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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE  
Year : 2020  |  Volume : 31  |  Issue : 6  |  Page : 1320-1330
Serum cystatin C unmasks renal dysfunction in cirrhosis and performs better in estimation of glomerular filtration rate


Department of Nephrology, Government Kilpauk Medical College, Chennai, Tamil Nadu, India

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Date of Web Publication29-Jan-2021
 

   Abstract 


In this study, we aimed to measure glomerular filtration rate (mGFR) using 99Tc DTPA in patients with Child-Pugh C cirrhosis and normal serum creatinine levels; and to compare the performance of creatinine and cystatin C-based equations [estimated GFRs (eGFRs)] to 99TcDTPA GFR in the same group. We selected a group of 65 consecutive patients with advanced liver cirrhosis and apparently normal renal function by serum creatinine alone. Patients with confounding and reversible factors were excluded. Demographic data, blood, urine, and imaging tests along with simultaneous measurement of serum creatinine and cystatin C were analyzed. The GFR was measured by 99Tc DTPAscintigraphy (mGFR) in 41 patients. We compared the performance of chronic kidney disease epidemiology collaboration (CKD-EPI-creatinine, CKD-EPI-cystatinC, CKD-EPI-creatinine-cystatinC) and Modification of Diet in Renal Disease equation equations for bias (mean difference), precision (root mean square error), and accuracy (P10 and P30). Bland–Altman plots were used to show the agreement of eGFR and mGFR. Twenty-five out of 41 patients (61%) had significant renal dysfunction (GFR ≤60 mL/min/ 1.73m2) by 99TcDTPA in our study and three patients were already in Stage 4 CKD. Unlike serum creatinine, serum cystatin C values were deranged in these patients. Among all GFR estimating formulae, CKD-EPI-creatinine-cystatinC combined equation had the least bias (-2.3), superior precision (7.1), highest P30 accuracy (78%), good sensitivity (87.5%), and best specificity (96%) in our study. Two-thirds of patients with cirrhosis had significant renal impairment despite having normal serum creatinine. Isolated serum creatinine values are misleading in cirrhosis. Cystatin C unmasks renal dysfunction in these patients. CKD-EPI-creatinine-cystatinC equation showed the best correlation and accuracy with 99TcDTPA GFR in our study. Creatinine based GFR estimation is fallacious in cirrhosis. Cystatin C and equations based on it may be worthwhile in liver disease.

How to cite this article:
Velayudham B, Thomas RG, Vasudevan C, Senthilkumar R P, Thirumalvalavan, Murugesan. Serum cystatin C unmasks renal dysfunction in cirrhosis and performs better in estimation of glomerular filtration rate. Saudi J Kidney Dis Transpl 2020;31:1320-30

How to cite this URL:
Velayudham B, Thomas RG, Vasudevan C, Senthilkumar R P, Thirumalvalavan, Murugesan. Serum cystatin C unmasks renal dysfunction in cirrhosis and performs better in estimation of glomerular filtration rate. Saudi J Kidney Dis Transpl [serial online] 2020 [cited 2021 May 12];31:1320-30. Available from: https://www.sjkdt.org/text.asp?2020/31/6/1320/308341



   Introduction Top


Renal function is an important predictor of outcome in advanced stages of liver cirrhosis.[1] Cirrhotic patients are susceptible to reversible as well as chronic kidney dysfunction because of altered hemodynamics, volume shifts, and comorbidities. Sustained intrarenal vasoconstriction secondary to circulatory dysfunction results in the progressive decline of glomerular filtration rate (GFR) and chronic kidney disease.[2]

Serum creatinine measurement and thereby GFR estimation is faulty[3] in cirrhosis due to: (1) defective synthesis of creatine, the precursor of creatinine in the liver,[4] (2) poor muscle mass and malnutrition,[5] (3) higher volume of distribution and (4) assay interference due to Jaffe positive compounds like bilirubin. Deceptively low creatinine values (<1 mg/dL) may mask significant decline in GFR. Accurate GFR estimation is necessary to avoid over-dosage of drugs and to plan early renal replacement therapy in the event of complications. There is a need to accurately diagnose and manage renal impairment co-existent with cirrhosis to improve outcomes. Kidney Disease: Improving Global Outcomes (KDIGO) 2012 Clinical Practice Guideline[6] suggests using additional tests in specific circumstances when eGFR based on serum creatinine is unreliable. The gold standard method for GFR measurement is urinary clearance of inulin during a continuous intravenous infusion. 99Tc DTPA scintigraphy is a less cumbersome, noninvasive, and easily available alternative method to inulin clearance that provides a close approximate for measured GFR (mGFR) in clinical studies.[6] Studies have reported that cystatin C-based GFR estimation is more accurate in cirrhosis than methods based solely on serum creatinine. Serum cystatin C is less influenced by most of the above limitations of creatinine[7] in liver disease [Figure 1]. Cystatin C is independent of muscle massage and sex so that the same reference interval applies to the whole population.[8] Drawbacks of cystatin-C are that it can be influenced by inflammation, infection and volume of distribution changes which are prevalent in the setting of cirrhosis. Whether cystatin C-based equations are reliable and can obviate the need for isotopic GFR measurements is still a matter of debate.
Figure 1: (a and b) Factors influencing creatinine and cystatin C levels in cirrhosis (factors that are most significant are highlighted in red).

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The purpose of this study was to evaluate the diagnostic superiority of cystatin C-based eGFRs in patients with Child-Pugh C[9],[10] stage liver cirrhosis using mGFR by 99Tc DTPA.


   Aim Top


In patients with advanced cirrhosis and apparently normal renal function, our aim was:

  1. To measure GFR by 99Tc DTPA scintigraphy (mGFR)
  2. To compare the performance of creatinine based [modification of diet in renal disease equation (MDRD) and CKD-EPI creatinine], Cystatin C based (CKD-EPI Cystatin C), and combined (CKD-EPI creatinine-cystatin C) equations with mGFR.



   Materials and Methods Top


Study population

This cross-sectional study was performed at a tertiary care center in South India between March and September 2018.We included 65 patients with Child-Pugh C cirrhosis between 18 and 55 years of age with serum creatinine<1 mg/dL.

The following patients were excluded from the study group:

  1. Patients with diabetes, hypertension, family history of chronic kidney disease, and those with acute kidney injury or hepatorenal syndrome
  2. Patients with dehydration, upper gastrointestinal bleed, sepsis, spontaneous bacterial peritonitis, tense ascites, aggressive paracentesis, acute liver decompensation in the previous month, or suspicion of hepatocellular carcinoma
  3. Patients with recent decline in urine output, proteinuria, active urinary sediments, or imaging abnormalities of the kidneys
  4. Patients with thyroid disease and usage of nonsteroidal anti-inflammatory drugs (NSAID), aminoglycosides, trimethoprim, or indigenous medicines.


Data regarding baseline demographic characteristics were collected. Model for End-Stage Liver Disease (MELD) scores [Table 1] were calculated for all patients. Simultaneous plasma samples for creatinine and cystatin C were collected and 99Tc DTPA renal dynamic scintigraphy was done in 41 patients with informed consent. The study was approved by the Institutional Ethics Committee.
Table 1: Equations used in the study.

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Patient selection [Figure 2]
Figure 2: Patient selection.

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Measurement of plasma creatinine (Pcr) and plasma cystatin C (PcysC)

Serum creatinine was measured by kinetic Jaffe’s method, using an automated biochemical analyzer (Roche Cobas c311) and commercially available assay kits by the same manufacturer. This assay uses “rate-blanking” to minimize interference by bilirubin. A correction factor is built-in for non-specific reactions due to pseudo-creatinine chromogens like proteins and ketones. The assay was standardized against IDMS. The detection limit was 0.17 mg/dL.

The normal reference interval of creatinine was as follows:

Adult males: 62–106 μmol/L (0.7–1.2 mg/dL) Females: 44–80 μmol/L (0.5–0.9 mg/dL)

Serum cystatin C was measured by a particle-enhanced turbidimetric immunoassay (PETIA) with a commercially available reagent set (Proton Biologicals, India) and read using semi-autoanalyser (Biosystem BTS-350). The detection limit was 0.1 mg/L. The intra- and inter-assay coefficient of variation (CV’s; n = 20) determined at 1.71 mg/L were <1.12% and <2.01% at 3.54 mg/L. Cystatin C measuring range was 0.2–8.0mg/L.

Normal reference interval of cystatin C was 0.56–1.25 mg/L (as per package insert).

mGFR measurement

mGFR was measured by 99Tc DTPA renal scintigraphy using the revised Gates equation as below.



Estimated glomerular filtration rate estimation

All eGFRs were calculated using the standardized formula given in [Table 1].


   Statistical Analysis Top


The parameters for assessment of eGFR equations in comparison to mGFR were based on KDIGO and National Kidney Foundation Kidney Disease Outcome Quality Initiative practice guidelines.[11]

  1. Bivariate correlation between eGFR and mGFR was tested by Pearson’s correlation method based on the normal distribution of the data (r). Lin’s concordance correlation coefficient (CCC) was also calculated
  2. Bias, precision, and accuracy of each eGFR equation were calculated. Bias (mean mGFR-eGFR) and precision were calculated by the root mean square error between eGFR and mGFR values. Accuracy was measured as the percentage of eGFRs varying by <10% (P10) and <30% (P30) from the corresponding mGFR value
  3. Receiver operating characteristic (ROC) plots were constructed and sensitivity and specificity at the cut-off value 60 mL/min/ 1.73 m2 were calculated based on area under the curve (AUC)
  4. Bland-Altman plot was used to analyze agreement between eGFR and mGFR.


Statistical software used were IBM SPSS Statistics for Windows version 23.0 (IBM Corp., Armonk, NY, USA) and R Studio. P <0.05 was taken as significant.


   Results Top


Patients

99Tc DTPA values of all patients according to GFR category are shown in [Table 2]. Sixty-one percent of patients had GFR ≤60 mL/min/1.73 m2 signifying moderate to severe renal dysfunction. Three patients had GFR<30 mL/min/ 1.73 m2. The baseline characteristics of 41 patients are shown in [Table 3]. The mean MELD score was 20.8 signifying advanced cirrhosis and 59% of patients had MELD score >20. Mean measured GFR of 41 patients was 55.2 ± 16.4 mL/min/1.73 m2 (mean ± standard deviation). The mean mGFR values were lower among those with MELD score ≥20 (51.3 ± 16.5 mL/min/1.73 m2) versus MELD <20 (60.7 ± 15 mL/min/1.73 m2), though it was not statistically significant. The median cystatin C values also differed between both MELD groups and this was statistically significant (P <0.05).
Table 2: Glomerular filtration rate categories of all 41 patients as per 99TcDTPA measured glomerular filtration rate.

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Table 3: Baseline demographics of 41 patients analyzed according to model for end stage liver disease severity of liver disease.

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Correlation, sensitivity, and specificity

Pearson’s correlation coefficient showed strong positive correlation between CKD-EPI-Creatinine-CysC (r = 0.9), CKD-EPI-CysC (r = 0.87) equations and measured GFR (P <0.001). Lin’s CCC confirmed these results [Table 4]. The positive correlation between these variables was consistent independent of MELD scores. ROC curves of eGFRs were constructed [Figure 3]. CKD-EPI-Creatinine-CysC and CKD-EPI-CysC had the best performance with AUC. Among the two equations, CKD-EPI-Creatinine-CysC had superior sensitivity (87.5%) and specificity (96%), whereas CKD-EPI-Cystatin C had poor sensitivity (31.3%) inspite of 100% specificity [Table 5]. eGFRs based solely on creatinine, MDRD and CKD-EPI-Cr had the least AUC (0.546 and 0.559, respectively).
Figure 3: Receiver operating characteristics plot of all estimated glomerular filtration rate equations.

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Table 4: Performance parameters of glomerular filtration rate predicting equations in the whole population and according to model for end-stage liver disease scores.

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Table 5: Performance of formulas at glomerular filtration rate 60mL/min/1.73m2, sensitivity and specificity based onreceiver operating characteristics.

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Bias, precision, accuracy and Bland Altman agreement

Mean bias was least (–2.3) and precision calculated as the root mean square of error was also lowest (7.1) for CKD-EPI-Creatinine-CysC equation [Table 6]. P30 accuracy of CKD-EPI-Creatinine-CysCeGFR was 78% in the entire population and improved to 83.3% in the group with a higher MELD score. The same equation showed the best agreement with mGFR on the Bland-Altman plot [Figure 4].
Figure 4: Bland-Altman plots showing, for each formula, the estimated GFR minus the measured GFR, bias (in mL/min/1.73 m2) in function of the measured GFR (TcDTPA in mL/min/1.73 m2) as reference standard in the whole population. The solid line represents the mean ratio. The broken lines represent the 95% limits of agreement (± 1.96 × standard deviation).
MDRD: Modification of Diet in Renal Disease equation, CKD-EPI-Cr: Chronic kidney disease epidemiology creatinine, CKD-EPI-Cr-CysC: CKD-EPI creatinine cystatin C, CKD-EPI-CysC: CKD-EPI cystatin C, GFR: Glomerular filtration rate.


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Table 6: Precision and bias of all equations in the population.

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   Discussion Top


Renal failure worsens the prognosis of patients with liver cirrhosis and contributes to a 7-fold rise in mortality.[12] Serum creatinine is included in MELD scoring system to prioritize patients for liver transplant worldwide.[13] In a study of 70 cirrhosis patients, Omar et al[14] demonstrated that creatinine based eGFRs overestimate renal function and have poor sensitivity and specificity (MDRD; 72.7%, 54.2% and CKD-EPI-Cr; 77.3%, 55.2%, respectively). GFR measurements by Haddadin have shown superior diagnostic accuracy of Cystatin C-based equations over others comparing with 99Tc DTPAGFR in cirrhosis. Although inulin is the gold standard for GFR measurement, 99Tc DTPAscintigraphy is a reasonably accurate, easily available and practical alternative to measure GFR.99TcDTPA has been employed as reference GFR by Omar et al[14] (70 patients) and Kim et al[15] (89 patients) in patients with cirrhosis. The findings of these studies are in line with Western reports using inulin,[16] iohexol[17] and 51Cr EDTA[18] and justifies the usage of 99TcDTPA as a close approximate of mGFR in resource-limited settings.

The present study was a single center experience at a tertiary care center catering to predominantly South Indian population. All patients had serum creatinine values <1 mg/dL. Unlike similar studies[14],[19] performed in Western countries, alcohol was the most common etiology for liver cirrhosis and viral hepatitis contributed only 12% to the total. The mean measured GFR (55.22 mL/min/1.73 m2) was lower than that reported in similar papers. Sixty-one percent of patients were categorized to moderate and severe renal dysfunction (GFR<60 mL/min/1.73 m2). The GFR ranged between 28 and 55 mL/min/1.73 m2 in this low GFR group. Nearly 7% of patients had stage 4 CKD. This finding highlights that significant renal failure is not uncommon in advanced cirrhosis even with normal creatinine. The magnitude of under-recognized renal dysfunction in this population is alarming and has therapeutic implications for the treating physician. Mean mGFR was lower (51.3 ± 16.5 mL/min/1.73 m2) in the sub-group with higher MELD scores. Similar findings were reported by De Souza et al[16] who classified patients by the degree of ascites. Those cirrhotics with refractory ascites had statistically significant lower mGFR values in this population (59 mL/min/1.73m2 vs. 83 mL/min/ 1.73 m2). In our study, while serum creatinine was <1 mg/dL in both MELD groups, median serum cystatin C values were significantly higher in the group with higher MELD scores (2.3 vs. 1.9 mg/L; P <0.05). Lower mGFR and higher cystatin C in this sub-group, confirm the results of Ustundang et al[20] that cystatin C levels correlate with GFR in each stage of liver failure and have diagnostic advantage in cirrhosis.

Creatinine-based equations, MDRD and CKD-EPI-Cr consistently overestimated renal function. These equations had poor P10 and P30 accuracy and large bias. Discriminative ability at 60 mL/min GFR for MDRD and CKD-EPI-Cr were abysmal (37.8% and 39%, respectively). These results match the conclusions of previous studies that creatinine-based eGFRs are misleading and underestimate renal dysfunction in cirrhosis. In comparison, both KDIGO 2012 CystatinC-based equations performed better across all stages of liver disease in our study. Among them, the CKD-EPI-Cr-CysC equation had the best precision and highest P10 and P30 accuracy when compared with the CKD-EPI-CyC formula [Table 6]. Bland-Altman graphs also showed the least mean bias and best agreement with the measured GFR favoring the CKD-EPI-Cr-CysC equation [Figure 4]. The diagnostic ability to detect CKD as a GFR below 60 mL/min/1.73 m2 was highest with the CKD-EPI-Cr-CysC equation (93.3%) compared to other test formulas (Table 6) as demonstrated by best ROC plots (AUC-0.985; sensitivity-87.5%; specificity – 96%). The study from Omar et al with similar methodology, has also reported superiority of CKD-EPI-Cr-CysC with sensitivity 77.3% and specificity 61.4%.{Table 6}

Our study has several strengths. Carefully structured inclusion and exclusion criteria enabled us to enroll in a homogeneous population with advanced cirrhosis. Those with exposures that could cause acute changes in renal function (recent use of aminoglycosides and NSAIDs) or influence cystatin C values (thyroid disease, diabetes, and steroid use) were excluded. Cystatin C estimation was done by PETIA which has shown good agreement with chromium-51 labeled ethylene-diaminetetraacetic acid (51Cr EDTA) GFR in published reports.[21]The results of our study are robust even though the sample size was relatively small because we have used the isotopic GFR as reference. 99Tc-DTPA is relatively inexpensive, has low radiation dose and its clearance correlates well[22] with 51Cr-EDTA, the radionuclide of choice for GFR measurement. Recent reports in 2015 from Kim et al[23] in a post-nephrectomy population have shown that 99Tc-DTPA scintigraphy by revised Gates equation correlated well with 51Cr-EDTA GFR’s and was not inferior to iothalamate or iohexol measurements especially in patients with low GFR values.

The study has certain limitations. All participants were from a single centre of uniform ethnicity and predominantly males with alcoholic cirrhosis. The sample size, though statistically adequate, was smaller than some other validation studies of estimating equations. The volume of distribution and kinetics of 99Tc-DTPA into the third space in cirrhosis have not been studied adequately. Actually, such a flaw should result in systematic over-estimation of GFR rather than its underestimation. Furthermore, the influence of smoking on cystatin C measurements has not been analyzed.

Based on our study, in patients with advanced cirrhosis, we suggest physicians to consider combined creatinine and cystatin C-based equation when a true estimate of GFR is required.


   Conclusions Top


  1. Sixty-one percent of patients with advanced cirrhosis had significant renal dysfunction (GFR ≤60 mL/min/1.73 m2) by 99Tc-DTPA despite normal serum creatinine. Serum creatinine and creatinine-based eGFR is fallacious and misleading in cirrhosis
  2. Cystatin C can unmask renal failure in these patients. CKD-EPI-Creatinine-CystC equation showed the best correlation and accuracy with DTPAGFR in our study.


Conflict of interest: None declared.



 
   References Top

1.
Nair S, Verma S, Thuluvath PJ. Pretransplant renal function predicts survival in patients undergoing orthotopic liver transplanatation. Hepatology 2002;35:1179-85.  Back to cited text no. 1
    
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GinèsP, SchrierRW. Renal failure in cirrhosis. N Engl J Med2009;361:1279-90.  Back to cited text no. 2
    
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Sherman DS, Fish DN, Teitelbaum I. Assessing renal functions in cirrhotic patients: problems and pitfalls. Am J Kidney Dis 2003; 41:269-78.  Back to cited text no. 4
    
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Mindikoglu AL, Regev A, Seliger SL, Magder LS. Gender disparity in liver transplant waiting-list mortality: the importance of kidney function. Liver Transpl 2010;16:1147-57.  Back to cited text no. 5
    
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KDIGO 2012 Clinical practice guideline for the evaluation and management of chronic kidney disease-Guideline-1.4.3.2. Kidney International Supplements 2013;3:5-14.  Back to cited text no. 6
    
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Parikh CR, Belcher JM. Reconsidering a “chopped liver”: the need for improving glomular filtration rate estimation for hepatic transplantation.Hepatology2014;59:1242-5.  Back to cited text no. 7
    
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Haddadin Z, Lee V, Conlin C, et al. Comparison of performance of improved serum estimators of glomerular filtration rate (GFR) to 99Tc DTPAGFR methods in patients with hepatic cirrhosis. J Nucl Med Technol 2017:45;42-9.  Back to cited text no. 8
    
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Pugh RN, Murray-Lyon IM, Dawson JL, Pietroni MC, Williams R. Transection of the oesophagus for bleeding oesophagealvarices. Br J Surg 1973;60:646-9.  Back to cited text no. 9
    
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National Kidney Foundation. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis 2002;39:S1-266.  Back to cited text no. 11
    
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Fede G, D’Amico G, Arvaniti V, et al. Renal failure and cirrhosis: a systematic review of mortality and prognosis. J Hepatol 2012;56: 810-8.  Back to cited text no. 12
    
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Brown RS Jr, Lake JR. The survival impact of liver transplantation in the MELD era, and the future for organ allocation and distribution. Am J Transplant 2005;5:203-4.  Back to cited text no. 13
    
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Omar M, Abdel-Razek W, Abo-Raia G, Assem M, El-Azab G. Evaluation of Serum Cystatin C as a Marker of Early Renal Impairment in Patients with Liver Cirrhosis. Int J Hepatol 2015;2015:309042.  Back to cited text no. 14
    
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Kim JD, Kang HS, Cho HS, et al. Serum cystatin C level is a useful marker for the evaluation of renal function in patients with cirrhotic ascites and normal serum creatinine levels Korean J Hepatol 2011;17:130-8.  Back to cited text no. 15
    
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DeSouza V, Hadj-Aissa A, Dolomanova O, et al. Creatinine-versus cystatine C-based equations in assessing the renal function of candidates for liver transplantation with cirrhosis. Hepatology 2014;59:1522-31.  Back to cited text no. 16
    
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Mindikoglu AL, Dowling TC, Weir MR, Seliger SL, Christenson RH, Magder LS. Performance of chronic kidney disease epidemiology collaboration creatinine-cystatin C equation for estimating kidney function in cirrhosis. Hepatology 2014;59:1532-42.  Back to cited text no. 17
    
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Xirouchakis E, Marelli L, Cholongitas E, et al. Comparison of cystatin C and creatinine-based glomerular filtration rate formulas with 51Cr-EDTA clearance in patients with cirrhosis. Clin J Am Soc Nephrol 2011;6:84-92.  Back to cited text no. 18
    
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Orlando R, Mussap M, Plebani M, et al. Diagnostic value of plasma cystatin C as a glomerular filtration marker in decompensated liver cirrhosis.Clin Chem 2002;48:850-8.  Back to cited text no. 19
    
20.
Ustundag Y, Samsar U, Acikgoz S, et al. Analysis of glomerular filtration rate, serum cystatin C levels, and renal resistive index values in cirrhosis patients. Clin Chem Lab Med 2007;45:890-4.  Back to cited text no. 20
    
21.
Simonsen O, Grubb A, Thysell H. The blood serum concentration of cystatin C (y-trace) as a measure of the glomerular filtration rate. Scand J Clin Lab Invest 1985;45:97-101.  Back to cited text no. 21
    
22.
Hilson AJ, Mistry RD, Maisey MN. 99Tcm-DTPA for the measurement of glomerular filtration rate.Br J Radiol 1976;49:794-6.  Back to cited text no. 22
    
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Kim Y, So Y, Ha S, et al. Improved measurement of the glomerular filtration rate from Tc99m DTPAscintigraphy in patients following nephrectomy. EurRadiol 2014:24:413-22.  Back to cited text no. 23
    

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Correspondence Address:
Remi George Thomas
Department of Nephrology, Government Kilpauk Medical College, Chennai, Tamil Nadu
India
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DOI: 10.4103/1319-2442.308341

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
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