BACKGROUND AND OBJECTIVE:
Monitoring of renal function in cystic fibrosis (CF) patients is essential. The dosage regimen of amikacin is regularly modified according to the patient's glomerular filtration rate (GFR). The aim of the study was to evaluate the use of
cystatin C (CyC) for monitoring amikacin therapy along with other markers of renal tubular and glomerular function, and damage [N-acetyl-beta-d glucosaminidase (NAG), creatinine level and creatinine clearance].
METHODS:
We compared the GFR, estimated from the serum concentrations of creatinine (Cockcroft-Gault formula) and cystatin C (CyC) (Grubb's formula). Seventy-one patients (mean age 12 years; range 4-28 years) with CF were treated by intermittent intravenous infusion of amikacin. Tubular nephrotoxicity was investigated by measurement of urine NAG/urine creatinine ratio (U-NAG/U-creatinine). Concentrations of all markers were measured before starting amikacin therapy and at days 3, 5, 7, 10 and 12. Fluorescence polarization analysis, turbidimetry, enzymatic phototometric creatinine deaminase method and fluorimetry were used for determination of serum amikacin, serum CyC, creatinine and urine NAG activity. Receiver operating characteristic (ROC) analysis was performed to assess the influence of GFR estimated from serum creatinine and serum CyC for the prediction of amikacin clearance during aminoglycoside therapy.
RESULTS:
Significant differences in the rate of U-NAG/U-creatinine were noted before and after treatment with amikacin (P < 0.001). Serum creatinine levels and creatinine clearance at the end of amikacin therapy (12th day) did not show any significant differences in comparison with the levels measured before the start of therapy (0th day). At days 5, 7, 10 and 12, serum CyC levels showed a significant elevation (P < 0.001), and cystatin C (CyC) clearance showed a significant decrease (P < 0.001) in comparison with the levels measured at day 0. The ratio of amikacin clearance/creatinine clearance decreased with therapy whereas the amikacin clearance/CyC and amikacin clearance/CyC clearance increased.
CONCLUSION: We showed that the rate of U-NAG/U-creatinine is a suitable marker for monitoring tubular nephrotoxicity in CF patients. Serum creatinine and estimated creatinine clearance are modest predictors of GFR in CF patients. cystatin C (CyC) appears to be a better marker of GFR than serum creatinine concentration or creatinine clearance in our study. Serum CyC levels and CyC clearance showed greater ability to predict amikacin clearance during therapy than creatinine clearance.
Showing posts with label glomerular filtration rate. Show all posts
Showing posts with label glomerular filtration rate. Show all posts
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Estimating GFR using serum cystatin C alone and in combination with serum creatinine: a pooled analysis of 3,418 individuals with CKD.
Serum cystatin C was proposed as a potential replacement for serum creatinine in glomerular filtration rate (GFR) estimation. We report the development and evaluation of GFR-estimating equations using serum cystatin C alone and serum cystatin C, serum creatinine, or both with demographic variables.
STUDY DESIGN: Test of diagnostic accuracy.
SETTING & PARTICIPANTS: Participants screened for 3 chronic kidney disease (CKD) studies in the United States (n = 2,980) and a clinical population in Paris, France (n = 438).
REFERENCE TEST: Measured GFR (mGFR).
INDEX TEST: Estimated GFR using the 4 new equations based on serum cystatin C alone, serum cystatin C, serum creatinine, or both with age, sex, and race. New equations were developed by using linear regression with log GFR as the outcome in two thirds of data from US studies. Internal validation was performed in the remaining one third of data from US CKD studies; external validation was performed in the Paris study.
MEASUREMENTS: GFR was measured by using urinary clearance of iodine-125-iothalamate in the US studies and chromium-51-EDTA in the Paris study. Serum cystatin C was measured by using Dade-Behring assay, standardized serum creatinine values were used.
RESULTS: Mean mGFR, serum creatinine, and serum cystatin C values were 48 mL/min/1.73 m(2) (5th to 95th percentile, 15 to 95), 2.1 mg/dL, and 1.8 mg/L, respectively. For the new equations, coefficients for age, sex, and race were significant in the equation with serum cystatin C, but 2- to 4-fold smaller than in the equation with serum creatinine. Measures of performance in new equations were consistent across the development and internal and external validation data sets. Percentages of estimated GFR within 30% of mGFR for equations based on serum cystatin C alone, serum cystatin C, serum creatinine, or both levels with age, sex, and race were 81%, 83%, 85%, and 89%, respectively. The equation using serum cystatin C level alone yields estimates with small biases in age, sex, and race subgroups, which are improved in equations including these variables.
LIMITATIONS: Study population composed mainly of patients with CKD.
CONCLUSIONS: Serum cystatin C level alone provides GFR estimates that are nearly as accurate as serum creatinine level adjusted for age, sex, and race, thus providing an alternative GFR estimate that is not linked to muscle mass. An equation including serum cystatin C level in combination with serum creatinine level, age, sex, and race provides the most accurate estimates.
STUDY DESIGN: Test of diagnostic accuracy.
SETTING & PARTICIPANTS: Participants screened for 3 chronic kidney disease (CKD) studies in the United States (n = 2,980) and a clinical population in Paris, France (n = 438).
REFERENCE TEST: Measured GFR (mGFR).
INDEX TEST: Estimated GFR using the 4 new equations based on serum cystatin C alone, serum cystatin C, serum creatinine, or both with age, sex, and race. New equations were developed by using linear regression with log GFR as the outcome in two thirds of data from US studies. Internal validation was performed in the remaining one third of data from US CKD studies; external validation was performed in the Paris study.
MEASUREMENTS: GFR was measured by using urinary clearance of iodine-125-iothalamate in the US studies and chromium-51-EDTA in the Paris study. Serum cystatin C was measured by using Dade-Behring assay, standardized serum creatinine values were used.
RESULTS: Mean mGFR, serum creatinine, and serum cystatin C values were 48 mL/min/1.73 m(2) (5th to 95th percentile, 15 to 95), 2.1 mg/dL, and 1.8 mg/L, respectively. For the new equations, coefficients for age, sex, and race were significant in the equation with serum cystatin C, but 2- to 4-fold smaller than in the equation with serum creatinine. Measures of performance in new equations were consistent across the development and internal and external validation data sets. Percentages of estimated GFR within 30% of mGFR for equations based on serum cystatin C alone, serum cystatin C, serum creatinine, or both levels with age, sex, and race were 81%, 83%, 85%, and 89%, respectively. The equation using serum cystatin C level alone yields estimates with small biases in age, sex, and race subgroups, which are improved in equations including these variables.
LIMITATIONS: Study population composed mainly of patients with CKD.
CONCLUSIONS: Serum cystatin C level alone provides GFR estimates that are nearly as accurate as serum creatinine level adjusted for age, sex, and race, thus providing an alternative GFR estimate that is not linked to muscle mass. An equation including serum cystatin C level in combination with serum creatinine level, age, sex, and race provides the most accurate estimates.
Cystatin C and other cardiovascular markers in hypertension
BACKGROUND AND OBJECTIVE: The aim of the study was to assess the relationship of cystatine C to other cardiovascular risk factors in hypertension .
PATIENTS AND METHOD: Cross-sectional study in hypertensive outpatients with normal creatinine values (< 1.6 mg/dl for males and < 1.4 mg/dl for women). Cystatin C was analyzed by immunonephelometry.
RESULTS: 283 patients (47% male) were evaluated. Cystatin C values were 0.65 (0.27) mg/l (median, intercuartile range, percentile 70 = 0.76 mg/l), and were correlated to the estimated glomerular filtration rate (GFR) (ml/min/1.73 m2), C reactive protein , and urinary albumin excretion (UAE). In multiple regression analysis the GFR was the most significant factor and explained 38% of cystatine C variability. GFR, (odds ratio [OR] = 5.84; 95% confidence interval [CI], 2.27-15.03; p < 0.001), age (OR = 1.05; 95% CI, 1.02-1.08; p < 0.001), and CRP (OR = 2.03; 95% CI, 1.07-3.84; p = 0.03), but not UAE >= 30 mg/24 h, were independent factors related to the presence of high levels (> 0.76 mg/l) of cystatine C in a logistic regression analysis. 58% of patients with UAE >= 30 mg/24h had cystatin C values < 0,76 mg/l.
CONCLUSIONS: In hypertensive patients, the GFR is the most important factor related to cystatine C values. Increased levels of cystatine C do not correspond to UAE augmentation.
Med Clin (Barc). 2008 Jan 19;130(1):1-5.Unidad de Hipertensión Arterial y Riesgo Vascular. Servicio de Medicina Interna. Hospital de Sagunto. Agencia Valenciana de Salud. Valencia. España
PATIENTS AND METHOD: Cross-sectional study in hypertensive outpatients with normal creatinine values (< 1.6 mg/dl for males and < 1.4 mg/dl for women). Cystatin C was analyzed by immunonephelometry.
RESULTS: 283 patients (47% male) were evaluated. Cystatin C values were 0.65 (0.27) mg/l (median, intercuartile range, percentile 70 = 0.76 mg/l), and were correlated to the estimated glomerular filtration rate (GFR) (ml/min/1.73 m2), C reactive protein , and urinary albumin excretion (UAE). In multiple regression analysis the GFR was the most significant factor and explained 38% of cystatine C variability. GFR, (odds ratio [OR] = 5.84; 95% confidence interval [CI], 2.27-15.03; p < 0.001), age (OR = 1.05; 95% CI, 1.02-1.08; p < 0.001), and CRP (OR = 2.03; 95% CI, 1.07-3.84; p = 0.03), but not UAE >= 30 mg/24 h, were independent factors related to the presence of high levels (> 0.76 mg/l) of cystatine C in a logistic regression analysis. 58% of patients with UAE >= 30 mg/24h had cystatin C values < 0,76 mg/l.
CONCLUSIONS: In hypertensive patients, the GFR is the most important factor related to cystatine C values. Increased levels of cystatine C do not correspond to UAE augmentation.
Med Clin (Barc). 2008 Jan 19;130(1):1-5.Unidad de Hipertensión Arterial y Riesgo Vascular. Servicio de Medicina Interna. Hospital de Sagunto. Agencia Valenciana de Salud. Valencia. España
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