Calculation of glomerular filtration rate based on cystatin C in cirrhotic patients.
BACKGROUND
Plasma creatinine and creatinine clearance are of limited value for the estimation of renal function in cirrhotics. In these patients, cystatin C (Cys C) has been proposed as an alternative marker of glomerular filtration rate (GFR) and Cys C-based equations for calculation of GFR have been developed in non-cirrhotic patient cohorts.


METHODS
We retrospectively analyzed correlation, bias, precision and accuracy of two Cys C-based formulae (Larsson and Hoek) for GFR estimation in comparison with two creatinine-based equations (Cockroft & Gault and MDRD). The Cys C was determined by an immunonephelometric method. The GFR was measured by means of inulin clearance in 44 consecutive patients with liver cirrhosis.


RESULTS
On average, inulin clearance was 28.3 (95% CI: 29.2-41.3 ml/min/1.73 m2). Creatinine as well as Cys C-based equations overestimated the true GFR by 105-154%. However, Cys C-based equations showed significantly lower bias and higher precision than the creatinine-based formulae. Correlation and accuracy tended to be better with the Hoek and Larsson equation than with the Cockroft & Gault or MDRD formulae. Hoek and Larsson equations showed a similar diagnostic performance in all statistical procedures.


CONCLUSIONS
Our data suggest a significant improvement of GFR estimation in liver cirrhotics by means of the Cys C-based Hoek and Larsson formulae. However, all estimates remain a crude approximation of true GFR and thus cannot replace gold standard methods.
Pöge
U
U
Department of Internal Medicine I, University of Bonn, Sigmund-Freud-Strasse 25, D 53105 Bonn, Germany. u.poege@uni-bonn.de
Gerhardt
T
T
Stoffel-Wagner
B
B
Klehr
H U
HU
Sauerbruch
T
T
Woitas
R P
RP
D003404:Creatinine / Q000097:blood / Q000652:urine; D055316:Cystatin C; D015891:Cystatins / Q000493:pharmacokinetics; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007444:Inulin / Q000097:blood / Q000652:urine; D008103:Liver Cirrhosis / Q000097:blood / Q000503:physiopathology* / Q000652:urine; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D011379:Prognosis; D011480:Protease Inhibitors / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012189:Retrospective Studies
C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D011480:Protease Inhibitors; D007444:Inulin; D003404:Creatinine