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Background: Proteinuria is a risk factor for end-stage renal disease (ESRD). Creatinine clearance (CrCl) is usually used as a marker to monitor the progression of ESRD, while cystatin C (CYST) has also been considered as a marker of renal function. Tumor-associated trypsin inhibitor (TATI) has been shown to be a promising marker of renal function. The aim of this study was to examine the relationship between CrCl, CYST, ß(2)-microglobulin (B2M) and TATI, with glomerular filtration rate (GFR) in patients with different levels of proteinuria., Methods: Seventy-one patients (37 males, 34 females, mean age 53 ± 15 years) were included in the study. GFR was measured by the bladder cumulative method using (99m)Tc-DTPA. Blood levels of CYST, B2M and TATI were also measured. CrCl and proteinuria were determined by 24-hour urine collection. Statistical analysis was performed with multivariate analysis., Results: The results are expressed as the ratio to GFR of CrCl and reciprocals of CYST (100/CYST), B2M (100/B2M) and TATI (100/TATI). The ratio CrCl/GFR increased from 1.41 in patients with proteinuria <1 g/day, to 1.66 (p<0.05) in those with proteinuria >3 g/day. The ratio 100/CYST/GFR was 1.67 and 2.28 (p<0.05), 100/B2M/GFR 0.90 and 0.69 and 100/TATI/GFR 0.14 and 0.19, respectively. Multivariate analysis demonstrated that ClCr/GFR as well as 100/CYST/GFR was independently related to the degree of proteinuria., Conclusions: CrCl and CYST overestimate GFR in patients with heavy proteinuria, while the ratios 100/TATI and 100/B2M with GFR do not significantly change. The direct measurement of GFR still remains the best method to assess the progression of renal damage in patients with heavy proteinuria.

Introduction: Beta 2 microglobulin (beta2M) is filtered by the glomeruli and reabsorbed by the proximal tubular cells where it is metabolized. Its plasma concentration increases with decreasing renal function., Aim: To compare serum creatinine (Cr) and serum beta2M as markers of GFR., Patients and Methods: In 160 adult patients, with various kidney diseases and different GFR, serum Cr (autoanalyzer), serum beta2M (RIA) and GFR (bladder cumulative method using 99mTc-DTPA as glomerular tracer) were measured in the same day., Results: A linear relationship was observed between In GFR and both In serum Cr (lnCr=3.112-0.716 lnGFR; r=0.92) and ln serum beta2M (lnbeta2M= 4.274-0.814 lnGFR; r = 0.90). With decreasing GFR the increase in serum beta2M was higher than that of serum Cr (see regression coefficients that are significantly different). The normal upper limit of serum Cr corresponds to a GFR 48.1 mL/min while that of serum beta2M to a GFR 65.0. With decreasing GFR the increase of serum beta2M occurs before than that of serum Cr., Conclusions: With declining renal function, serum beta2M increases more and before than serum Cr. Serum beta2M is a good endogenous marker of GFR, better than serum Cr.

The aim of this study was to evaluate the possibility of predicting creatinine clearance (CCr) from plasma creatinine (PCr) and body com-position analysis by means of electrical impedance, thereby avoiding urine collection. Fat-free mass (FFM) and body cell mass (BCM) were measured in 50 renal patients (M29, F21; aged 17-74 years; mean 52.6) with different degrees of renal function (PCr 0.8-9.0 mg/dL, mean 2.13) by using a tetrapolar impedance plethysmograph. The relationship between 24 h-urinary creatinine excretion (UCr) and FFM and BCM was evaluated in 20 of the above reported patients (MI I, F9; PCr 0.8-9.0 mg/dL, mean 2.27). The mean ratio of 24 h UCr/FFM was 25.6 mg/kg in males and 22.5 in females and that of 24 h UCr/BCM was 51.9 mg/kg in males and 48.1 in females. CCr was estimated in the remaining 30 patients (M18, F12; PCr 0.9-8.8 mg/dL, mean 2.04) from individual FFM and BCM values and PCr. In the same patients CCr was predicted also according to the Cockcroft and Gault formula and, for comparison, was measured with the conventional method by collecting 24 h urine, CCr predicted from the values of FFM and BCM gave a good estimate of 24 h CCr, more precise than that of Cockcroft and Gault CCR. Also, the repeatability of the predicted CCr was clearly better than that of 24 h CCr. In conclusion, creatinine clearance can be predicted, avoiding urine collection, from plasma creatinine and body composition analysis by means of electrical impedance.

The aim of this study was to evaluate the agreement between the glomerular filtration rate (GFR) and an estimate of creatinine clearance (CCr), calculated from the values of body cell mass (BCM) and of plasma creatinine (PCr), thus avoiding urine collection. The value of BCM was obtained from the measurement of total body impedance in 80 renal patients. The relationship between 24-hour urinary creatinine excretion and BCM was evaluated in 30 of these patients. Body cell mass CCr (ml/min) was then calculated in each of the remaining 50 patients. For comparison, 24-hour CCr was measured in the same patients. The correlation coefficient of BCM CCr with GFR was 0.961, while that of 24-hour CCr with GFR was 0.869. Also, the agreement with GFR was better for BCM CCr than for 24-hour CCr. In conclusion, creatinine clearance predicted from body cell mass and plasma creatinine is a better indicator of renal function than measured 24-hour creatinine clearance.

The aim of this study is to evaluate the effects of contrast media on both tubular and glomerular function. Different parameters of tubular and glomerular function were determined before and at 1, 3, and 5 days after the intravascular administration of contrast media in 100 adult renal patients (plasma creatinine 0.6-10.8 mg/dL, mean: 1.3). Urinary activities of five tubular enzymes (alanine aminopeptidase, gamma-glutamyltransferase, alkaline phosphatase, lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase) increased significantly on the first day after the administration of contrast media, indicating a tubular damage. Glomerular filtration rate and the conventional tests of glomerular function (plasma creatinine, creatinine clearance, and urinary proteins) presented only slight variations after the administration of contrast media. In conclusion, contrast media principally affected the renal tubule (as demonstrated by enzymuria), while their effects on glomerular function were very mild.