Cystatin-C levels in healthy children and adolescents: Influence of age, gender, body mass index and blood pressure

Kidney function and renal resistive index in children with juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is a common pediatric rheumatic disease. Renal manifestations have been rarely observed in JIA, although amyloidosis could be a renal complication in systemic JIA (sJIA). To investigate renal damage in JIA children and to establish the relationship with treatment. Blood urea nitrogen (BUN), creatinine, cystatin C (CysC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), urinary albumin excretion (UAE), estimated glomerular filtration rate (eGFR), and renal resistive index (RRI) were assessed in 49 JIA children (9 boys/40 girls, mean age 10.3 ± 3.8 years) and in 49 healthy controls (24 boys/25 girls, mean age 11.3 ± 3.4 years). Twenty-two JIA patients were on methotrexate (MTX) therapy (group A) and 27 on biologic drugs (group B). CysC and BUN (respectively, 0.8 ± 0.1 vs. 0.7 ± 0.1 mg/dl; 13.3 ± 2.9 vs. 11.7 ± 1.4 mg/dl) were higher (p ≤ 0.001) whereas creatinine and eGFR (respectively, 0.5 ± 0.1 vs. 0.6 ± 0.1 mg/dl; 99.2 ± 10.5 vs. 122.5 ± 19.8 ml/min/1.73 m²) were lower in JIA children as compared to controls (p < 0.001). UAE resulted higher in patients than in controls (p = 0.003). Mean RRI was higher in JIA children than controls (0.7 ± 0.04 vs. 0.6 ± 0.04; p < 0.001). Group B showed higher mean RRI than group A (0.7 ± 0.1 vs. 0.7 ± 0.04; p < 0.001). Associations were found between RRI and ESR, JADAS-27, disease state, BMI-SDS (p < 0.001), CRP (p = 0.003) and eGFR (p = 0.001). JIA children had reduced eGFR, increased UAE and higher RRI values, than controls. RRIs were higher in patients on biologic drugs than MTX group and were associated with inflammation indexes and disease state, suggesting a direct effect of the disease.

Urinary cystatin C: pediatric reference intervals and comparative assessment as a biomarker of renal injury among children in the regions with high burden of CKDu in Sri Lanka

BACKGROUND

Cystatin C (Cys-C) is an emerging biomarker of renal diseases and its clinical use, particularly for screening the communities affected by chronic kidney disease of unknown etiology (CKDu), is hindered due to the lack of reference intervals (RIs) for diverse ethnic and age groups. The present study aimed to define RIs for urinary Cys-C (uCys-C) for a healthy pediatric population in Sri Lanka and in turn compare the renal function of the residential children in CKDu endemic and non-endemic regions in Sri Lanka.

METHODS

A cross-sectional study was conducted with 850 healthy children (10-17 years) from selected locations for reference interval establishment, while a total of 892 children were recruited for the comparative study. Urine samples were collected and analyzed for Cys-C, creatinine (Cr) and albumin. Cr-adjusted uCys-C levels were partitioned by age, and RIs were determined with quantile regression (2.5th, 50th and 97.5th quantiles) at 90% confidence interval.

RESULTS

The range of median RIs for uCys-C in healthy children was 45.94-64.44 ng/mg Cr for boys and 53.58-69.97 ng/mg Cr for girls. The median (interquartile range) uCys-C levels of children in the CKDu endemic and non-endemic regions were 58.18 (21.8-141.9) and 58.31 (23.9-155.3) ng/mg Cr with no significant difference (P = 0.781). A significant variation of uCys-C was noted in the children across age.

CONCLUSIONS

Notably high uCys-C levels were observed in children with elevated proteinuria. Thus, uCys-C could be a potential biomarker in identifying communities at high risk of CKDu susceptibility.

Cystatin C relates to metabolism in healthy, pubertal adolescents

INTRODUCTION

The cystatin C (CysC) serum level is a marker of glomerular filtration rate and depends on age, gender, and pubertal stage. We hypothesize that CysC might overall reflect energy homeostasis and be regulated by components of the endocrine system and metabolites in pubertal adolescents.

METHODS

Serum CysC levels and further possible effector parameters in 5355 fasting, morning venous blood samples from 2035 healthy participants of the LIFE Child cohort study (age 8 to 18 years) were analyzed. Recruitment started in 2011, with probands followed up once a year. Linear univariate and stepwise multivariate regression analyses were performed.

RESULTS

Annual growth rate, serum levels of thyroid hormones, parathyroid hormone, insulin-like growth factor 1, hemoglobin A1c (HbA1c), uric acid, and alkaline phosphatase show relevant and significant associations with CysC serum concentrations (p <0.001). Furthermore, male probands' CysC correlated with the body mass index and testosterone among other sexual hormones. Multivariate analyses revealed that uric acid and HbA1c are associated variables of CysC independent from gender (p <0.001). In males, alkaline phosphatase (p <0.001) is additionally significantly associated with CysC. Thyroid hormones show significant correlations only in multivariate analyses in females (p <0.001).

CONCLUSIONS

The described associations strongly suggest an impact of children's metabolism on CysC serum levels. These alterations need to be considered in kidney diagnostics using CysC in adolescents. Additionally, further studies are needed on CysC in children.

Serum Cystatin C Levels Are Associated With Obesity in Adolescents Aged 14-17 Years

BACKGROUND

The association between serum cystatin C levels and obesity has not been fully explored in adolescents. This study aimed to explore the association between serum cystatin C levels and obesity in adolescents of different sexes.

METHODS

We conducted a cross-sectional study including 481 adolescents aged 14-17 years. Cystatin C level was measured by immunoassay. Health examinations data, biochemical parameters, and questionnaire information were collected. The restricted cubic spline model analyzed the association between cystatin C levels and obesity in boys and girls.

RESULTS

Boys exhibited significantly higher cystatin C levels than girls, with a mean level of 0.97 ± 0.10 mg/L in boys and 0.86 ± 0.09 mg/L in girls (P < 0.001). The restricted cubic spline model suggested that low or high cystatin C levels were associated with an increased risk of obesity in boys, whereas only higher cystatin C levels were associated with an increased risk of obesity in girls.

CONCLUSIONS

A U-shaped correlation was observed between serum cystatin C levels and the risk of obesity in boys. However, in girls, the risk of obesity showed a trend of initially increase and then decrease with increasing cystatin C levels. Longitudinal studies should be conducted to further investigate the diagnostic potential of cystatin C in the progression of early obesity in adolescents of different sexes.

Association Between the Concentration and Rangeability of Cystatin C and Mortality of COVID-19 Patients With or Without Type 2 Diabetes Mellitus: A Retrospective Analysis

BACKGROUND

We investigated if the concentration and "rangeability" of cystatin C (CysC) influenced the prognosis of coronavirus disease 2019 (COVID-19) in patients suffering from, or not suffering from, type 2 diabetes mellitus (T2DM).

METHODS

A total of 675 T2DM patients and 572 non-T2DM patients were divided into "low" and "high" CysC groups and low and high CysC-rangeability groups according to serum CysC level and range of change of CysC level, respectively. Demographic characteristics, clinical data, and laboratory results of the four groups were analyzed.

RESULTS

COVID-19 patients with a high level and rangeability of CysC had more organ damage and a higher risk of death compared with those with a low level or low rangeability of CysC. Patients with a higher level and rangeability of CysC had more blood lymphocytes and higher levels of C-reactive protein, alanine aminotransferase, and aspartate aminotransferase. After adjustment for possible confounders, multivariate analysis revealed that CysC >0.93 mg/dL was significantly associated with the risk of heart failure (OR = 2.231, 95% CI: 1.125-5.312) and all-cause death (2.694, 1.161-6.252). CysC rangeability >0 was significantly associated with all-cause death (OR = 4.217, 95% CI: 1.953-9.106). These associations were stronger in patients suffering from T2DM than in those not suffering from T2DM.

CONCLUSIONS

The level and rangeability of CysC may influence the prognosis of COVID-19. Special care and appropriate intervention should be undertaken in COVID-19 patients with an increased CysC level during hospitalization and follow-up, especially for those with T2DM.

Age appropriate reference intervals for eight kidney function and injury markers in infants, children and adolescents

Objectives

The use of kidney function and injury markers for early detection of drug-related glomerular or tubular kidney injury in infants, children and adolescents requires age-specific data on reference intervals in a pediatric healthy population. This study characterizes serum values for eight kidney function and injury markers in healthy infants, children and adolescents.

Methods

A single center prospective observational study was conducted between December 2018 and June 2019. Serum samples from 142 healthy infants, children and adolescents aged between 0 and ≤15 years were collected. Statistical analyses for eight markers (albumin (ALB), β2-microglobulin (B2M), β-trace protein (BTP), creatinine (SCR), cystatin C (CYSC), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), uromodulin (URO)) were performed to obtain reference intervals and associations with age, sex and weight were investigated (Pearson correlation, linear and piecewise regression).

Results

ALB and SCR increased with age (p<0.01), whereas B2M, BTP and KIM-1 values decreased with advancing age (p<0.05) in this healthy pediatric study population. CYSC showed dependency on sex (lower concentration in females) and decreased with age until reaching approximately 1.8 years; thereafter an increase with age was seen. NGAL and URO did not show any age-dependency.

Conclusions

This study provides age appropriate reference intervals for key serum kidney function and injury markers determined in healthy infants, children and adolescents. Such reference intervals facilitate the interpretation of changes in kidney function and injury markers in daily practice, and allow early detection of glomerular and tubular injury in infancy, childhood and adolescence.

Augmented renal clearance in pediatric intensive care: are we undertreating our sickest patients?

Many critically ill patients display a supraphysiological renal function with enhanced renal perfusion and glomerular hyperfiltration. This phenomenon described as augmented renal clearance (ARC) may result in enhanced drug elimination through renal excretion mechanisms. Augmented renal clearance seems to be triggered by systemic inflammation and therapeutic interventions in intensive care. There is growing evidence that ARC is not restricted to the adult intensive care population, but is also prevalent in critically ill children. Augmented renal clearance is often overlooked due to the lack of reliable methods to assess renal function in critically ill children. Standard equations to calculate glomerular filtration rate (GFR) are developed for patients who have a steady-state creatinine production and a stable renal function. Those formulas are not reliable in critically ill patients with acutely changing GFR and tend to underestimate true GFR in patients with ARC. Tools for real-time, continuous, and non-invasive measurement of fluctuating GFR are most needed to identify changes in kidney function during critical illness and therapeutic interventions. Such devices are currently being validated and hold a strong potential to become the standard of practice. In the meantime, urinary creatinine clearance is considered the most reliable method to detect ARC in critically ill patients. Augmented renal clearance is clearly associated with subtherapeutic antimicrobial concentrations and subsequent therapeutic failure. This warrants the need for adjusted dosing regimens to optimize pharmacokinetic and pharmacodynamic target attainment. This review aims to summarize current knowledge on ARC in critically ill children, to give insight into its possible pathophysiological mechanism, to evaluate screening methods for ARC in the pediatric intensive care population, and to illustrate the effect of ARC on drug exposure, therapeutic efficacy, and clinical outcome.

Can childhood obesity influence later chronic kidney disease?

Childhood overweight and obesity affects more and more children. Whilst associations of childhood overweight with later outcomes such as hypertension, diabetes and cardiovascular disease have been well documented, less is known about the association of childhood overweight and obesity with kidney disease. We review the existing evidence for the association of childhood obesity with markers of childhood and adult kidney disease. Whilst there is some evidence for an association, studies have not been able to distinguish between childhood being a sensitive time to develop later kidney problems, or whether observed associations of childhood obesity with poor outcomes are driven by greater lifelong exposure to obesity.

Cystatin C serum levels in healthy children are related to age, gender, and pubertal stage

BACKGROUND

This study aims to establish age- and gender-specific cystatin C (CysC) reference values for healthy infants, children, and adolescents and to relate them to pubertal stage, height, weight, and body mass index (BMI).

METHODS

Serum CysC and creatinine levels of 6217 fasting, morning venous blood samples from 2803 healthy participants of the LIFE Child study (age 3 months to 18 years) were analyzed by an immunoassay. Recruitment started in 2011; 1636 participants provided at least one follow-up measurement. Percentiles for CysC were calculated. Age- and gender-related effects of height, weight, BMI, and puberty status were assessed through linear regression models.

RESULTS

Over the first 2 years of life, median CysC levels decrease depending on height (ß = - 0.010 mg/l/cm, p < 0.001) and weight (ß = - 0.033 mg/l/kg, p < 0.001) from 1.06 to 0.88 mg/l for males and from 1.04 to 0.87 mg/l for females. Following the second year of age, the levels remain stable for eight years. From 11 to 14 years of age, there is an increase of median CysC levels in males to 0.98 mg/l and a decrease in females to 0.86 mg/l. The change is associated with puberty (ß = 0.105 mg/l/Tanner stage, p < 0.001 in males and ß = - 0.093 mg/l/Tanner stage, p < 0.01 in females) and in males with height (ß = 0.003 mg/l/cm, p < 0.001).

CONCLUSIONS

CysC levels depend on age, gender, and height, especially during infancy and puberty. We recommend the use of age- and gender-specific reference values for CysC serum levels for estimating kidney function in clinical practice.

Pediatric Inflammatory Bowel Diseases: Should We Be Looking for Kidney Abnormalities?

BACKGROUND

Kidney disease has been reported in adults with inflammatory bowel disease (IBD) and is regarded an extraintestinal manifestation or more rarely a side effect of the medical treatment.

METHODS

In this cross-sectional study we describe the extent of kidney pathology in a cohort of 56 children with IBD. Blood and urine samples were analyzed for markers of kidney disease and ultrasonography was performed to evaluate pole-to-pole kidney length.

RESULTS

We found that 25% of the patients had either previously reported kidney disease or ultrasonographic signs of chronic kidney disease. The median kidney size compared with normal children was significantly reduced. In a multivariate linear mixed model, small kidneys significantly correlated with the use of infliximab, whereas the use of enteral nutritional therapy was associated with larger kidneys.

CONCLUSION

Children with IBD are at risk of chronic kidney disease, and the risk seems to be increased with the severity of the disease.

Serum cystatin C in youth with diabetes: The SEARCH for diabetes in youth study

AIMS

We compared cystatin C in youth with versus without diabetes and determined factors associated with cystatin C in youth with type 1 diabetes (T1D) and type 2 diabetes (T2D).

METHODS

Youth (ages 12-19years) without diabetes (N=544) were ascertained from the NHANES Study 2000-2002 and those with T1D (N=977) and T2D (N=168) from the SEARCH for Diabetes in Youth Study. Adjusted means of cystatin C concentrations were compared amongst the 3 groups. Next, we performed multivariable analyses within the T1D and T2D SEARCH samples to determine the association between cystatin C and race, sex, age, diabetes duration, HbA1c, fasting glucose, and BMI.

RESULTS

Adjusted cystatin C concentrations were statistically higher in NHANES (0.85mg/L) than in either the T1D (0.75mg/L) or T2D (0.70mg/L) SEARCH groups (P<0.0001). Fasting glucose was inversely related to cystatin C only in T1D (P<0.001) and BMI positively associated only in T2D (P<0.01) while HbA1c was inversely associated in both groups.

CONCLUSIONS

Cystatin C concentrations are statistically higher in youth without diabetes compared to T1D or T2D, however the clinical relevance of this difference is quite small, especially in T1D. In youth with diabetes, cystatin C varies with BMI and acute and chronic glycemic control, however their effects may be different according to diabetes type.

Female Adolescents with Chronic or End-Stage Kidney Disease and Strategies for their Care

The prevalence of chronic or end-stage kidney disease in pediatric girls is lower than in boys, however, girls have unique morbidities that can have great effect on their quality of life. For female adolescents, creatinine excretion peaks at approximately 14 years of age and is significantly less than males, owing to lower muscle mass. Females have higher nitric oxide activity, and estrogens may contribute to lower blood pressure. Females excrete less growth hormone during the prepubertal and pubertal years. Females between the ages of 8 and 10 years show increased levels of parathyroid hormone and vitamin D, however, female adolescents with chronic kidney disease have less estrogen and loss of the luteinizing hormone pulsatile pattern. These biological, hormonal, and physical changes affect the psychosocial aspects of female adolescents with chronic kidney disease/end-stage kidney disease, and they must learn to manage their health to achieve good outcomes. Patients and their parents must learn disease management through a customized health care transition preparation in both the pediatric- and adult-focused settings. Clinical strategies are suggested for the care of these special patients.