|Year : 2015 | Volume
| Issue : 4 | Page : 712-717
|Serum cystatin-C and BETA 2-microglobulin as accurate markers in the early diagnosis of kidney injury in neonates: A single center study
Mohamed S El-Frargy1, Ahmed M El-Refaey2, Riham Eid2, Mokhtar A Hussien2
1 Department of Pediatric, Faculty of Medicine, Tanta University, Tanta, Egypt
2 Pediatric Nephrology Unit, Mansoura University Children's Hospital, Mansoura University, Mansoura, Egypt
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|Date of Web Publication||8-Jul-2015|
| Abstract|| |
Early detection of kidney injury in neonates is very important for appropriate management and prevention of serious complications; however, commonly used detectors as creatinine and blood urea nitrogen (BUN) do not directly reflect early renal cell injury. Serum cystatin-C (Cys-C) and beta 2-microglobulin (Β2M), serum creatinine and BUN were assessed in 20 neonates who developed renal impairment after admission to the neonatal intensive care unit and 10 healthy neonates. The means of serum Cys-C, Β2M and creatinine on Day 1 of admission in the cases and control groups were 2.15 ± 0.52 vs 0.45 ± 0.19, 7.18 ± 2.36 vs 1.92 ± 0.41 and 0.81 ± 0.07 vs 0.53 ± 0.20, respectively, with P-value <0.05 in only Cys-C and Β2M. We conclude that serum Cys-C and Β2M are suggested as simple and accurate markers for the early diagnosis of kidney injury in neonates than serum creatinine.
|How to cite this article:|
El-Frargy MS, El-Refaey AM, Eid R, Hussien MA. Serum cystatin-C and BETA 2-microglobulin as accurate markers in the early diagnosis of kidney injury in neonates: A single center study. Saudi J Kidney Dis Transpl 2015;26:712-7
|How to cite this URL:|
El-Frargy MS, El-Refaey AM, Eid R, Hussien MA. Serum cystatin-C and BETA 2-microglobulin as accurate markers in the early diagnosis of kidney injury in neonates: A single center study. Saudi J Kidney Dis Transpl [serial online] 2015 [cited 2020 Jan 24];26:712-7. Available from: http://www.sjkdt.org/text.asp?2015/26/4/712/160151
| Introduction|| |
Kidney injury in neonates is a frequent clinical problem, particularly in neonatal sepsis and hypoxia, which results in the inability of the kidneys to excrete wastes, concentrate urine, conserve electrolytes and maintain fluid balance.  Early diagnosis of kidney injury in neonates is essential for therapeutic decisions and prevention of long-term consequences. The current, most widely used biomarkers for the diagnosis of acute kidney injury include serum creatinine and blood urea nitrogen (BUN), which are not optimal, and tend to focus attention on later stages of kidney injury when therapies may be less effective. ,,
Cystatin-C (Cys-C) and Β2-microglobulin (Β2M) are low-molecular weight proteins produced by all nucleated cells at a constant rate. They are freely filtered by the glomeruli and reabsorbed and catabolized by proximal renal tubular cells. Therefore, their serum values could be better and early markers of neonatal kidney injury than serum creatinine level. ,,,
We aimed in this study to investigate the role of serum Cys-C and B2M in detecting early kidney injury in neonates to help in early and accurate diagnosis and intervention.
| Patients and Methods|| |
This prospective, case-control study was carried out at the Pediatrics and Clinical Pathology Departments, Tanta University Hospital, Egypt from October 2011 to October 2012. We studied 20 neonates admitted to the neonate intensive care unit (NICU) suffering from critical illness and developed renal impairment later as proven by BUN and serum creatinine. We excluded from the study patients with maternal abnormal renal function and renal disease and those who did not develop renal impairment or died during the study. We also studied 10 children ageand sexmatched healthy volunteer subjects serving as the control group during their regular neonatal checkup.
Informed consents were obtained from all the parents of the participants in the study and approval was obtained from the Tanta medical ethics committee.
Detailed clinical data including medical history and clinical examination were obtained on each patient, and the laboratory investigations included serum creatinine and BUN, serum Cys-C and B2M assayed by the enzymelinked immunosorbant assay (ELISA) technique.
In the BioVendor human Cys-C ELISA, standards, quality controls and samples were incubated in microtitrate plate wells pre-coated with polyclonal anti-human Cys-C antibody. After 30 min of incubation and washing, polyclonal anti-human Cys-C antibody, conjugated with horseradish peroxidase (HRP), was added to the wells and incubated for 30 min with the captured Cys-C. Following another washing step, the remaining HRP conjugate was allowed to react with the substrate solution (TMB). The reaction was finished with the addition of acidic solution and the absorbance of the resulting yellow product was measured spectrophotometrically at 450 nm; the absorbance was proportional to the concentration of Cys-C. A standard curve was constructed by plotting the absorbance values against the concentrations of Cys-C standards, and concentrations of the unknown samples.
Highly purified anti-human-B2M antibodies were bound to microwells. B2M, if present in diluted serum, plasma or urine, would bind to the respective antibodies. Washing of the microwells removed unspecific components. HRP conjugate anti-human B2M immunologically detected the bound B2M, forming a conjugate/B2M/antibody complex. Washing of the microwells removed the unbound conjugates. An enzyme substrate in the presence of bound conjugate hydrolyzed to form a blue color. The addition of an acid finished the reaction, forming a yellow end-product. The intensity of this yellow color was measured photometrically at 450 nm. The amount of color was directly proportional to the concentration of B2M present in the original samples. 
| Results|| |
The newborns included in the study were 18 males and 12 females. There were no significant differences between the two groups (study and contols) regarding the gender and the mode of delivery, as shown in [Table 1].
The mean and standard deviation of the gestational age (weeks), birth weight (g), Apgar score at 1 min, Apgar score at 5 min and hematocrit value (%) of the study patients and controls are presented in [Table 2]. There were no significant differences in the demographic characteristics, except Apgar score and hematocrit value (%), P <0.05.
The means of serum Cys-C, B2M and creatinine on Day 1 of admission are presented in [Table 3], which shows significant differences between the study patients and the controls regarding Cys-C and B2M and an insignificant difference regarding serum creatinine.
|Table 3: Means of serum cystatin-C (Cys-C), Beta-2 microglobulin (B2M) and creatinine on day 1 of admission.|
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[Table 4] shows the means of serum Cys-C, B2M and creatinine on Day 3 of admission. There were significant differences between the study patients and the controls regarding Cys-C, B2M and serum creatinine.
|Table 4: Mean of serum cystatin-C, beta-2 microglobulin and creatinine on day 3 of admission among the study groups.|
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A significant positive correlation between CysC and B2M was found, as shown in [Figure 1]. Sensitivity, specificity, predictive values and cut-off values of serum Cys-C, B2M and creatinine are presented in [Table 5], which shows that serum B2M was more sensitive than serum Cys-C, which was in turn more sensitive than serum creatinine in detecting renal function in the study patients. [Figure 2] shows the receiver-operating curve (ROC) for serum Cys-C, B2M and creatinine.
|Figure 1: Correlation between cystatin-C and beta-2 microglobulin (B2M) among the study groups.|
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|Figure 2: Receiver–operating curve (ROC) for serum cystatin-C, beta-2 microglobulin (B2M) and creatinine.|
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|Table 5: Sensitivity, specificity, predictive values and cut-off values of serum cystatin-C, beta-2 microglobulin (B2M) and creatinine.|
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| Discussion|| |
Kidney injury in neonates is characterized by a reversible increase in the blood concentration of creatinine and nitrogenous waste products and by the inability of the kidney to regulate fluid and electrolyte homeostasis appropriately. ,
Traditionally used markers such as BUN and creatinine are insensitive and non-specific, and do not adequately differentiate between the different stages of acute kidney injury. A delay in diagnosis prevents timely patient management decisions, including administration of therapeutic agents. Early biomarkers of acute kidney injury such as Cys-C and B2M facilitate earlier diagnosis and specific preventative and therapeutic strategies, ultimately resulting in fewer complications and improved outcomes. ,
In our study, we measured serum Cys-C, B2M and creatinine in neonates during the first 24 h of admission to NICU (Day 1) and during the third day of admission (Day 3).
During the first 24 h of admission, serum Cys-C increased in cases and remained within normal values in controls. These results were in agreement with other studies. ,, The same findings were observed with the serum B2M levels in our study as those with Cys-C, as found by others. ,, Sarkar et al demonstrated that serum creatinine was an insensitive and unreliable marker for the detection of mild to moderate acute kidney injury. Furthermore, Laterza et al,  LeBricon et al,  Bianchi et al  and John et al  found that serum Cys-C and B2M were simple and sensitive and useful markers better than serum creatinine to detect early acute kidney injury.
In our study, serum Cys-C remained elevated in the study patients on Day 3 after admission, as shown by other investigators who demonstrated continued superiority of serum Cys-C and serum B2M compared with serum creatinine in detecting early acute kidneyinjury ,,,,,,,,.
We conclude that from our study we suggest that Cys-C and B2M are easily measured in neonates and can be considered as simple, accurate and early markers of renal function impairment in this population.
Conflict of interest: None declared.
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Ahmed M El-Refaey
Pediatric Nephrology Unit, Mansoura University Children's Hospital, Mansoura University, Mansoura
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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