The clinical significance of serum cystatin C in critically ill newborns with normal serum creatinine

Age- and sex-specific reference intervals for the serum cystatin C/creatinine ratio in healthy children (0-18 years old)

Objective

This study aimed to investigate serum levels of the cystatin C (CysC)/creatinine (Cr) ratio and renal serum markers (CysC, Cr, urea, and uric acid [UA]) for different ages and by sex. We also aimed to establish pediatric reference intervals for the serum CysC/Cr ratio.

Methods

Serum samples were collected from 4765 healthy children (0–18 years old). Serum markers of renal function were measured, and the CysC/Cr ratio of each participant was calculated and statistically analyzed.

Results

The renal marker CysC did not substantially change after 1 year old. Cr, urea, and UA levels generally increased with age. However, the serum CysC/Cr ratio steadily decreased with age. The CysC/Cr ratio showed significant differences in age among all age groups and varied with sex, except for in the 1 to 6-year-old groups. The overall serum CysC/Cr ratio in girls was higher than that in boys.

Conclusion

Reference intervals of the serum CysC/Cr ratio in the pediatric population were established. These intervals need to be partitioned by age and sex.

Increased urinary neutrophil gelatinase-associated lipocalin in very-low-birth-weight infants with oliguria and normal serum creatinine

BACKGROUND

In infants, oliguria is defined as a urine output of <1.5 mL/kg/h. The aim of our study was to assess the impact of oliguria on urinary neutrophil gelatinase-associated lipocalin (NGAL) and serum cystatin C (CysC) levels in very-low-birth-weight infants (VLBWIs) with a normal serum creatinine (Cr) level.

METHODS

Fifty-seven VLBWIs were enrolled in the study. Urinary NGAL, serum CysC and Cr levels and urinary NGAL/Cr ratios were measured. Infants with Apgar scores of >5 at 5 min and/or a serum Cr level of >1.5 mg/dL or those treated for patent ductus arteriosus were excluded. In case of antibiotic treatment, blood and urine samples were collected at ≥48 h after discontinuation of antibiotic treatment.

RESULTS

There was a significant difference in gestational age between infants with oliguric episodes during hospitalization and those without, but not in birth weight, perinatal or postnatal factors. Gestational age was negatively correlated with urinary NGAL and serum CysC levels and urinary NGAL/Cr ratio (p < 0.05), whereas postnatal age was negatively correlated with serum Cr level and urinary NGAL/Cr ratio (p < 0.05). Of the 117 urine and blood samples collected, 25 (21.4%) were obtained from neonates with oliguric episodes. After adjusting for gestational age and postnatal age, comparison of samples collected in infants with and without oliguric episodes revealed significant differences in the mean level of urinary NGAL and in the urinary NGAL/Cr ratio, but not in mean serum CysC or serum Cr levels. The urinary NGAL level [area under the curve (AUC) 0.886, 95% confidence interval (CI) 0.814-0.937] and urinary NGAL/Cr ratio (AUC 0.853, 95% CI 0.775-0.911) showed significantly greater discrimination for oliguria than serum CysC (AUC 0.610, 95% CI: 0.515-0.699) or serum Cr (AUC 0.747, 95%CI 0.659-0.823) levels.

CONCLUSIONS

Urinary NGAL level and urinary NGAL/Cr ratio were more sensitive markers for the presence of oliguria in VLBWIs with normal serum Cr levels than serum CysC level.

Serum cystatin c is not superior to serum creatinine for early diagnosis of contrast-induced nephropathy in patients who underwent angiography

BACKGROUND

Iodiated contrast-induced nephropathy (CIN) is a serious complication of contrast-enhanced imaging. The aim of this study was to evaluate the diagnostic sensitivities and specificities of serum cystatin C (sCys C) and serum creatinine (sCr) for CIN and to further investigate difference of the incidence, risk factors, and in-hospital and 3-month prognosis of CIN according to sCys C criteria and sCr criteria.

METHODS

We prospectively evaluated 213 patients who underwent angiography. The sCr and sCys C concentrations were detected before and at 48 hours, 72 hours after the procedure. The incidence, risk factors, and in-hospital and 3-month prognosis of CIN were analyzed. Receiver operating characteristic curve (ROC) analysis was performed for sCr and sCys C 48 hours after procedure.

RESULTS

The incidence of CIN was 24.4% (sCys C criteria) and 8% (sCr criteria). Diabetes mellitus, dehydration, and hypoalbuminemia were independent risk factors for CIN. Area under the ROC of sCys C 48 hours after procedure was not superior to sCr (0.715 vs 0.790, P=.178). The mortality of patients with CIN in sCr criteria increased significantly (P<.05).

CONCLUSION

In this study, the incidence and risk factors of CIN were related to diagnostic criteria. The sCys C was not superior to sCr for predicting CIN in the patients who underwent angiography.

Longitudinal analysis of serum cystatin C for estimating the glomerular filtration rate in preterm infants

BACKGROUND

Cystatin C (Cys-C) is a more sensitive marker of renal function than creatinine (Cre) in pediatric and adult populations. However, the reference values of serum Cys-C for estimating glomerular filtration rates (eGFRs) in premature infants during the first year of life have not been sufficiently studied.

METHODS

In this prospective study, 481 blood samples were collected from 261 preterm infants with uncomplicated clinical courses during their first year of life. Infants were divided into three groups according to gestational age at birth: 27-30 weeks, 31-33 weeks, and 34-36 weeks. Serum Cys-C and Cre levels were measured at 6-30 days, 3-5 months, 7-9 months, and 12-14 months after birth and the eGFR was calculated using two previously published equations.

RESULTS

The median serum Cys-C levels were 1.776, 1.248, 1.037, and 0.960 mg/L at the first, second, third, and fourth measurement time-point, respectively, with the value significantly decreasing with age up to 12-14 months. Cys-C levels were independent of gestational age and gender. In contrast to Cys-C, serum Cre values declined rapidly up to 3-5 months, then remained constant up to 12-14 months. Using the Cys-C-based equation, the eGFR significantly increased with increasing age until approximately 1 year after birth; however, no such trend was noted using the equation based on Cys-C + Cre.

CONCLUSIONS

Reference ranges for Cys-C in premature infants decline gradually over the first year after birth. Cys-C appears to be a more reliable marker than Cre for estimating GFR in preterm infants.

Prediction of urine volume soon after birth using serum cystatin C

BACKGROUND

Urine volume is an important clinical finding particularly during the early neonatal period. Oliguria is not a sign of impaired renal function but also a predictive factor for various complications and prognoses. It has been postulated that serum cystatin C (S-CysC) is a more sensitive biomarker for renal function than serum creatinine (S-Cr) in both adults and children. The objective of the current study was to investigate whether urine volume during 24 h after birth can be predicted using S-CysC.

METHODS

The subjects were 87 infants. The average gestational age was 34.7 ± 2.9 weeks and the average birth weight was 2135 ± 614 g. Blood samples were obtained from either the umbilical cord or the peripheral veins or artery of the newborn at birth. Data regarding the amount of urine volume and fluid intake during the first 24 h of life, maternal S-Cr and S-CysC levels within 48 h before delivery, and neonatal S-Cr and S-CysC levels at birth were collected from the medical records.

RESULTS

A significantly positive correlation was observed between maternal and neonatal S-Cr levels (r = 0.84, p < 0.0001) but not between maternal S-Cr levels and neonatal S-CysC levels (r = -0.069, p = 0.52). A significant negative correlation was seen between neonatal S-CysC levels and urine volume (r = -0.47, p < 0.0001).

CONCLUSION

The present study findings indicate that it may be possible to use S-CysC levels at birth to predict urine volume during the first 24 h of life.

Reference intervals of serum cystatin C/creatinine ratio of 30 postnatal days in neonates

BACKGROUND

A number of recent reports have suggested that the cystatin C/creatinine (CysC/Cr) ratio might be a useful biomarker of renal function in pediatric patients. In this study we investigated the reference intervals of the serum CysC/Cr ratio for neonates including very low birth weight infants.

CASE-DIAGNOSIS/TREATMENT

A total of 883 blood samples were collected from 246 neonates during the first 30 days of life for the concurrent measurement of serum CysC and Cr levels. Infants with symptoms or signs of acute kidney injury, systemic illness, congenital anomaly, or renal pathology were excluded. The association between serum CysC/Cr ratio and the subgroups of patients was also analyzed. Reference intervals of serum CysC/Cr ratio were determined according to the postnatal age and post-conceptional age (PCA). CysC/Cr ratio level increased according to PCA, except in the first three postnatal days. The serum CysC/Cr ratio correlated positively with gestational age at birth, birth weight, postnatal age, and PCA, and negatively with serum CysC and Cr (P < 0.001).

CONCLUSIONS

Reference levels of serum CysC/Cr ratio were determined according to postnatal age and PCA. As the serum CysC/Cr ratio is dependent on several clinical parameters, these should be considered when assessing the serum CysC/Cr ratio in neonates.

Reference values of serum cystatin C in very low-birthweight premature infants

AIM

To determine reference values for cystatin C (CysC) and its correlation with creatinine (Cr), gestational age, birthweight and maternal Cr status in very low-birthweight (VLBW) preterm infants.

METHOD

The study included 113 VLBW premature infants (<1500 g) of ≤ 32 gestational week. Serum Cr and CysC of the infant and serum Cr of the mother were analysed.

RESULTS

The mean level of CysC was 1.77 ± 0.38 mg/L on day 1 and 1.61 ± 0.37 mg/L on day 3, and the decrease was statistically significant. There was a significant correlation only between maternal Cr and first-day Cr values and negative correlations between Cr and gestational age and birthweight on third day. Creatinine was not correlated with CysC both on day 1 (r = -0.077, p = 0.417) and day 3 (r = 0.132, p = 0.164).

CONCLUSION

Here, we report the reference ranges for CysC and Cr on first and third day in VLBW infants. CysC concentrations significantly decrease by day 3 compared with day 1 and are independent of gestational week, birthweight and maternal renal function status in VLBW preterm infants.