Pediatr Nephrol (2013) 28:647–653 DOI 10.1007/s00467-012-2366-7
ORIGINAL ARTICLE
Cystatin C in children on chronic hemodialysis Olivera Marsenic & Andrea Wierenga & Donna R. Wilson & Michael Anderson & Tripti Shrivastava & Garfield A. Simon & Anne M. Beck & Tiffany J. Swanson & Kathleen Studnicka & Dorit Elberg & Kevin Couloures & Martin A. Turman
Received: 17 August 2012 / Revised: 28 September 2012 / Accepted: 16 October 2012 / Published online: 21 November 2012 # IPNA 2012
Abstract Background Cystatin C (CyC) concentration has been suggested as a marker of middle-molecule accumulation, hemodialysis (HD) adequacy and for estimating residual renal function (RRF), but it has not been studied in pediatric HD. High CyC is associated with increased cardiovascular disease (CVD). We investigated CyC kinetics and the effect of RRF on CyC in a pediatric HD population. Methods A total of 21 HD sessions and 20 interdialytic periods were analyzed in seven patients, age 5–19 years, of whom four were anuric (A) and three were non-anuric (NA). CyC was measured before (preHD) and after (postHD) three standard HD sessions in 1 week and prior to the first session of the following week. Results We found no difference (p00.67) in CyC concentration between preHD CyC (9.85±2.15 mg/l; A vs. NA, p0 0.37) and postHD CyC (10.04±2.83 mg/l; A vs NA, p0 0.28). The weekly average preHD CyC median concentration was 10.14 mg/l (A vs. NA, p00.87) and correlated with age (r00.808, p00.03) and height measurement (r00.799,
O. Marsenic (*) : D. R. Wilson : A. M. Beck : T. J. Swanson : K. Studnicka : M. A. Turman Pediatric Nephrology, Oklahoma University Health Sciences Center, 1200 N. Phillips Ave., Suite 14200, Oklahoma City, OK 73104, USA e-mail:
[email protected] A. Wierenga : T. Shrivastava : G. A. Simon : D. Elberg Biochemical Genetic Laboratory, Oklahoma University Health Sciences Center, Oklahoma City, OK, USA M. Anderson Department of Biostatistics and Epidemiology, Oklahoma University Health Sciences Center, Oklahoma City, OK, USA K. Couloures Pediatric Critical Care, Oklahoma University Health Sciences Center, Oklahoma City, OK, USA
p00.03), but not with RRF, single-pool Kt/V, ultrafiltration, HD duration or blood liters processed. Conclusions Cystatin C is very elevated in children on HD. It does not rise between HD sessions, is not removed by standard HD and remains at steady state; therefore, elimination is extrarenal. Low RRF does not affect CyC elimination. CyC increases with age and height. If a high CyC concentration can be proven to have a causative role in the development of CVD, routine intensified HD regimens in children may be indicated for its removal. Keywords Pediatric hemodialysis . Glomerular filtration rate . Biomarkers . Hemodialysis adequacy . Residual renal function
Introduction Cystatin C (CyC), a 13-kDa protein produced by all nucleated cells, is an inhibitor of endogenous cystine proteases, with molecular characteristics that make it a suitable marker for assessing renal or dialysis clearance. It is believed that its plasma level is not influenced by age, sex, muscle mass and body mass index, it is distributed extracellularly, its production is constant, it is freely circulating, it is freely filtered across glomerular basement membrane and it is reabsorbed and metabolized in the proximal tubule [1–4]. Extrarenal clearance of CyC is not well described [5, 6] but has been demonstrated in rats [4] and humans [7, 8]. CyC has been shown to be superior to serum creatinine for the estimation of glomerular filtration rate (GFR) [5, 9, 10]. Elevated CyC levels have been associated with increased cardiovascular disease (CVD) risk, both with and without renal impairment [11–17], but the link between high CyC and the risk of CVD is still unclear. In the absence of renal impairment, elevated CyC was found to enhance the cardiovascular risk factor profile in obese children [12] and to correlate with
648
Pediatr Nephrol (2013) 28:647–653
atherosclerosis progression [16, 17]. If CyC is proven to have a causative role in the development of CVD, its removal may be beneficial as a means to improve cardiovascular outcomes. Data on CyC in dialysis patients are scarce. A few adult studies investigated CyC as marker of middle molecule (MM) clearance in hemodialysis (HD) and showed its clearance to be influenced by dialysis intensity, larger membrane pore size and blood liters processed [2, 18–21]. CyC has been suggested as a marker for estimating residual renal function (RRF) in adults on HD and peritoneal dialysis (PD), and in children on PD [22–24], but it has not been studied in the pediatric HD population [24]. The aims of our study were to: (1) describe CyC kinetics during and between HD sessions to assess its rate of interdialytic production, possible extrarenal elimination and clearance by HD and (2) examine the effect of RRF on CyC.
Methods Patients and HD characteristics This pilot study was performed in children with end-stage renal disease (ESRD) receiving chronic HD at the pediatric HD unit of Oklahoma University Health Sciences Center (OUHSC) and was approved by the Institutional Review Board (IRB #15425). All patients and their parents/guardians provided informed consent and assent (age 12– 16 years). All subjects were stable on three-times-weekly HD. Intradialytic blood volume monitoring was used to monitor ultrafiltration and optimize volume status. None of the subjects had previously abnormal thyroid function tests or had an acute illness or received steroids prior or during the study. C-reactive protein was not measured since it is commonly elevated in children on HD [25] and has been reported not to influence CyC levels [2, 8, 18, 26]. Thyroid function tests were not done during the study as all subjects were previously euthyroid [27, 28], and earlier studies in HD patients showed no relationship between CyC and thyroid-stimulating hormone [2, 18]. All patients with residual urine output collected urine for 24 h for estimation of RRF. RRF was calculated as the mean of urea and creatinine clearance and normalized to 1.73 m2 surface area [29]. Functional anuria was defined as urine volume of 0.05 P>0.05
HD, Hemodialysis Data are presented as the means ± SD for normally distributed data or as the median with interquartile range (IQR; 25 %, 75 %) for data not normally distributed a
n027; average of 4 predialysis results for 6 subjects (inclusive of 3-day interdialytic weekend interval) and 3 predialysis results for 1 subject (received a kidney transplant prior to time of last predialysis sample)
b
P>0.05, postdialysis vs. predialysis (n021 HD sessions)
c
P>0.05, 60-min postdialysis vs. postdialysis after 1st HD (n07 HD sessions)
allows assessment of the MM burden and removal of MM with various dialysis intensities. MM are poorly removed with low-flux HD; in contrast, their removal with hemodiafiltration (HDF) has been shown to result in better outcomes in children
[33–35]. However, intensified HD regimens are not routinely utilized in children. Most children in the USA receive threetimes-weekly low-flux HD as 3 to 5-h sessions. Secondly, CyC as marker of GFR: the analysis of interdialytic changes in CyC allows assessment of its interdialytic accumulation and elimination, and an assessment of RRF. CyC is a preferred marker of GFR [5, 9, 10] and studying its handling in ESRD may bring new insights into its extrarenal elimination. Thirdly, CyC as risk factor for CVD: elevated CyC is associated with higher incidence of CVD [11–17]. Its monitoring and removal may be beneficial if it is found to have a direct role in the development of CVD. We have shown that CyC is very elevated in children on standard HD, with a weekly pre-HD median of 10.14 mg/l. The normal range in children and adults is 0.7–1.38 [36] and 0.57–1.12 mg/l, respectively [37]. The mean CyC concentration in anuric children on PD has been reported to be 9.4 mg/l [23]. Elevated CyC has been associated with a Table 3 Pearson correlation of mean weekly predialysis cystatin C with various variables
Fig. 1 a Mean cystatin C (CyC) before and after hemodialysis (HD) over a 1-week period. Dotted lines Lower and upper limit of normal, respectively, in children (0.7–1.38 mg/l) [36]. b Mean blood urine nitrogen (BUN) before and after HD over a 1-week period. Dotted lines Lower and upper limit of normal, respectively, in children (7– 20 mg/dl)
Variable
Correlation coefficient r
P
Age (years) Weight (kg) Height (cm) Body surface area (m2) RRF (ml/min/1.73 m2) Weekly total HD duration (min) Blood liters processed (l/kg) Weekly total spKt/V URR (%) UF (%)
0.808 0.471 0.799 0.583 0.064 0.250 0.129 0.011 0.064 0.083
0.03 0.28 0.03 0.17 0.89 0.59 0.78 0.98 0.89 0.86
RRF, Residual renal function; URR, urea reduction ratio; UF, ultrafiltration
Pediatr Nephrol (2013) 28:647–653
higher incidence of CVD [11–17]. Early markers of atherosclerosis are frequently present in children on maintenance dialysis, and cardiopulmonary/cardiac disease is the most common cause of death in this population [38, 39]. However, it is unknown if CyC has a direct role in the development of cardiovascular events. CyC is a cystine protease inhibitor that regulates lysosomal proteases such as cathepsins. The cathepsins play a role in extracellular matrix degradation and are involved in vascular remodeling with their elastolytic activity [17, 40]. The imbalance between proteases and inhibitors due to vascular micro-inflammation has been suggested to be an atherogenic mechanism [41], but it is unclear if systemically elevated CyC has an atherogenic effect. If CyC is proven to have a direct role in development of CVD, its removal may be important to improve outcomes in children on maintenance dialysis. Our analysis of intra-dialytic changes of CyC showed that CyC is not removed by standard HD, regardless of single-treatment spKt/V, total weekly spKt/V, HD duration, UF and blood liters processed. High single treatment spKt/V delivered in our study (mean 2.09) did not affect CyC concentration, showing that increasing the dialysis dose in low-flux HD does not improve CyC removal. Studies in adults on low-flux HD showed that CyC is not removed [21] or that its removal is minimal and variable with a CyC RR of 11.5±16.2 % [19]. This is improved with high-flux HD achieving a CyC RR of 42.4±6.3 % [19] and 26.1± 11.8 % [2]. HDF results in the best CyC reduction of 72 %, and the post-HDF CyC level closest to normal at 1.78 mg/ l (1.27–2.29) [21]. These results suggest that more frequent or longer low-flux HD will not reduce CyC and other MM and that treatments utilizing membranes with larger pore size and larger convective transport are needed for their removal. HD modalities that increase MM removal result in better outcomes in children [33–35], but these are not routinely utilized. We found that CyC does not reequilibrate 1 h after HD, which is in agreement with adult studies in HD, hemofiltration or HDF [21]. Consequently, its immediate post-HD concentration can be used for assessment of its clearance. In the analysis of interdialytic periods, including the 3day interval between a Friday and Monday HD session, we found there was no interdialytic rise of CyC, with CyC remaining at steady state. Most studies of CyC and HD have investigated CyC changes for a single HD session [18, 19, 21]. One adult study analyzed CyC over a 1-week period in patients on high-flux HD [2] and found a reduction of 26.1 ± 11.8 % during HD and no differences between pre-HD values. Since there was no CyC removal during HD in our study, we assume that any CyC that is generated is continuously eliminated extrarenally. We found that low RRF had no effect on CyC concentration, with no difference in CyC between anuric and non-anuric children. CyC is thought be
651
eliminated by the kidney and, therefore, the best marker of GFR [1, 5, 9, 10]. CyC has also been suggested as a marker for the estimation of RRF in adults on HD and PD [22], and in children on PD [23], based on serum CyC measurements at a single HD session or a single PD visit. The interval serum CyC changes were not analyzed in these studies, and the assumption was made that lower CyC is the result of RRF alone. The study by Kim at al. (performed using a single serum CyC measurement in 20 children on PD on the morning post overnight PD) showed a lower CyC in the non-anuric group [23], although the RRF in that group was higher than that in our study cohort (4–9.3 vs. 1.54–1.75 ml/ min/1.73 m2, respectively), suggesting that higher RRF may contribute to CyC elimination. Extrarenal elimination of CyC has been recognized [5, 6]. Sjöström et al. studied the CyC production rate and non-renal elimination in patients with various GFR and on dialysis and reported CyC production rate of 0.124 ± 0.023 mg/min/1.73 m2 and a nonrenal clearance of 22.3 ml/min/1.73 m2 [7]. In their subsequent work in adults on HD with and without RRF, these authors concluded that CyC cannot be used for calculating low GFR [8]. Our results are consistent with these findings and suggest that in ESRD patients, extrarenal elimination is likely to be significant, providing steady state of CyC. We found that low GFR does not affect CyC. We found a significant correlation between the predialysis CyC concentration and patient age and height. The largest discrepancy was noted in the youngest anuric patient, age 5 years, whose predialysis CyC was lower (range 5.85– 6.14 mg/l). This difference could not be attributed to any other feature of this patient. Although CyC level is thought to be independent of age, height, weight and body mass [1, 3, 5], including body cell mass in the calculation has been found to improve the accuracy of GFR estimation from CyC [9]. Our results indicate that in ESRD patients, where CyC is not removed by HD or low RRF, serum CyC levels reflect the total CyC retained. Since CyC is thought to have extracellular distribution [2, 18], its level will be affected by the amount of extracellular fluid (ECF), which in turn is dependent on patient size and body composition [24]. This should be kept in mind when interpreting serum CyC levels in children with ESRD, either on PD or HD, as lower serum CyC may represent the effect of the patient’s lower ECF volume and body composition rather than a higher RRF. Our pilot study included 21 HD sessions, 20 interdialytic periods and seven subjects with a limited range of RRF. Although our findings are not generalizable, they raise important concerns regarding HD adequacy, extrarenal elimination of CyC and cardiovascular risk in children on chronic HD that need to be addressed in a larger group of children on HD. This is the first study of CyC in the pediatric HD population and the only study that has investigated pediatric CyC
652
handling and kinetics over a 1-week period. We reached important novel conclusions. CyC (and likely other MM) is not removed by standard HD and is very elevated. If high CyC is proven to have a causative role in the development of CVD, routine intensified HD regimens that utilize membranes with a larger pore size and larger convective transport may be indicated for its removal. If CyC is found to be decreased in children receiving these HD treatments, then CyC could be used as a marker for MM for monitoring the adequacy of intensified HD. CyC does not rise between HD sessions, is not removed by standard HD or low RRF and remains at steady state. Therefore, the elimination of CyC is likely to be extrarenal. CyC in ESRD patients increases with age and size in the absence of its removal by HD or RRF. This may be related to CyC distribution in the ECF, which is dependent on patient size and body composition. Our findings require confirmation on a larger number of children of various ages, with both anuria and a wider range of RRF. If confirmed, this knowledge may significantly influence the current view of CyC as a GFR marker as well as current practice of HD in children. Acknowledgments We thank Dr Terrence Stull, Chairman, Department of Pediatrics, OUHSC, for his support.
References 1. Sharma AP, Kathiravelu A, Nadarajah R, Yasin A, Filler G (2009) Body mass does not have a clinically relevant effect on cystatin C eGFR in children. Nephrol Dial Transplant 24:470–474 2. Huang SH, Filler G, Yasin A, Lindsay RM (2011) Cystatin C reduction ratio depends on normalized blood liters processed and fluid removal during hemodialysis. Clin J Am Soc Nephrol 6:319– 325 3. Zaffanello M, Franchini M, Fanos V (2007) Is serum Cystatin-C a suitable marker of renal function in children? Ann Clin Lab Sci 37:233–240 4. Tenstad O, Roald AB, Grubb A, Aukland K (1996) Renal handling of radiolabelled human cystatin C in the rat. Scand J Clin Lab Invest 56:409–414 5. Bacchetta J, Cochat P, Rognant N, Ranchin B, Hadj-Aissa A, Dubourg L (2011) Which creatinine and cystatin C equations can be reliably used in children? Clin J Am Soc Nephrol 6:552–560 6. Inker LA, Schmid CH, Tighiouart H, Eckfeldt JH, Feldman HI, Greene T, Kusek JW, Manzi J, Van Lente F, Zhang YL, Coresh J, Levey AS, Investigators CKD-EPI (2012) Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med 367:20–29 7. Sjöström P, Tidman M, Jones I (2005) Determination of the production rate and non-renal clearance of cystatin C and estimation of the glomerular filtration rate from the serum concentration of cystatin C in humans. Scand J Clin Lab Invest 65:111–124 8. Sjöström PA, Jones IL, Tidman MA (2009) Cystatin C as a filtration marker: haemodialysis patients expose its strengths and limitations. Scand J Clin Lab Invest 69:65–72 9. Andersen TB, Jødal L, Boegsted M, Erlandsen EJ, Morsing A, Frøkiær J, Brøchner-Mortensen J (2011) GFR prediction from
Pediatr Nephrol (2013) 28:647–653 Cystatin C and Creatinine in children: effect of including body cell mass. Am J Kidney Dis 59:50–57 10. Sharma AP, Yasin A, Garg AX, Filler G (2011) Diagnostic accuracy of Cystatin C–based eGFR equations at different GFR levels in children. Clin J Am Soc Nephrol 6:1599–1608 11. Patel PC, Ayers CR, Murphy SA, Peshock R, Khera A, de Lemos JA, Balko JA, Gupta S, Mammen PP, Drazner MH, Markham DW (2009) Association of cystatin C with left ventricular structure and function: the Dallas Heart Study. Circ Heart Fail 2:98–104 12. Codoñer-Franch P, Ballester-Asensio E, Martínez-Pons L, Vallecillo-Hernández J, Navarro-Ruíz A, Valle-Pérez R (2011) Cystatin C, cardiometabolic risk, and body composition in severely obese children. Pediatr Nephrol 26:301–307 13. Ix JH, Shlipak MG, Chertow GM, Whooley MA (2007) Association of cystatin C with mortality, cardiovascular events, and incident heart failure among persons with coronary heart disease: data from the Heart and Soul Study. Circulation 115:173–179 14. Menon V, Shlipak MG, Wang X, Coresh J, Greene T, Stevens L, Kusek JW, Beck GJ, Collins AJ, Levey AS, Sarnak MJ (2007) Cystatin C as a risk factor for outcomes in chronic kidney disease. Ann Intern Med 147:19–27 15. Shin MJ, Song SH, Kwak IS, Lee SB, Lee DW, Seong EY, Kim IY, Rhee H, Lee N (2012) Serum cystatin C as a predictor for cardiovascular events in end-stage renal disease patients at the initiation of dialysis. Clin Exp Nephrol 16:456–463 16. Imai A, Komatsu S, Ohara T, Kamata T, Yoshida J, Miyaji K, Shimizu Y, Takewa M, Hirayama A, Deshpande GA, Takahashi O, Kodama K (2011) Serum cystatin C is associated with early stage coronary atherosclerotic plaque morphology on multidetector computed tomography. Atherosclerosis 218:350–355 17. Taglieri N, Koenig W, Kaski JC (2009) Cystatin C and cardiovascular risk. Clin Chem 55:1932–1943 18. Al-Malki N, Heidenheim PA, Filler G, Yasin A, Lindsay RM (2009) Cystatin C levels in functionally anephric patients undergoing dialysis: the effect of different methods and intensities. Clin J Am Soc Nephrol 4:1606–1610 19. Park JS, Kim GH, Kang CM, Lee CH (2010) Application of Cystatin C reduction ratio to high-flux Hemodialysis as an alternative indicator of the clearance of middle molecules. Korean J Intern Med 25:77–81 20. Krieter DH, Hackl A, Rodriguez A, Chenine L, Moragues HL, Lemke HD, Wanner C, Canaud B (2010) Protein-bound uraemic toxin removal in haemodialysis and post-dilution haemodiafiltration. Nephrol Dial Transplant 25:212–218 21. Lindstrom V, Grubb A, Hegbrant MA, Christensson A (2008) Different elimination patterns of b-trace protein, b2-microglobulin and cystatin C in haemodialysis, haemodiafiltration and haemofiltration. Scand J Clin Lab Invest 68:685–691 22. Hoek FJ, Korevaar JC, Dekker FW, Boeschoten EW, Krediet RT (2007) Estimation of residual glomerular filtration rate in dialysis patients from the plasma cystatin C level. Nephrol Dial Transplant 22:1633–1638 23. Kim SJ, Sohn YB, Park SW, Jin DK, Paik KH (2011) Serum Cystatin C for estimation of residual renal function in children on peritoneal dialysis. Pediatr Nephrol 26:433–440 24. Filler G, Huang SS, Lindsay RM (2011) Residual renal function assessment with cystatin C. Pediatr Nephrol 26:333–335 25. Goldstein SL, Currier H, Watters L, Hempe JM, Sheth RD, Silverstein D (2003) Acute and chronic inflammation in pediatric patients receiving hemodialysis. J Pediatr 143:653–657 26. Grubb A, Björk J, Nyman U, Pollak J, Bengzon J, Ostner G, Lindström V (2011) Cystatin C, a marker for successful aging and glomerular filtration rate, is not influenced by inflammation. Scand J Clin Lab Invest 71:145–149
Pediatr Nephrol (2013) 28:647–653 27. Özden TA, Tekerek H, Bafl F, Darendeliler F (2010) Effect of hypo-and euthyroid status on serum cystatin C levels. J Clin Res Ped Endo 2:155–158 28. Manetti L, Pardini E, Genovesi M, Campomori A, Grasso L, Morselli LL, Lupi I, Pellegrini G, Bartalena L, Bogazzi F, Martino E (2005) Thyroid function differently affects serum cystatin C and creatinine concentrations. J Endocrinol Invest 28:346– 349 29. European best practice guidelines for haemodialysis (part 1) (2002) Measurement of residual renal function in HD. Nephrol Dial Transplant 17:11–15 30. Gehan E, George SL (1970) Estimation of human body surface area from height and weight. Cancer Chemother Rep 54:225–235 31. Daugirdas JT (1993) Second generation logarithmic estimates of single-pool variable volume Kt/V: an analysis of error. J Am Soc Nephrol 4:1205–1213 32. KDOQI Clinical practice guidelines for hemodialysis adequacy (2006) Guideline 3. Methods for postdialysis blood sampling. Am J Kidney Dis 48:S24–S27 33. Fischbach M, Fothergill H, Zaloszyc A, Menouer S, Terzic J (2011) Intensified daily dialysis: the best chronic dialysis option for children? Semin Dial 24:640–644
653 34. Fischbach M, Fothergill H, Zaloszyc A, Seuge L (2012) Hemodiafiltration: the addition of convective flow to hemodialysis. Pediatr Nephrol 27:351–356 35. Fischbach M, Hamel G, Koehl C, Geisert J (1989) Beta-2microglobulin in hemodiafiltered children: long-term efficiency follow-up. Nephron 53:110–114 36. Bökenkamp A, Domanetzki M, Zinck R, Schumann G, Brodehl J (1998) Reference values for cystatin C serum concentrations in children. Pediatr Nephrol 12:125–129 37. Köttgen A, Selvin E, Stevens LA, Levey AS, Van Lente F, Coresh J (2008) Serum cystatin C in the United States: the Third National Health and Nutrition Examination Survey (NHANES III). Am J Kidney Dis 51:385–394 38. Mitsnefes MM (2012) Cardiovascular disease in children with chronic kidney disease. J Am Soc Nephrol 23:578–585 39. North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) (2011) Dialysis patient characteristics. In: NAPRTCS (ed) Annual dialysis report. NAPRTCS, Boston, pp 1–18 40. Newman DJ (2002) Cystatin C. Ann Clin Biochem 39:89–104 41. Bökenkamp A, Herget-Rosenthal S, Bökenkamp R (2006) Cystatin C, kidney function and cardiovascular disease. Pediatr Nephrol 21:1223–1230
