Frans J Hoek1, Frits A W Kemperman, Raymond T Krediet. 1. Academic Medical Center, Department of Clinical Chemistry, Room F1-219, PO Box 22700, 1100 DE Amsterdam, The Netherlands. f.j.hoek@amc.uva.nl
Abstract
BACKGROUND: In clinical practice, the glomerular filtration rate (GFR) is often estimated from plasma creatinine. Several studies have shown cystatin C (cys C) to be a better parameter for the diagnosis of impaired renal function. No data are available, however, on the performance of cys C in follow-up of patients, compared with creatinine. Also, comparisons of cys C with the Cockcroft and Gault (C&G) formula for estimation of GFR are few. METHODS: Plasma samples were obtained from 93 consecutive patients seen for GFR determination and from 30 patients with diabetes mellitus type 2, of whom 23 were investigated a second time after 2 years. GFR was determined with [125I]iothalamate. Plasma creatinine was determined enzymatically and the creatinine clearance calculated according to C&G. Cys C was measured with a particle-enhanced immunonephelometric method. RESULTS: GFR correlated with 1/cys C (r = 0.873) as well as with C&G (r = 0.876). The area under the curve (AUC) of the receiver operating curves (ROCs), a measure of diagnostic accuracy, for cys C (0.931) and C&G (0.938) were equal (P = 0.815) and both better than the creatinine AUC (0.848; P = 0.006). Bland and Altman analysis showed that the simple formula GFR = -4.32 + 80.35 x 1/cys C, derived from our data, gave more accurate (P < 0.0001) and more precise (P = 0.024) GFR estimates than obtained with the C&G formula. The day-to-day variation (biological +analytical) for cys C was small (3.1%, SD 2.51%) in diabetic patients. In the follow-up study in diabetic patients, cys C was the parameter which had the best correlation (r = 0.66) with changes in GFR. CONCLUSIONS: Cys C shows a high correlation with GFR. With a very simple formula, cys C gives a good estimate of GFR, more accurate and precise than C&G. Because biological variation is low, cys C gives also a good assessment of GFR changes during follow-up. Cys C is the preferred endogenous parameter for GFR.
BACKGROUND: In clinical practice, the glomerular filtration rate (GFR) is often estimated from plasma creatinine. Several studies have shown cystatin C (cys C) to be a better parameter for the diagnosis of impaired renal function. No data are available, however, on the performance of cys C in follow-up of patients, compared with creatinine. Also, comparisons of cys C with the Cockcroft and Gault (C&G) formula for estimation of GFR are few. METHODS: Plasma samples were obtained from 93 consecutive patients seen for GFR determination and from 30 patients with diabetes mellitus type 2, of whom 23 were investigated a second time after 2 years. GFR was determined with [125I]iothalamate. Plasma creatinine was determined enzymatically and the creatinine clearance calculated according to C&G. Cys C was measured with a particle-enhanced immunonephelometric method. RESULTS: GFR correlated with 1/cys C (r = 0.873) as well as with C&G (r = 0.876). The area under the curve (AUC) of the receiver operating curves (ROCs), a measure of diagnostic accuracy, for cys C (0.931) and C&G (0.938) were equal (P = 0.815) and both better than the creatinine AUC (0.848; P = 0.006). Bland and Altman analysis showed that the simple formula GFR = -4.32 + 80.35 x 1/cys C, derived from our data, gave more accurate (P < 0.0001) and more precise (P = 0.024) GFR estimates than obtained with the C&G formula. The day-to-day variation (biological +analytical) for cys C was small (3.1%, SD 2.51%) in diabeticpatients. In the follow-up study in diabeticpatients, cys C was the parameter which had the best correlation (r = 0.66) with changes in GFR. CONCLUSIONS:Cys C shows a high correlation with GFR. With a very simple formula, cys C gives a good estimate of GFR, more accurate and precise than C&G. Because biological variation is low, cys C gives also a good assessment of GFR changes during follow-up. Cys C is the preferred endogenous parameter for GFR.
Authors: R J Macisaac; C Tsalamandris; M C Thomas; E Premaratne; S Panagiotopoulos; T J Smith; A Poon; M A Jenkins; S I Ratnaike; D A Power; G Jerums Journal: Diabetologia Date: 2006-05-03 Impact factor: 10.122
Authors: Clara Y Jones; Camille A Jones; Ira B Wilson; Tamsin A Knox; Andrew S Levey; Donna Spiegelman; Sherwood L Gorbach; Frederick Van Lente; Lesley A Stevens Journal: Am J Kidney Dis Date: 2008-05-02 Impact factor: 8.860
Authors: Andrea Z LaCroix; Jennifer S Lee; LieLing Wu; Jane A Cauley; Michael G Shlipak; Susan M Ott; John Robbins; J David Curb; Meryl Leboff; Douglas C Bauer; Rebecca D Jackson; Charles L Kooperberg; Steven R Cummings Journal: J Am Geriatr Soc Date: 2008-07-24 Impact factor: 5.562