for Disease Control and Prevention-designated level of concern (10 microg/dL) were associated with lower estimated GFRs in a representative sample of US adolescents. This finding contributes to the increasing epidemiologic evidence indicating an adverse effect of low-level environmental lead exposure.

Secondary hyperparathyroidism and anemia in children treated by hemodialysis

BACKGROUND

Many patients treated using hemodialysis remain anemic despite exogenous erythropoietin therapy, suggesting that the anemia experienced by these patients is multifactorial in cause. Iron deficiency, infection, inflammation, and malnutrition have been implicated in this process. Additionally, secondary hyperparathyroidism has been associated with anemia in adults, but few data exist about this topic in children.

STUDY DESIGN

Cross-sectional retrospective.

SETTING & PARTICIPANTS

Children treated in hemodialysis centers (N = 588) within the Centers for Medicare & Medicaid Services' 2002 Clinical Performance Measures Project.

PREDICTOR

Intact parathyroid hormone (iPTH) levels assessed in October, November, and December 2001 and categorized as quintiles.

OUTCOMES & MEASUREMENTS

Achievement of serum hemoglobin level > or = 11 g/dL was assessed using Poisson regression adjusting for sex, age, race, dialysis vintage, vascular access type, single-pool Kt/V, serum albumin level, normalized protein catabolic rate, calcium-phosphorus product, and erythropoietin alfa dose.

RESULTS

Using the second quintile (iPTH, 103-224 pg/mL) as the reference quintile, there was no association between iPTH quintile and achievement of the hemoglobin goal: quintile 1 prevalence ratio, 1.0 (95% CI, 0.9-1.2); quintile 3, 0.95 (95% CI, 0.8-1.1); quintile 4, 0.99 (95% CI, 0.8-1.2); and quintile 5, 0.97 (95% CI, 0.8-1.1). Only serum albumin level >/= 3.5 g/dL (bromocresol green assay method) or > or = 3.2 g/dL (bromocresol purple assay method) was significantly associated with meeting the hemoglobin goal: 1.4 (95% CI, 1.2-1.6).

LIMITATIONS

The simultaneous collection of iPTH and hemoglobin limits causal inference. Iron stores and iron therapy are potential confounders not accounted for in this study.

CONCLUSIONS

In the largest study of this topic in children, no association was found between iPTH level and achievement of a hemoglobin level > or = 11 g/dL. Serum albumin level was associated strongly with achievement of the hemoglobin goal.

Health-related quality of life of children with mild to moderate chronic kidney disease

OBJECTIVE

To compare the health-related quality of life (HRQoL) of children with chronic kidney disease (CKD) with healthy children; to evaluate the association between CKD severity and HRQoL; and to identity demographic, socioeconomic, and health-status variables that are associated with impairment in HRQoL in children with mild to moderate CKD.

METHODS

This was a cross-sectional assessment of HRQoL in children who were aged 2 to 16 and had mild to moderate CKD using the Pediatric Inventory of Quality of Life Core Scales (PedsQL). Overall HRQoL and PedsQL domain means for parents and youth were compared with previously published norms by using independent sample t tests. Study participants were categorized by kidney disease stage (measured by iohexol-based glomerular filtration rate [iGFR]), and group differences in HRQoL were evaluated by using analysis of variance and Cuzick trend tests. The association between hypothesized predictors of HRQoL and PedsQL scores was evaluated with linear and logistic regression analyses.

RESULTS

The study sample comprised 402 participants (mean age: 11 years, 60% male, 70% white, median iGFR: 42.5 mL/min per 1.73 m(2), median CKD duration: 7 years). Youth with CKD had significantly lower physical, school, emotional, and social domain scores than healthy youth. iGFR was not associated with HRQoL. Longer disease duration and older age were associated with higher PedsQL scores in the domains of physical, emotional, and social functioning. Older age was associated with lower school domain scores. Maternal education > or =16 years was associated with higher PedsQL scores in the domains of physical, school, and social functioning. Short stature was associated with lower scores in the physical functioning domain.

CONCLUSIONS

Children with mild to moderate CKD, in comparison with healthy children, reported poorer overall HRQoL and poorer physical, school, emotional, and social functioning. Early intervention to improve linear growth and to address school functioning difficulties is recommended.

Sleep and fatigue symptoms in children and adolescents with CKD: a cross-sectional analysis from the chronic kidney disease in children (CKiD) study

BACKGROUND

Although symptoms of sleepiness and fatigue are common in adults with chronic kidney disease (CKD), little is known about the prevalence of these symptoms in children with CKD.

STUDY DESIGN

Cross-sectional analysis within a cohort study.

SETTING & PARTICIPANTS

We describe the frequency and severity of sleep problems and fatigue and assess the extent of their association with measured glomerular filtration rate (mGFR) and health-related quality of life (HRQOL) in 301 participants of the Chronic Kidney Disease in Children cohort.

OUTCOMES & MEASUREMENTS

Sleep and fatigue-related items from the Pediatric Quality of Life Inventory 4.0 Generic Scales and the CKD-related Symptoms List were used.

RESULTS

Median mGFR was 42.0 mL/min/1.73 m(2) (25th-75th percentiles, 31.2-53.2), and median age was 13.9 years (25th-75th percentiles, 10.8-16.2). Children with mGFR of 40-<50, 30-<40, or <30 mL/min/1.73 m(2) had 2.07 (95% CI, 1.05-4.09), 2.35 (95% CI, 1.17-4.72), and 2.59 (95% CI, 1.15-5.85) higher odds of having more severe parent reports of low energy than children with mGFR > or = 50 mL/min/1.73 m(2). Compared with participants with mGFR > or = 50 mL/min/1.73 m(2), those with mGFR < 30 mL/min/1.73 m(2) had 3.92 (95% CI, 1.37-11.17) higher odds of reporting more severe weakness, and those with mGFR of 40-<50 mL/min/1.73 m(2) had 2.95 (95% CI, 1.26-6.88) higher odds of falling asleep during the day. Low energy, trouble sleeping, and weakness were associated with lower HRQOL scores.

LIMITATIONS

Symptoms of sleep and fatigue represent the child's or parent's perception of symptom severity, whereas individual items can lead to imprecise measurements of sleep and fatigue.

CONCLUSIONS

Lower mGFR was associated with increased weakness, low energy, and daytime sleepiness. Furthermore, a strong association between trouble sleeping, low energy, and weakness with decreases in overall HRQOL was observed. Detection and treatment of poor sleep and fatigue may improve the development and HRQOL of children and adolescents with CKD.

Urinary incontinence in the CKiD cohort and health related quality of life

PURPOSE

Many children with chronic kidney disease have urinary incontinence due to urological disorders and/or a urine concentrating defect. We determined the prevalence and impact of incontinence on health related quality of life in children with chronic kidney disease.

MATERIALS AND METHODS

The Chronic Kidney Disease in Children study is a prospective, observational cohort of children recruited from 47 sites in the United States and Canada. Eligibility requirements are age 1 to 16 years and an estimated glomerular filtration rate of 30 to 90 ml per minute per 1.73 m(2). Demographics, continence status, glomerular filtration rate and physical examination were assessed at study entry. Health related quality of life was measured using the parent and child versions of PedsQL. PedsQL scores in participants 5 years old or older were compared among children who were toilet trained and not bed-wetting, bed-wetting or not toilet trained using multivariate linear regression.

RESULTS

Overall median age of the 329 participants was 12.5 years, 61.4% were male, 70% were white and 55.5% had a urological disorder. Of participants 71.4% were toilet trained at study enrollment, 23.1% had bed-wetting and 5.5% were not toilet trained. Children who were not yet toilet trained had an average total score that was 13.5 points lower (95% CI -25.2, -1.8) on the PedsQL child report than in those who were toilet trained (p = 0.02). Physical functioning (-15.0, 95% CI -28.2, -1.9) and school functioning (-15.3, 95% CI -29.8, -0.8) were also lower in this group (p = 0.03 and 0.04, respectively). On the PedsQL parent proxy report physical functioning (-14.2, 95% CI -26.7, -1.6) was similarly affected by child incontinence (p = 0.03).

CONCLUSIONS

Urinary incontinence is common in pediatric patients with chronic kidney disease and associated with lower health related quality of life on the PedsQL child and parent proxy reports. Early recognition of and treatment for urinary incontinence may improve health related quality of life in this population.

Current advances in chronic kidney disease in children: growth, cardiovascular, and neurocognitive risk factors

Linear growth and neurocognitive development are two of the most important differences between adults and children, in terms of clinical issues that must be addressed in patients with chronic kidney disease (CKD). Correction of metabolic acidosis, nutritional deficiency, and renal osteodystrophy improve linear growth, but many children require administration of growth hormone to achieve normal growth. A variety of neurocognitive deficits occur in children with CKD, although there has been an improvement in outcome via improved dialysis, correction of malnutrition, and decreased aluminum exposure. Although growth and neurocognitive development are delayed, cardiovascular complications are accelerated in children with CKD, and are reflected in a dramatic increase in cardiovascular mortality compared with healthy children. Other early cardiovascular complications in children with CKD include left ventricular hypertrophy, cardiac dysfunction, and vascular calcifications.

Association of proteinuria with race, cause of chronic kidney disease, and glomerular filtration rate in the chronic kidney disease in children study

BACKGROUND AND OBJECTIVES

Proteinuria is associated with chronic kidney disease (CKD), and heavy proteinuria predicts a rapid decline in kidney function. However, the epidemiologic distribution of this important biomarker study is not well described in the pediatric CKD population.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

This cross-sectional study of North American children with CKD examined the association of proteinuria among the baseline clinical variables in the cohort. Urinary protein-to-creatinine ratios (Up/c) were used to measure level of proteinuria.

RESULTS

Of the 419 subjects studied, the median GFR as measured by iohexol disappearance (iGFR) was 42 ml/min per 1.73 m(2), median duration of CKD was six yr, and glomerular diseases accounted for 22% of the CKD diagnoses. Twenty-four percent of children had normal range (Up/c <0.2), 62% had significant, and 14% had nephrotic-range proteinuria (Up/c >2.0). A decrease in iGFR was associated with an increase in Up/c. At any level of GFR, a higher Up/c was associated with a glomerular cause of CKD and non-Caucasian race. Among subjects with a glomerular cause of CKD, Up/c was lower in subjects reporting utilization of renin-angiotensin system (RAS) antagonists (median Up/c = 0.93) compared with those who did not (median Up/c = 3.78).

CONCLUSIONS

Proteinuria is associated with level of iGFR, cause of CKD, and race. The longitudinal study design of Chronic Kidney Disease in Children (CKiD) cohort study and the large number of subjects being studied has created an opportunity to better define the association between proteinuria and CKD progression.

New equations to estimate GFR in children with CKD

The Schwartz formula was devised in the mid-1970s to estimate GFR in children. Recent data suggest that this formula currently overestimates GFR as measured by plasma disappearance of iohexol, likely a result of a change in methods used to measure creatinine. Here, we developed equations to estimate GFR using data from the baseline visits of 349 children (aged 1 to 16 yr) in the Chronic Kidney Disease in Children (CKiD) cohort. Median iohexol-GFR (iGFR) was 41.3 ml/min per 1.73 m(2) (interquartile range 32.0 to 51.7), and median serum creatinine was 1.3 mg/dl. We performed linear regression analyses assessing precision, goodness of fit, and accuracy to develop improvements in the GFR estimating formula, which was based on height, serum creatinine, cystatin C, blood urea nitrogen, and gender. The best equation was: GFR(ml/min per 1.73 m(2))=39.1[height (m)/Scr (mg/dl)](0.516) x [1.8/cystatin C (mg/L)](0.294)[30/BUN (mg/dl)](0.169)[1.099](male)[height (m)/1.4](0.188). This formula yielded 87.7% of estimated GFR within 30% of the iGFR, and 45.6% within 10%. In a test set of 168 CKiD patients at 1 yr of follow-up, this formula compared favorably with previously published estimating equations for children. Furthermore, with height measured in cm, a bedside calculation of 0.413*(height/serum creatinine), provides a good approximation to the estimated GFR formula. Additional studies of children with higher GFR are needed to validate these formulas for use in screening all children for CKD.

New equations to estimate GFR in children with CKD

The Schwartz formula was devised in the mid-1970s to estimate GFR in children. Recent data suggest that this formula currently overestimates GFR as measured by plasma disappearance of iohexol, likely a result of a change in methods used to measure creatinine. Here, we developed equations to estimate GFR using data from the baseline visits of 349 children (aged 1 to 16 yr) in the Chronic Kidney Disease in Children (CKiD) cohort. Median iohexol-GFR (iGFR) was 41.3 ml/min per 1.73 m(2) (interquartile range 32.0 to 51.7), and median serum creatinine was 1.3 mg/dl. We performed linear regression analyses assessing precision, goodness of fit, and accuracy to develop improvements in the GFR estimating formula, which was based on height, serum creatinine, cystatin C, blood urea nitrogen, and gender. The best equation was: GFR(ml/min per 1.73 m(2))=39.1[height (m)/Scr (mg/dl)](0.516) x [1.8/cystatin C (mg/L)](0.294)[30/BUN (mg/dl)](0.169)[1.099](male)[height (m)/1.4](0.188). This formula yielded 87.7% of estimated GFR within 30% of the iGFR, and 45.6% within 10%. In a test set of 168 CKiD patients at 1 yr of follow-up, this formula compared favorably with previously published estimating equations for children. Furthermore, with height measured in cm, a bedside calculation of 0.413*(height/serum creatinine), provides a good approximation to the estimated GFR formula. Additional studies of children with higher GFR are needed to validate these formulas for use in screening all children for CKD.

Patterns of use of vascular catheters for hemodialysis in children in the United States

BACKGROUND

Arteriovenous fistulas (AVFs) and grafts (AVGs) have been associated with improved clinical outcomes in children and adults with end-stage renal disease (ESRD) on maintenance hemodialysis (HD) therapy, but use of vascular catheters is high. Identifying the reasons for the high prevalence of vascular catheters in children on HD therapy is necessary to assess whether targeted interventions may increase the prevalence of AVFs/AVGs.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Children younger than 18 years on HD therapy in the 2001 to 2003 ESRD Clinical Performance Measures (CPM) Projects followed up in the US Renal Data System transplant files through December 31, 2004.

PREDICTOR

Vascular access type and reasons for use of a vascular catheter.

OUTCOMES & MEASUREMENTS

Demographic/clinical characteristics, including the reason provided for use of a vascular catheter, and the association of type of vascular access and (1) patient size and (2) time to kidney transplantation.

RESULTS

Of 1,284 prevalent pediatric CPM patients examined, 529 (41%) had an AVF/AVG and 755 (59%) had a vascular catheter. Of 755 children with a catheter, "small body size" was a commonly listed reason (N = 142); 49% of these children weighed 20 kg or more. Of 53 patients with catheters described as having an "AVF/AVG maturing" and present in the consecutive ESRD CPM project year, 64% had a functioning AVF/AVG the following year. For those with "transplantation scheduled" listed as a reason for a vascular catheter (N = 83), 69% underwent transplantation within 1 year, and median time to transplantation was 115 days. Of all children with vascular catheters (N = 755), 32.2% underwent transplantation within 1 year, and median time to transplantation was 264 days compared with 21.7% and 347 days for those with AVFs/AVGs, respectively (N = 529). Of the 445 incident children in this cohort, 89% had a vascular catheter at dialysis therapy initiation.

LIMITATIONS

Because of study design, only associations can be described.

CONCLUSIONS

Vascular catheter use in children on HD therapy is high. This is partially explained by expeditious transplantation and technical barriers to AVF/AVG placement in small children; however, only one-third of patients with a vascular catheter underwent transplantation within 1 year. Interventions to decrease vascular catheter use in this population may be necessary.

Blood pressure in children with chronic kidney disease: a report from the Chronic Kidney Disease in Children study

To characterize the distribution of blood pressure (BP), prevalence, and risk factors for hypertension in pediatric chronic kidney disease, we conducted a cross-sectional analysis of baseline BPs in 432 children (mean age 11 years; 60% male; mean glomerular filtration rate 44 mL/min per 1.73 m(2)) enrolled in the Chronic Kidney Disease in Children cohort study. BPs were obtained using an aneroid sphygmomanometer. Glomerular filtration rate was measured by iohexol disappearance. Elevated BP was defined as BP >or=90th percentile for age, gender, and height. Hypertension was defined as BP >or=95th percentile or as self-reported hypertension plus current treatment with antihypertensive medications. For systolic BP, 14% were hypertensive and 11% were prehypertensive (BP 90th to 95th percentile); 68% of subjects with elevated systolic BP were taking antihypertensive medications. For diastolic BP, 14% were hypertensive and 9% were prehypertensive; 53% of subjects with elevated diastolic BP were taking antihypertensive medications. Fifty-four percent of subjects had either systolic or diastolic BP >or=95th percentile or a history of hypertension plus current antihypertensive use. Characteristics associated with elevated BP included black race, shorter duration of chronic kidney disease, absence of antihypertensive medication use, and elevated serum potassium. Among subjects receiving antihypertensive treatment, uncontrolled BP was associated with male sex, shorter chronic kidney disease duration, and absence of angiotensin-converting enzyme inhibitor or angiotensin receptor blocker use. Thirty-seven percent of children with chronic kidney disease had either elevated systolic or diastolic BP, and 39% of these were not receiving antihypertensives, indicating that hypertension in pediatric chronic kidney disease may be frequently under- or even untreated. Treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers may improve BP control in these patients.

Health related quality of life in adolescents with abnormal bladder function: an assessment using the Child Health and Illness Profile-Adolescent Edition

PURPOSE

We studied the impact of abnormal bladder function due to congenital urological disorders on health related quality of life in children. A reliable patient based method is needed to assess the impact of these conditions in children and the interventions used to treat them.

MATERIALS AND METHODS

Participants 11 to 17 years old with bladder exstrophy-epispadias complex, spina bifida or other causes of abnormal bladder function self-administered the Child Health and Illness Profile-Adolescent Edition, a generic health related quality of life instrument. They also responded to questions about incontinence, catheterization status and bother level. Mean scores on the profile were compared to population based norms.

RESULTS

Mean age of the 50 participants was 14.9 years, 62% were male and 82% were white. Diagnoses included bladder exstrophy-epispadias complex in 37 patients, spina bifida in 10 and other in 3. The mean +/- SD score on the disorders domain of 14.2 +/- 6.3 was significantly worse than the population norm of 20. Mean scores on the satisfaction, discomfort, resilience, risks and achievement domains were comparable to or better than the population based norm of 20. A total of 29 participants reported incontinence and 31 performed catheterization.

CONCLUSIONS

In this study of adolescents with congenital causes of abnormal bladder function Child Health and Illness Profile-Adolescent Edition generic health related quality of life scores were significantly worse in the disorders domain but largely comparable to or better than those of the general population in other domains. This suggests that the profile may discern between adolescents with structural urological disease and norms but it may not be sensitive enough to fully detect the impact of the condition. Alternatively adolescents may adapt well to the challenges of urological disease.