Cystatin C A Clinician‘s Perspective

1. Cystatin C A Clinician‘s Perspective Cystatin C A Clinician‘s Perspective A. Bökenkamp, MD PhD Pediatric Nephrology, Vrije Universiteit Medical Center, Amsterdam (NL) A. Bökenkamp, MD PhD Pediatric Nephrology, Vrije Universiteit Medical Center, Amsterdam (NL)

2. „Cystatin C = potential renal function parameter“ Publications on Cystatin C since 1985 Development of automated test kits

3. Variability of 24-hour Creatinine-Clearance Coefficient of Variation (%) 10 consecutive measurements in 16 children (10m, 6f),mean age 12 years 70 60 50 40 30 20 10 0 S-Crea Schwartz cCrea Crea excretion Urine flow Bökenkamp et al, unpublished

4. Clinical Indications for the Assessment of Kidney Function GFR in "Steady State" Changes in GFR Kidney functionon dialysis Korrelation mit Inulin clearance Dialysis Kidney Transplantation ARF Reference range Correlation withgold-standard GFR

5. Serum Creatinine- Children - Creatinine [µmol/L] Age [years] Bökenkamp et al, Ped Nephrol 1998

6. Serum Cystatin C - Children - Cystatin C [mg/L] Reference range> 1st year of life 0.7 - 1.38 mg/L (PETIA) Age [years] Bökenkamp et al, Ped Nephrol 1998

7. Reference Values for Cystatin C - PETIA vs. PENIA - Children Range PETIA (DAKO) 0.70 - 1.38 mg/L[n = 187, Pediatr. Nephrol. 12 (1998): 125-9] PENIA (Behring) 0.51 - 0.95 mg/L[n = 96, Clin.Chem 45 (1999): 1856-8] Adults Range PETIA (DAKO) 0.70 - 1.21 mg/L [n = 121, Scand.J.Clin.Lab.Invest. 57 (1997): 463-70] PENIA (Behring) 0.50 - 0.98 mg/L [n = 139, Clin.Chem. 47 (2001): 2031-3]

8. Polymorphisms in the Cystatin C Promotor Serum Cys C (mg/l) • Combined presence of impairing polymorphisms -82 G/C, -78 T/G, -5 G/A, + 4 A/C, +148 G/A • N = 639 healthy men age 50 years • Frequency of haplotypes- wild-type 75%- mutant except pos. -5: 20%- mutant in all positions: 5% P < 0.01 Eriksson et al, Arterioscler Throm Vasc Biol 2004

9. Cystatin C in Spina bifida N = 27 children Abnormal GFR in 3/27 DTPA-clearance Cut-off 90 ml/min/1.73m2 Cystatin C (AUC 0.952 ± 0.051) Schwartz-GFR (AUC 0.764 ± 0.125) P < 0.05 Filler et al, J.Urol. 2003

10. 74.835 GFR estim. = —————— CysC 1/0.75 Formula calculated by regression analysis between serum Cysatin C and inulin clearance in 209 patients with different underlying renal disease. CyC based formula for GFR estimation Dade Behring, 2004

11. 146 125J-Iothalamate-clearances in 123 adults (median age 50 y) • Median GFR 81 ml/min/1.73m2 [12 - 157] • Linear regression: GFR ~ 80/CysC - 4.3 Performance of GFR-Prediction Formulae in Adults Cystatin C Cockcroft & Gault Mean diff. -2,4 [-26.1 to 21.3 ml/min/1.73m2] Mean diff. 15.9 [-14.4 to 46.1 ml/min/1.73m2] Hoek et al, NDT 2003

12. Performance of GFR-Prediction Formulae in Children Cystatin C Counahan-Schwartz logGFR ~ 1.962 + 1.123 * log (1/CysC) GFR ~ height * k / creatinine[k = 38, in pubertal boys k = 48] Filler et al, Pediatr.Nephrol. 2003

13. Imprecision of Different Formulae for the Prediction of GFR- MDRD-Study, n = 558 - Intraindividual variability of inulin clearance ~10% Levey et al, Ann. Intern. Med. 1999

14. Scatter between Surrogate GFR Markers and CIothalamate Perkins et al, JASN 2005

15. Prediction of GFR from Serum MarkersA Fata Morgana? • Wide confidence intervals for GFR-prediction formulae using different markers. • May in part reflect variability of the „Golden Standard“ itself. • In clinical practice, calculation of a surrogate GFR is still useful. • Cystatin C-derived formulae perform at least equally to creatinine-based formulae. • Cystatin C-based GFR-estimations are independent of anthropomorphometric data and can be done directly in the lab. • In situations with alterations in creatinine production, Cystatin C is mandatory

16. Clinical Indications for the Assessment of Kidney Function GFR in "Steady State" Changes in GFR Kidney functionon dialysis Korrelation mit Inulin clearance Dialysis Kidney Transplantation ARF Reference range Correlation withgold-standard GFR

17. Is Cystatin C Eliminated by Dialysis? • No significant elimination by conventional hemodialysis (Kabanda et al: Kidney Int. 46 (1994): 1689 - 96) • No significant elimination by peritoneal dialysis(Kabanda et al: Kidney Int. 48 (1995): 1946 - 52) Cystatin C ß2-Microglobuline Molecular weight 13.3 kDa 11.8 kDa Reference range 0.7 - 1.4 mg/l 0.4 - 2.3 mg/l Concentration pre-HD 7 - 11 mg/l 40 - 60 mg/l x 10 x 30 - 100

18. Sequential Bilateral Nephrectomy in a Rat Model Cystatin C Creatinine [mgl/l] [µmol/l] left right right left control nefrectomy Days after left nefrectomy Days after left nefrectomy Bökenkamp, Renal Failure 2001

19. Cystatin C and Creatinine after Kidney Transplantation Creatinine [µmol/l] Cystatin C [mgl/l] RTx mean ± SD Time after transplantation [days] Bökenkamp, Clin.Nephrol. 1999

20. Cystatin C in Transplanted vs Non-transplanted Patients Non-transplanted Transplanted 1 / Cystatine C (l/mg) Cin (ml/min • 1.73 m2) Bökenkamp et al, Clin.Chem.1999

21. Influence of Corticosteroids on Cystatin C Concentration 0.5 g Metpred + CyA + Aza < 10 mg Pred + CyA + Aza CyA + Aza CyA 3 x Methylpred. bolus 0.5 g: A - 17 dags prior (2 - 67) B before Methylprednisolone C + 3 days D + 8 days (6 - 11) Risch et al, Clin.Chem.2001

22. Steroid Therapy of Nephrotic Syndrome- Effect on GFR Markers - Serum-Albumin Cystatin C mg/l Legend „recurr“ = Recurrence „cont“ = Prednisone 60 mg/m2 • d „alt“ = Prednisone 45 mg/m2 • 48h „remiss“ = Remisson g/dl recurr. cont. alt. remiss. recurr. cont. alt. remiss. ml/min•1.73m2 Schwartz-GFR ß2-Microglobulin mg/l recurr. cont. alt. remiss. recurr. cont. alt. remiss. Bökenkamp et al, Clin. Chem. 2002

23. Prediction of ARF by Cystatin C- Study Design - Definition of ARF by creatinine-based RIFLE-criteria: „R“ = delta creat > 50% „I“ = delta creat > 100% „F“ = delta creat > 200% I day-2 I day 0 F day-2 F day 0 R day-2 R day 0 Herget-Rosenthal et al, KI 2004

24. Prediction of ARF- RIFLE-Criterium „R“ - Serum cystatin C Serum creatinine Creat: ANV * CysC: ANV * * * R- 3 R– 2 R– 1 R 0 R+1 Herget-Rosenthal et al, KI 2004

25. Prediction of ARF by Cystatin C Definition of ARF by creatinine-based RIFLE-criteria Herget-Rosenthal et al, KI 2004

26. 1000 100 10 mg/g creatinine 1 0.1 RRT+ RRT- RRT+ RRT- RRT+ RRT- RRT+ RRT- 0.01 Cystatin C Alpha1 NAG Liano-score Prediction of RRT by LMW-Proteinuria- Measurement ± 4 days prior to start RRT - • IC patients • Rapid rise in creatinine • ≥ 3 ARF criteria: • FENa >1%- Casts- Art. hypotension- Sepsis/SIRS- Rhabdomyolysis- Nephrotox. med = Cut-off Herget-Rosenthal et al, Clin Chem 2004

27. Incidence of Heart Failure in the Elderly- Based on GFR-markers ± 8 years before - Unadjusted incidence 5th quintiles: CysC > 1.26 mg/l Creat > 85 µmol/l f > 111µmol/l m MDRD < 58.6 ml/min Sarrnak et al, Ann.Intern. Med. 2005

28. Risk for Heart Failure in the Elderly- Based on GFR-markers ± 8 years before - Hazard ratios adjusted for age, sex, ethnic background and traditional cardiovascular risk factors. Sarnak et al, Ann.Intern. Med. 2005

29. All-cause Mortality in Elderly- Based on GFR-markers ± 8 years before - Annual mortality rate classified by serum creatinine and cystatin C quintiles Shlipak et al, NEJM 2005

30. But .... • No adjustment for Gold-standard GFR made in studies identifying cystatin C as risk factor for heart-disease • Does increase in cystatin C merely reflect mild renal insufficiency or a separate pathological mechanism? • Direct toxicity of cystatin C? • Low cystatin C levels in documented atherosclerosis/ aortic aneurysm! • No signs of disease in the cystatin C knock-out mouse!

31. Cystatin C in Diabetes mellitus Type 2 Rel. rise from upper reference value ROC-analysis Cystatin C Creatinine-blind range AUC Cys 0.954CG 0.873Creat 0.812 P < 0.05 Creatinine N = 52 adults; 51Cr-EDTA clearance; Cut-off 80 ml/min/1.73m2 Mussap et al, Kidney Int. 2002

32. Longitudinal Follow-up Diabetes Mellitus Type 2 Cystatin C Cockroft-Gault Within-individual residual SD: Ciothalamate 12.1% 100/Cys 9.0% 100/Creat 13.8% CG 14.2% MDRD 16.6% Creatinine MDRD Perkins et al, JASN 2005

33. Longitudinal Change in GFR in Diabetes mellitus Type 2 Perkins et al, JASN 2005

34. Cystatin C as a Marker of GFR • Facilitates assessment of renal function due to constant reference values. • Allows for estimation of GFR independent of body composition. • Allows for earlier detection of incipient acute renal failure. • Detects mild deterioration of GFR during follow-up. • Predicts heart failure / mortality (from CRF?) in the elderly.

35. When to Order Which Renal Function Test? • First consultation: => cystatin C + creatinine • Acute renal failure: => cystatin C (serum & urine) +/- creatinine • Follow-up chronic renal disease: => cystatin C (serum & urine) +/- creatinine • Quality of dialysis / indication for dialysis: => urea + creatinine • Kidney function in utero: => cystatin C + ß2-microglobulin (fetal serum / urine) • Altered metabolism with:- thyroid dysfunction- high-dose corticosteroids?

36. Questions?