Comparing cystatin C and creatinine in the diagnosis of pediatric acute renal allograft dysfunction

Optimal Glomerular Filtration Rate Equations for Various Age Groups, Disease Conditions and Ethnicities in Asia: A Systematic Review

(1) Background: The performance of estimated glomerular filtration rate (eGFR) equations in the Asian population has been widely questioned. The primary objective of this study was to gather evidence regarding optimal GFR equations in Asia for various age groups, disease conditions, and ethnicities. The secondary objective was to see whether the equations based on the combination of creatinine and cystatin C biomarkers if employed are satisfactory across different age groups and disease conditions in various ethnicities in Asia compared to those based on either of the single biomarkers. (2) Methods: Validation studies that had both creatinine and cystatin C-based equations either alone or in combination, validated in specific disease conditions, and those which compared the performance of these equations with exogenous markers were eligible only. The bias, precision, and 30% accuracy (P30) of each equation were recorded accordingly. (3) Results: Twenty-one studies consisting of 11,371 participants were included and 54 equations were extracted. The bias, precision, and P30 accuracies of the equations ranged from -14.54 to 9.96 mL/min/1.73 m2, 1.61 to 59.85 mL/min/1.73 m2, and 4.7% to 96.10%. The highest values of P30 accuracies were found for the JSN-CKDI equation (96.10%) in Chinese adult renal transplant recipients, for the BIS-2 equation (94.5%) in Chinese elderly CKD patients, and Filler equation (93.70%) also in Chinese adult renal transplant recipients. (4) Conclusions: Optimal equations were identified accordingly and it was proven that combination biomarker equations are more precise and accurate in most of the age groups and disease conditions. These can be considered equations of choice for the specific age groups, disease conditions, and ethnicities within Asia.

Assessment of Kidney Function in Children

A good understanding of kidney function tests is essential for patient care. Urinalysis is the commonest used test for screening purposes in ambulatory settings. Glomerular function is assessed further by urine protein excretion and estimated glomerular filtration rate and tubular function by various tests such as urine anion gap and excretion of sodium, calcium, and phosphate. In addition, kidney biopsy and/or genetic analyses may be required to further characterize the underlying kidney disease. In this article, we discuss maturation and the assessment of kidney function in children.

Levamisole causes a transient increase in plasma creatinine levels but does not affect kidney function based on cystatin C

BACKGROUND

In pediatric patients treated with levamisole to prevent relapses of idiopathic nephrotic syndrome (INS), a transient and non-progressive rise in creatinine levels has been observed. It has been suggested that levamisole affects tubular secretion of creatinine. However, other potential mechanisms - nephrotoxicity and interference with the analytical assay for creatinine - have never been thoroughly investigated.

METHODS

In three steroid-sensitive nephrotic syndrome (SSNS) patients with elevated plasma creatinine levels, treated with levamisole 2.5 mg/kg every other day, serum cystatin C was determined. The glomerular filtration rate (GFR) was estimated using the full age spectrum for creatinine and the full age spectrum for cystatin C equations. Interference of levamisole with the enzymatic creatinine assay was tested using spare human plasma of different creatinine concentrations spiked with levamisole (4, 20, and 100 µM).

RESULTS

Three patients who received levamisole with elevated plasma creatinine levels had normal serum cystatin C levels and corresponding estimated GFR. There was no assay interference.

CONCLUSION

Levamisole increases plasma creatinine levels, which is most probably due to impaired tubular secretion of creatinine since there was no assay interference and patients had normal eGFR based on serum cystatin C. However, interference of metabolites of levamisole could not be excluded. To monitor GFR, cystatin C in addition to creatinine should be used and be measured before and during levamisole use.

Association of cystatin C with coronary artery calcification in patients undergoing multidetector computed tomography

Cystatin C is associated with atherosclerosis, but the relationship between cystatin C and coronary artery calcification (CAC) is uncertain. The purpose of this study was to evaluate the predictive value of cystatin C on the occurrence and severity of CAC.A total of 1447 hospitalized patients with coronary computed tomography angiography were selected in this study. According to the CAC score (CACS), patients were divided into calcification group (with CAC, n = 749) and control group (without CAC, n = 698). The calcification group was further divided into low calcification group (CACS < 100, n = 407), medium calcification group (CACS 100-400, n = 203), and high calcification group (CACS≥400, n = 139).Patients with CAC had higher cystatin C level than those in control group (P < .05). With the increase of calcification score, the cystatin C level showed an upward trend. The cystatin C level in the high calcification group was significantly higher than those in the low and medium calcification group (P < .05). ROC curve analysis showed that cystatin C had a high predictive value for the occurrence of CAC [area under the curve 0.640, 95% confidence interval (95% CI) 0.591-0.690, cut-off value 0.945 mg/L, sensitivity 0.683, specificity 0.558, P < .05] and severe CAC (area under the curve 0.638, 95% CI 0.550-0.762, cut-off value 0.965 mg/L, sensitivity 0.865, specificity 0.398, P < .05). Multivariate logistic regression analysis showed that cystatin C was an independent predictor of severe CAC (AOR 3.748, 95% CI 1.138-10.044, P < .05).Cystatin C was significantly associated with the occurrence and severity of CAC, suggesting that cystatin C had the potential as a predictor of CAC.

Superiority of Cystatin C over Creatinine for Early Diagnosis of Acute Kidney Injury in Pediatric Acute Lymphoblastic Leukemia/Lymphoblastic Lymphoma

The exact incidence of acute kidney injury (AKI) during chemotherapy for acute lymphoblastic leukemia (ALL)/lymphoblastic lymphoma (LBL) is unknown. Furthermore, childhood cancer survivors are at risk of AKI-chronic kidney disease transition. Thus, early diagnosis of AKI is crucial. This study aimed to elucidate the incidence of AKI in patients undergoing chemotherapy for pediatric ALL/LBL and to compare the usefulness of serum cystatin C (CysC)- and creatinine (Cr)-based estimated glomerular filtration rate (eGFR) as diagnostic measures. Data of 16 patients with ALL/LBL treated with a total of 75 courses of chemotherapy were retrospectively analyzed. CysC- and Cr-based eGFR were measured before and three times per week during therapy. To calculate the eGFR, an equation for Japanese children was used. AKI was diagnosed when eGFR dropped by ≥ 25% from the highest eGFR value obtained during the latest 2 weeks since the start of chemotherapy. AKI was graded based on the pediatric Risk, Injury, Failure, Loss, End Stage Renal Disease scale. All patients developed AKI during chemotherapy; however, more than 90% of the cases were mild and eventually recovered. No significant differences were found in the incidence of AKI between CysC- and Cr-based eGFR (p = 0.104). The median time to AKI diagnosis was significantly shorter in the CysC-based eGFR than in the Cr-based eGFR (8 vs. 17 days, p < 0.001). In this study, all patients with pediatric ALL/LBL could develop mild AKI during treatment. CysC-based eGFR is a more effective measure than Cr-based eGFR for the early diagnosis of AKI.

Concordance between creatinine- and cystatin C-based eGFR in clinical practice

The mean of GFR-estimates based on serum creatinine (eGFR_crea) and cystatin C (eGFR_cys) has superior accuracy than each estimate alone. Recent studies have shown that agreement between eGFR_crea and eGFR_cys is an indicator for the accuracy of the mean of the two estimates. As long as the difference between the two (|ΔeGFR|) is below 40%, a high P₃₀ accuracy rate of more than 90% was documented in research settings using gold-standard GFR measurements. This was the case in approximately 80% of the measurements. The study was set out to explore |ΔeGFR| in a broader pediatric nephrological population and identify factors influencing the discrepancy between eGFR_crea and eGFR_cys. We retrospectively analyzed 1596 simultaneous cystatin C and creatinine measurements in 649 unique patients at the pediatric nephrology outpatient clinic of VU university medical center. The FASage equation was used to calculate eGFR_crea, FAScys for eGFR_cys. |ΔeGFR| was calculated as 100x(|eGFR_crea-eGFR_cys|)/(0.5x(eGFR_crea+eGFR_cys). ΔeGFR below 40% was considered high agreement. Patient characteristics like age, diagnosis, glucocorticosteroid use, eGFR, BMI and sex were analyzed for their effect on ΔeGFR below or above 40% using non-parametric tests and a potential explanation for measurements with low agreement was sought. Eighty-seven percent of the population had a |ΔeGFR| lower than 40%. Measurements with |ΔeGFR| above 40% were significantly more frequent from patients with neural tube defects. In 102 out of 208 measurements with low agreement, a potential explanation was found. In a broad pediatric nephrological population, |ΔeGFR| is below 40% in the vast majority of measurements. In this group, the mean of eGFR_crea and eGFR_cys can be used as an accurate estimate of GFR.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

Cystatin C: A Primer for Pharmacists

Pharmacists are at the forefront of dosing and monitoring medications eliminated by or toxic to the kidney. To evaluate the effectiveness and safety of these medications, accurate measurement of kidney function is paramount. The mainstay of kidney assessment for drug dosing and monitoring is serum creatinine (SCr)-based estimation equations. Yet, SCr has known limitations including its insensitivity to underlying changes in kidney function and the numerous non-kidney factors that are incompletely accounted for in equations to estimate glomerular filtration rate (eGFR). Serum cystatin C (cysC) is a biomarker that can serve as an adjunct or alternative to SCr to evaluate kidney function for drug dosing. Pharmacists must be educated about the strengths and limitations of cysC prior to applying it to medication management. Not all patient populations have been studied and some evaluations demonstrated large variations in the relationship between cysC and GFR. Use of eGFR equations incorporating cysC should be reserved for drug management in scenarios with demonstrated outcomes, including to improve pharmacodynamic target attainment for antibiotics or reduce drug toxicity. This article provides an overview of cysC, discusses evidence around its use in medication dosing and in special populations, and describes practical considerations for application and implementation.

The role of urinary NGAL and serum cystatin C in assessing the severity of ureteropelvic junction obstruction in infants

BACKGROUND

The ideal management of ureteropelvic junction obstruction (UPJO) remains debatable. This prospective case-control study aimed to investigate if urinary levels of Neutrophil Gelatinase-Associated Lipocalin (NGAL) and serum levels of cystatin C could distinguish surgical from non-surgical cases of UPJO and if they could detect earlier impairment of renal function.

METHODS

Biomarkers were measured in the following age-matched groups: (a) 22 infants with surgical UPJO, at initial diagnosis and 12 months postoperatively (groups A1 and A2, respectively); (b) 19 infants with non-surgical UPJO (group B); and (c) 17 controls (group C). Based on serum cystatin C levels, estimated glomerular filtration rate (eGFR) was calculated.

RESULTS

Urinary NGAL (uNGAL) was significantly higher in group A1 vs. group A2 (p = 0.02) and in group A1 vs. group C (p = 0.03), whereas there was no statistically significant difference between groups A2 and C (p = 0.77). Likewise, cystatin C levels were significantly higher in group A1 vs. group A2 and in group A1 vs. group C (p = 0.004 and p = 0.02, respectively), but no statistically significant difference between groups A2 and C (p = 0.82). uNGAL and serum cystatin C did not differ between groups B and A, nor did they differ between groups B and C. Cystatin C levels and eGFR of group A1 were significantly higher than those of group A2 and group C (p = 0.0001 and p = 0.02, respectively).

CONCLUSION

It seems that NGAL and cystatin C are able to distinguish patients who were treated surgically from healthy controls, and their levels appear to improve significantly following surgery.

The value of cystatin C and urinary and serum neutrophil gelatinase-associated lipocalin during the perioperative period of renal transplantation

Background

The perioperative management of renal transplantation is complex. Our research aimed to study the clinical value of cystatin-C (Cys-C) and urinary and serum neutrophil gelatinase-associated lipocalin (NGAL) during the perioperative period of renal transplantation.

Methods

We collected the clinical information of 47 renal transplantation patients. Urine and serum samples were collected daily until the second week and then weekly until discharge to determine serum NGAL (s-NGAL), urine NGAL (u-NGAL), serum creatinine (s-Cr), and Cys-C levels. Receiver-operating characteristic (ROC) analysis was used, and the area under the curve (AUC) was compared to evaluate the accuracy of the diagnosis of delayed graft function (DGF). Multivariable analysis was used to find the association between the markers and renal function at discharge.

Results

In our research, the value of Cys-C, serum NGAL, and urine NGAL were higher in DGF group. In the ROC analysis, Cys-C had the highest AUC (0.939) compared with s-NGAL (0.909), u-NGAL (0.856), and s-Cr (0.747). Multivariable analysis showed that Cys-C levels in the first week after the operation and cold ischemia time were independently associated with estimated glomerular filtration rate (eGFR) at discharge (P<0.05).

Conclusions

Our results showed that Cys-C, serum NGAL, and urine NGAL could reflect renal function sensitively. Cys-C had the highest sum of sensitivity and specificity at 4.77 mg/L, with a sensitivity of 0.818 and specificity of 0.889. The Cys-C level during the first week after the operation was independently associated with eGFR at discharge and could predict the short-term prognosis of renal transplantation patients.

Evaluation of cystatin C-derived glomerular filtration rate equations in Chinese population

ABTRACTGlomerular filtration rate (GFR) has become the best indicator for assessing renal function. This study aims to validate the existing cystatin C (CysC)-derived estimated glomerular filtration rate (eGFR) equations in Chinese patients to explore whether the reported CysC-derived eGFR formulas could be applied to the Chinese population. This study validated the equations in a population totaling 1816 inpatients. We calculated eGFR by different CysC-derived equations, then compared with the mGFR. Equation performance was assessed by bias (mean difference between mGFR and eGFR), precision (inter-quartile range of difference) and accuracy (mainly, accuracy within 30% [P₃₀]). All equations expressed poor performance in dialysis patients (n = 345), and the performance for non-dialysis patients (n = 1471) were significantly greater than that in dialysis patients. Feng and Pei equations had higher P₃₀ (50.82% and 49.73%, respectively) than the widely used CKD-EPI_CysC (41.10%) and MacIsaac equations (48.23%), and the distribution of eGFR values is more similar to the distribution of mGFR in non-dialysis patients. Similar trends showed in mGFR, sex, age, and BMI subgroups. However, no equation met the guideline standard of P₃₀ ≥ 75%. Our results suggest that the published CysC-based eGFR equations are not suitable for dialysis patients, and the accuracy of equations for non-dialysis patients significantly better than the dialysis ones. Moreover, Feng and Pei equation showed better performance in non-dialysis patients.

The diagnostic value of serum creatinine and cystatin c in evaluating glomerular filtration rate in patients with chronic kidney disease: a systematic literature review and meta-analysis

BACKGROUND

Serum biomarkers, such as serum creatinine (SCr) and serum cystatin C (SCysC), have been widely used to evaluate renal function in patients who have chronic kidney disease (CKD).

OBJECTIVE

This article aims to assess the value of determining SCr and SCysC levels in patients that have long-term kidney disease. Approaches: MEDLINE, EmBase, the Cochrane Library and other databases were searched using both MeSH terms and text words to collect research that assessed the diagnostic value of using SCr and SCysC to evaluate Glomerular Filtration Rate (GFR) in patients with CKD. Data were converted into fourfold tables. Summary Receiver Operating Characteristic Curves and meta-analyses were accomplished via Meta-Disc version 1.4.

RESULTS

In total, 21 relevant articles involving 3112 study subjects were included in our review. Results showed that the collective sensitivity for SCr and SCysC was 0.77 (95% CI: 0.69-0.84) and 0.87 (95% CI: 0.82-0.91), respectively. The pooled specificity for SCr and SCysC was 0.91 (95% CI: 0.86-0.94) and 0.87 (95% CI: 0.82-0.91), respectively. Subgroup analyses demonstrated that when GFR cut-off values are set to 60 (ml/min/1.73 m²), the pooled sensitivity is 0.94 (95% CI: 0.90-0.96) for SCysC and 0.75 (95% CI: 0.68-0.82) for SCr.

CONCLUSIONS

The diagnostical accuracy for impaired kidney function favors SCysC. Confidence intervals for the pooled sensitivity and specificity for SCr and SCysC overlap. However, SCysC is more sensitive for estimating GFR than SCr when GFR cut-off values are set to 60 (ml/min/1.73 m²).

Dexamethasone Modifies Cystatin C-Based Diagnosis of Acute Kidney Injury During Cisplatin-Based Chemotherapy

BACKGROUND/AIMS

Plasma cystatin C (pCysC) may be superior to serum creatinine (sCr) as a surrogate of GFR. However, the performance of pCysC for diagnosing acute kidney injury (AKI) after cisplatin-based chemotherapy is potentially affected by accompanying corticosteroid anti-emetic therapy and hydration.

METHODS

In a prospective observational study pCysC, sCr, urinary kidney injury molecule-1 (KIM-1), and urinary clusterin were measured over 2 weeks in 27 patients given first-cycle chemotherapy. The same variables were measured over 2 weeks in Sprague-Dawley rats given a single intraperitoneal injection of dexamethasone, cisplatin, or both, and in controls.

RESULTS

In patients, pCysC increases were greater than sCr 41% vs. 16%, mean paired difference 25% (95% CI: 16-34%)], relative increases were ≥ 50% in 9 patients (35%) for pCysC compared with 2 (8%) for sCr (p = 0.04) and increases in sCr were accompanied by increased KIM-1 and clusterin excretion, but increases in pCysC alone were not. In rats, dexamethasone administration produced dose-dependent increases in pCysC (and augmented cisplatin-induced increases in pCysC), but did not augment histological injury, increases in sCr, or KIM-1 and clusterin excretion.

CONCLUSIONS

In the presence of dexamethasone, elevation of pCysC does not reliably diagnose AKI after cisplatin-based chemotherapy.

Reference ranges for serum β-trace protein in neonates and children younger than 1 year of age

BACKGROUND

β-Trace protein (BTP) has been proposed as an alternative endogenous marker of glomerular filtration rate. Data on BTP reference ranges in young children are scarce. We therefore aim to establish reference ranges and examine the developmental course of serum BTP in basically healthy children younger than 1 year of age.

METHODS

Single blood samples were taken from healthy children (born at gestational age ≥37 weeks) <12 months of age. Serum BTP was measured using the N latex B-trace protein assay (Siemens Diagnostics, Deerfield, IL, USA) on an Immage® 800 Rate Nephelometer (Beckman Coulter Inc. Brea, CA, USA). Serum creatinine and cystatin C were additionally determined and compared to reference values to confirm a normal renal function.

RESULTS

From June 2010 to January 2014, 95 blood samples were collected from 95 children {67.4% male; median age 120 days [inter quartile range 57-166]}. BTP was normally distributed (mean concentration 0.84±standard deviation 0.35 mg/L). Considering all children, the 50th centile BTP reference concentration was 0.82 mg/L (5th-95th centiles; 0.27-1.38). BTP concentrations were the highest in neonates and steadily declined with increasing age (Spearman's rank correlation was -0.415, p=0.002). No gender differences were found.

CONCLUSIONS

Our data provide a BTP reference range for the first year of life. Seeing the biological pattern of BTP, with only a limited postnatal decline, this marker might offer a promising alternative to serum creatinine-based methods for estimating glomerular filtration rate in newborns.

Renal function in children and adolescents with Duchenne muscular dystrophy

Improved life expectancy and the need for robust tools to monitor renal safety of emerging new therapies have fueled the interest in renal function in Duchenne muscular dystrophy (DMD) patients. We aimed to establish a methodology to accurately assess their renal function. Twenty DMD patients (5-22 years) were included in this prospective study. After obtaining medical history, all patients underwent a clinical examination, 24-hour ambulatory blood pressure monitoring, ultrasound of the kidneys, direct GFR measurement ((51)Cr-EDTA, mGFR), complete blood and urine analysis. Seventeen of 20 patients were treated with corticosteroids and 5/20 with angiotensin converting enzyme inhibitor (lisinopril). No patient suffered from urinary tract infections or other renal diseases. Hypertension (systolic or diastolic blood pressure >P95) was found in 9/20 patients (8/9 patients were on steroid treatment) and a non-dipping blood pressure profile in 13/20 subjects (10/13 patients were on steroid treatment). Urinary protein to creatinine ratio was elevated in 17/18 patients, whereas 24-hour urine protein excretion was normal in all subjects. Median interquartile range (IQR) mGFR was 130.4 (29.1) mL/min/1.73 m(2). Hyperfiltration (mGFR >150 mL/min/1.73 m(2)) was found in 5/20 patients. Inverse correlation between mGFR and age was observed (R(2) = 0.45, p = 0.001). Serum creatinine based estimated GFR (eGFR) equations overestimated mGFR up to 300%. eGFR based on cystatin C Filler equation was closest to the mGFR (median eGFR (IQR) of 129.5 (39.7) mL/min/1.73 m(2)). Our study demonstrates a high prevalence of hyperfiltration and hypertension in children and adolescents with DMD. Because the majority of hypertensive patients were under corticosteroid treatment, the iatrogenic cause of hypertension cannot be excluded. Serum or urine creatinine measurements are of no value to evaluate renal function in DMD patients due to the reduced skeletal muscle mass.

A meta-analysis on diagnostic value of serum cystatin C and creatinine for the evaluation of glomerular filtration function in renal transplant patients

OBJECTIVES

This meta-analysis aimed to perform a systematic review on comparing the diagnostic value of serum cystatin C and creatinine for glomerular filtration rate in renal transplant patients.

METHODS

The data was extracted into 2×2 table after the articles were assessed by the tool of QUADAS and heterogeneity analysis. The SROC curve and meta-analysis were performed by MetaDisc1.4.

RESULTS

Meta-analysis showed that the serum cystatin C had no heterogeneity (P=0.418, I2=2.2%, DOR=25.03), while creatinine heterogeneity was high (P=0.109, I2=37.5%, DOR=9.11). The values of SEN, SPE and SAUC were calculated as 0.86, 0.70 and 0.9015 for cystatin C, and 0.78, 0.73 and 0.8285 for creatinine individually. This study utilized GFR detection and subgroups analysis by cutoff. The PLR was 6.13 and the NLR was 0.12 for cystatin C, compared to SCr (3.72, 0.32). There was homogeneity among these studies using PENIA testing for cystatin C (χ2=2.61, P=0.4560, I2=0.0%.

CONCLUSIONS

There were significant correlations among cystatin C , creatinine and glomerular filtration rate (GFR). Cystatin C had more sensitivity but less specificity than creatinine for evaluation of GFR. Cystatin C had strong ability in diagnosing renal function after renal transplant and ruling out diagnostic efficacy.

Serum cystatin C is a poor biomarker for diagnosing acute kidney injury in critically-ill children

Background:

Accurate diagnosis of acute kidney injury (AKI) is problematic especially in critically-ill patients in whom renal function is in an unsteady state.

Aim:

Our aim was to evaluate the role of serum (S.) cystatin C as an early biomarker of AKI in critically-ill children.

Subjects and Methods:

S. creatinine and S. cystatin C were measured in 32 critically-ill children who were at risk for developing AKI. AKI was defined by both: Risk,-injury,-failure,-loss, and-endstage renal disease (RIFLE) classification and glomerular filtration rate (GFR) <80 ml/min/1.73 m². GFR was estimated by both Schwartz formula and S. cystatin C-based equation.

Results:

S. cystatin C was not statistically higher in AKI patients compared with non-AKI by RIFLE classification (median 1.48 mg/l vs. 1.16 mg/l, P = 0.1) while S. creatinine was significantly higher (median 0.8 mg/dl vs. 0.4 mg/dl, P = 0.001). On estimating GFR by the two equations we found, a lag between rise of S. cystatin C and creatinine denoted by lower GFR by Schwartz formula in four patients, on other hand, six patients had elevated S. cystatin C with low GFR despite normal creatinine and GFR, denoting poor concordance between the two equations and the two markers. The ability of S. creatinine in predicting AKI was superior to S. cystatin with area under the curve (AUC) 0.95 with sensitivity and specificity (100% and 84.6%, respectively) using the RIFLE classification. The same findings were found when using Schwartz formula.

Conclusion:

S. cystatin C is a poor biomarker for diagnosing AKI in critically-ill children.

Multicenter study of creatinine- and/or cystatin C-based equations for estimation of glomerular filtration rates in Chinese patients with chronic kidney disease

Objective

To establish equations for the estimation of glomerular filtration rates (eGFRs) based on serum creatinine (SCr) and/or serum cystatin C (SCysC) in Chinese patients with chronic kidney disease (CKD), and to compare the new equations with both the reference GFR (rGFR) and the literature equations to evaluate their applicability.

Methods

The 788 Chinese CKD patients were randomly divided into two groups, the training group and the testing group, to establish new eGFR-formulas based on serum CysC and to validate the established formulas, respectively. ^99mTc-DTPA clearance (as the rGFR), serum Cr, and serum CysC were determined for all patients, and GFR was calculated using the Cockcroft-Gault equation (eGFR1), the MDRD formula (eGFR2), the CKD-EPI formulas (eGFR3, eGFR4), and the Chinese eGFR Investigation Collaboration formulas (eGFR5, eGFR6). The accuracy of each eGFR was compared with the rGFR.

Results

The training and testing groups' mean GFRs were 50.84±31.36 mL/min/1.73 m² and 54.16±29.45 mL/min/1.73 m², respectively. The two newly developed eGFR formulas were fitted using iterative computation: and . Significant correlation was observed between each eGFR and the rGFR. However, proportional errors and constant errors were observed between rGFR and eGFR1, eGFR2, eGFR4, eGFR5 or eGFR6, and constant errors were observed between eGFR3 and rGFR, as revealed by the Passing & Bablok plot analysis. The Bland-Altman analysis illustrated that the 95% limits of agreement of all equations exceeded the previously accepted limits of <60 mL/min •1.73 m², except the equations of eGFR7 and eGFR8.

Conclusion

The newly developed formulas, eGFR7 and eGFR8, provide precise and accurate GFR estimation using serum CysC detection alone or in combination with serum Cr detection. Differences in detection methods should be carefully considered when choosing literature eGFR equations to avoid misdiagnosis and mistreatment.