S O'Riordan1, E Ouldred, S Brice, S H D Jackson, C G Swift. 1. Clinical Age Research Unit, Department of Healthcare of the Elderly, Guys, Kings and St Thomas' School of Medicine, Denmark Hill Campus, Kings College London, London SE5 9PJ. oriordanlamb@ukonline.co.uk
Abstract
AIMS: To assess whether cystatin C, a new serum marker of renal function, is a better index of creatinine or digoxin clearance than serum creatinine in older people. METHODS: Twenty-two volunteers over the age of 65 years (mean 73 +/- 5) were recruited from a healthy elderly volunteer database. None of the volunteers was taking digoxin or other medication known to interfere with digoxin kinetics or assay. Digoxin was infused at a dose of 7-10 microg kg(-1) and blood samples were taken over the following 48 h and assayed for serum digoxin. Serum cystatin C, creatinine and creatinine clearance were measured and a calculated creatinine clearance was estimated using the Cockcroft Gault formula. Digoxin clearance was calculated using a pharmacokinetic software package. All values were log transformed to normalize their distribution. RESULTS: Of the 22 volunteers enrolled into the study, 18 completed the study. Serum cystatin C ranged between 0.72 and 1.89 mg l(-1) and serum creatinine ranged from 69.6 to 153.9 micromol l(-1). Measured creatinine clearance ranged from 38 to 123 ml min(-1) and calculated creatinine clearance from 29.5 to 88.0 ml min(-1). Digoxin clearance ranged from 51.0 to 103.5 ml min(-1). Cystatin C correlated extremely well with creatinine (r=0.93, P<0.001, 95% CI 0.82, 0.97) and with creatinine clearance (r=0.67, P=0.002, 95% CI 0.3, 0.87). Neither serum cystatin C nor serum creatinine correlated with digoxin clearance (r=0.25, P=0.31, 95% CI -0.25, 0.64 and r=0.44, P=0.068, 95% CI -0.03, 0.75, respectively). Measured creatinine clearance, however, did correlate well with digoxin clearance (r=0.55, P=0.018, 95% CI 0.11, 0.81). CONCLUSIONS: Serum cystatin C and serum creatinine show very similar correlations with creatinine and digoxin clearances. Serum cystatin C does not offer any advantages in this respect. It remains to be seen whether cystatin C offers any advantage over creatinine in elderly people in other respects.
AIMS: To assess whether cystatin C, a new serum marker of renal function, is a better index of creatinine or digoxin clearance than serum creatinine in older people. METHODS: Twenty-two volunteers over the age of 65 years (mean 73 +/- 5) were recruited from a healthy elderly volunteer database. None of the volunteers was taking digoxin or other medication known to interfere with digoxin kinetics or assay. Digoxin was infused at a dose of 7-10 microg kg(-1) and blood samples were taken over the following 48 h and assayed for serum digoxin. Serum cystatin C, creatinine and creatinine clearance were measured and a calculated creatinine clearance was estimated using the Cockcroft Gault formula. Digoxin clearance was calculated using a pharmacokinetic software package. All values were log transformed to normalize their distribution. RESULTS: Of the 22 volunteers enrolled into the study, 18 completed the study. Serum cystatin C ranged between 0.72 and 1.89 mg l(-1) and serum creatinine ranged from 69.6 to 153.9 micromol l(-1). Measured creatinine clearance ranged from 38 to 123 ml min(-1) and calculated creatinine clearance from 29.5 to 88.0 ml min(-1). Digoxin clearance ranged from 51.0 to 103.5 ml min(-1). Cystatin C correlated extremely well with creatinine (r=0.93, P<0.001, 95% CI 0.82, 0.97) and with creatinine clearance (r=0.67, P=0.002, 95% CI 0.3, 0.87). Neither serum cystatin C nor serum creatinine correlated with digoxin clearance (r=0.25, P=0.31, 95% CI -0.25, 0.64 and r=0.44, P=0.068, 95% CI -0.03, 0.75, respectively). Measured creatinine clearance, however, did correlate well with digoxin clearance (r=0.55, P=0.018, 95% CI 0.11, 0.81). CONCLUSIONS: Serum cystatin C and serum creatinine show very similar correlations with creatinine and digoxin clearances. Serum cystatin C does not offer any advantages in this respect. It remains to be seen whether cystatin C offers any advantage over creatinine in elderly people in other respects.
Authors: M Plebani; R Dall'Amico; M Mussap; G Montini; N Ruzzante; R Marsilio; G Giordano; G Zacchello Journal: Ren Fail Date: 1998-03 Impact factor: 2.606
Authors: J Kyhse-Andersen; C Schmidt; G Nordin; B Andersson; P Nilsson-Ehle; V Lindström; A Grubb Journal: Clin Chem Date: 1994-10 Impact factor: 8.327