Serum cystatin C for the prediction of glomerular filtration rate with regard to the dose adjustment of amikacin, gentamicin, tobramycin, and vancomycin

Dosage regimes of aminoglycosides and vancomycin are modified according to the glomerular filtration rate (GFR). In 130 hospitalized patients who were administered amikacin, gentamicin, tobramycin, and vancomycin by intermittent intravenous infusion, we compared the predicted GFR values from the serum concentrations of creatinine (Cockcroft and Gault. Nephron. 1976;16:31-41) and cystatin C (Larsson et al. Scand J Clin Lab Invest. 2004;64:25-30) with respect to their relevance for proper dosage. In 83% and 67% of the cases, respectively, the serum levels of albumin and cholinesterase were below the corresponding lower limit of the reference range. The ratio of creatinine/cystatin C concentrations presented significant correlations with the predicted rate of creatinine production (r=0.762, P<0.001), serum albumin concentration (r=0.205, P<0.05), and catalytic serum concentrations of cholinesterase (r=0.207, P<0.05), gamma glutamyltransferase (r=-0.273, P<0.01), and alkaline phosphatase (r=-0.289, P<0.01). The GFR (mean+/-SD; median) predicted by the serum creatinine (84.0+/-35.1 mL/min/1.73 m; 82.6 mL/min/1.73 m) was significantly higher (P<0.001) than that predicted by the serum cystatin C (53.1+/-30.2 mL/min/1.73 m; 44.9 mL/min/1.73 m). The ratio between the GFR values predicted by creatinine and cystatin C had a highly significant negative correlation with the rate of creatinine production (r=-0.912, P<0.001). Furthermore, significant differences were found for the peak concentrations and clearances of amikacin and vancomycin estimated by means of the Abbottbase Pharmacokinetic Systems program, and using the GFR values predicted by the serum creatinine and cystatin C (P<0.005). In patients with hepatic dysfunction, the clearance of creatinine predicted by the Cockcroft-Gault formula leads to a significant overestimation of the GFR. Cystatin C seems to be a valid alternative as a GFR marker with regard to drug dose adjustment in these cases.     

Estimation of the initial dose setting of vancomycin therapy with use of cystatin C as a new marker of renal function

In recent years, it has been suggested that the glomerular filtration rate (GFR) can be predicted on the basis of serum cystatin C concentrations and that this measurement is more sensitive than serum creatinine concentration as a marker of renal function. In this study, to investigate the clinical utility of the initial dose setting of vancomycin by the population mean method with use of serum cystatin C as a marker of renal function, we compared the correlations between measured vancomycin concentrations and predicted vancomycin concentrations based on serum cystatin C or serum creatinine concentrations in elderly (>/=65 years old) and nonelderly (<65 years old) patients. An analysis of prediction accuracy (bias) and precision was evaluated by calculating the mean prediction error (ME), the mean absolute error (MAE), and the root mean squared prediction error (RMSE). For nonelderly patients (n = 50), there was no significant difference in the MAE based on the use of serum creatinine or serum cystatin C concentration. However, for elderly patients (n = 105), the MAE based on serum cystatin C concentration was significantly better than that based on serum creatinine level. These results suggest that serum cystatin C is a good marker of renal function in comparison with serum creatinine for dose setting of vancomycin, especially in an elderly population.     

Validation of estimated renal function measurements compared with the isotopic glomerular filtration rate in an HIV-infected cohort

We performed a cross-sectional study to determine the best method for estimating the glomerular filtration rate (GFR) in HIV-infected subjects. Isotopic GFR was correlated with 24-h urine creatinine clearance, cystatin C levels, and 3 creatinine-based equations-the Modification of Diet in Renal Disease (MDRD), Cockcroft-Gault (CG), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)-in 15 patients. Cystatin C showed the strongest correlation with isotopic GFR (r=-0.760, p=0.001). When cystatin C was used as the reference variable for all 106 patients, CKD-EPI proved to be superior to the other equations (r=-0.671, p<0.001). Time with HIV infection, unsuppressed viral load, low CD4 T-cell counts, and use of protease inhibitors are related to an increased risk of renal impairment, leading us to recommend early initiation of antiretroviral therapy accompanied by a regular renal study.     

A nonradioactive iothalamate method for measuring glomerular filtration rate and its use to study the renal handling of cibenzoline

A high-pressure liquid chromatographic method was developed to measure nonradioactive iothalamate in serum and urine for use in estimating glomerular filtration rate (GFR). This method was used to study the renal handling of cibenzoline, an experimental antiarrhythmic drug. The mean cibenzoline clearance was 3.5 +/- 2.5 (SD) times the glomerular filtration rate. The clearance of non-protein-bound cibenzoline was seven times GFR, indicating excretion by the renal tubular secretory pathway for organic bases. This drug, at the doses used, did not lower creatinine clearance, indicating that the effect of basic drugs competing with creatinine for the base secretory pathway appears to be dose and drug dependent.     

87例肾脏疾病患者血清Cystatin C与肌酐测定评价分析

目的：评价血清半胱氨酸蛋白酶抑制剂-C（Cystatin C）对肾脏损害患者肾小球滤过功能的临床应用价值。方法：采用胶乳增强免疫透射比浊法分别测定49例正常人和87例肾病患者血清Cystatin C浓度，同时测定血清肌酐（Scr）及内生肌酐清除率（Ccr），将血清Cystatin C与Scr和Ccr相比较。结果：Cystatin C水平随内生肌酐清除率下降逐渐升高。在不同肾病组Cystatin C的阳性检出率与Scr和Ccr的阳性检出率相比差异有显著性（P〈0．01）。Ccr〉80ml／min肾病患者有55％显示Cystatin C异常。结论：Cystatin C比Scr更能够反应肾脏滤过功能的损害。可替代内生肌酐清除率作为判断肾小球滤过功能的指标。     

Serum cystatin C is not a better marker of creatinine or digoxin clearance than serum creatinine

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.     

血清胱蛋白酶抑制剂C测定对评价小儿肾功能的临床意义

目的：探讨在肾脏疾病中检测血清胱蛋白酶抑制剂C（Cystatin C,Cys C）浓度评价小儿肾小球滤过率（GFR）的价值。方法：用ELISA法测定65例肾脏病患儿血清Cys C浓度，同时每例患儿均测定血清肌酐（Scr）、血尿素氮（BUN），计算24h肌酐清除率（Ccr），依据Ccr结果将患儿分为4组，分别比较肾功能降低各组与肾功能正常组血清Cv。C、BUN及Scr的结果，并分析血清Cysc、BUN、Scr与Ccr的相关性。结果：在肾功能不全代偿期患儿中血清Cys C与肾功能正常组比较差异有统计学意义（P〈0.01），而Scr、BUN与肾功能正常组比较差异无统计学意义（P〉0．05）。血清Cys C、Scr、BUN与Ccr均呈显著负相关。结论：临床上用检测血清Cys C浓度来评价肾小球滤过功能的准确性优于Scr、BUN，尤其对早期肾功能损害更加敏感，其方法简单、快捷、便于临床推广。     

四组不同程度肾损害患者血清胱抑素C水平检测结果分析

目的通过检测血清胱抑素(CysC)水平,探讨其在肾功能损害及肾损伤早期诊断中的应用价值。方法对150例不同程度肾脏疾病患者按肾小球滤过率(eGFR)的不同分成四组观察组,100例体检健康者为正常对照组,用颗粒加强散射免疫比浊法测定胱抑素C水平,同时检测血清肌酐(Scr)、尿素氮(Bun)、尿肌酐(Ucr)并计算出eGFR。结果随着eGFR的下降,胱抑素测定值分别是(1.25±0.16)mg/L、(1.51±0.19)mg/L、(2.52±0.21)mg/L、(5.18±0.23)mg/L。差异有统计学意义,同时在肾小球滤过率大于50mL/min时,只有胱抑素升高。结论血清胱抑素C是反映肾功能损伤的敏感指标,在临床应用上,优于尿素氮、肌酐和内生肌酐清除率的检测,同时与肾病患者病程发展呈正相关。     

脓毒症并发急性肾损伤患者 RAAS 水平与 GFR 的关系

目的：探讨脓毒症并发急性肾损伤（AKI）患者肾素—血管紧张素—醛固酮系统（RAAS）、胱抑素 C （cystatin C,Cys C）水平与肾小球滤过率（GFR）的关系。方法测定 ICU 脓毒症 AKI 患者的 RAAS 水平、血清肌酐（serum creatinine,SCr）与 Cys C 水平,并评估 GFR,分析各指标间的相关性。结果 Cys C、肾素、血管紧张素 I 浓度与 GFR 呈负相关;Cys C 和血清肌酐正相关。结论脓毒症 AKI 患者 Cys C 是 GFR 的内源性标志物,RAAS 水平可能影响 GFR。     

Pharmacokinetics of ciprofloxacin in elderly subjects

The pharmacokinetics of single-dose oral ciprofloxacin 500 mg was ascertained in 12 elderly and 12 young subjects. Mean age of the elderly volunteers was 75.4 years and the mean measured creatinine clearance in this group was 40.7 ml/min. Serum and saliva were collected in serial order for 24 hours (elderly) and 10 hours (young), and assayed for ciprofloxacin by high-performance liquid chromatography. The geriatric subjects had higher serum levels throughout the sampling period, with a peak level of 3.24 +/- 0.79 versus 2.26 +/- 0.75 micrograms/ml for the younger group (p less than 0.005; one-way analysis of variance). A twofold increase in the ciprofloxacin half-life may be partly explained by a decrease in the glomerular filtration rate, as shown by slower ciprofloxacin renal clearance (152.4 +/- 54.2 vs 395.6 +/- 139.0 for elderly and young subjects respectively; p less than 0.001). We concluded that in elderly patients, ciprofloxacin should be administered at an interval not less than every 12 hours to prevent accumulation and eventually toxicity.     

Effect of rofecoxib on the glomerular filtration rate, proteinuria and the renin-angiotensin-aldosterone system in elderly subjects with chronic renal impairment

Considering the increasing popularity and prescribing of specific COX-2 inhibitors, a new class of NSAIDs lacking gastrointestinal side effects, the evaluation of their effects on renal function has become very important. OBJECTIVE: The aim of the study was to evaluate the effect of rofecoxib on GFR, proteinuria and the renin-angiotensin-aldosterone system (RAAS) in elderly patients with chronic renal impairment under controlled conditions of water and salt intake. SUBJECTS: There were ten patients (average age 67 years, range 53 - 80 years) with analgesic or vascular nephropathy (average GFR 54 ml/min/1.73 m2, range 30 - 79 ml/min/ 1.73 m2) given 25 mg rofecoxib daily for seven days under balanced conditions of water and sodium metabolism (salt intake 6 - 8 g/24 hours). METHODS: The effect of rofecoxib on GFR measured using inulin clearance (C(in)), creatinine clearance (C(Cr)) serum cystatin C concentration (S(cystatin)), tubular creatinine secretion (using the ratio C(Cr)/C(in)), 24-hour urinary excretion of albumin (U(alb)V) and prostaglandins (U(PGE2)V and U(PGF2alpha)V), basal and stimulated plasma renin activity (PRA) and serum aldosterone concentration S(aldosterone) was evaluated before and on Day 7 during rofecoxib treatment. RESULTS: Rofecoxib did not significantly change C(in), C(Cr), S(cystatin), C(Cr)/C(in) and U(alb)V. However, U(PGE2)V and U(PGF2alpha)V were decreased during rofecoxib administration (p = 0.059 and p = 0.024, respectively). Rofecoxib attenuated the stimulated rise of PRA and S(aldosterone) (p = 0.019 and p = 0.008, respectively). CONCLUSIONS: Short-term rofecoxib administration was not associated with significant change in GFR in elderly patients with moderate chronic renal impairment under conditions of balanced salt and water metabolism despite significant attenuation of RAAS activity. Since the C(Cr)/C(in) ratio did not change in our study, we assume rofecoxib to have no influence on creatinine tubular secretion.     

Serum levels of beta-trace protein and glomerular filtration rate--preliminary results

The aim of this study was to evaluate the relationship between serum levels of beta-trace protein (BTP), a low molecular weight (MW) protein, and glomerular filtration rate (GFR). GFR and serum levels of BTP, and for comparison creatinine (Creat), cystatin C (Cys) and beta 2-microglobulin (beta 2M), were measured in 60 patients, with renal function ranging from normality to advanced renal failure. Serum levels of BTP progressively increased with the reduction of GFR. A good correlation was found between GFR and serum levels of BTP (r=0.918), Creat (r=0.932), Cys (r=0.937), and beta 2M (r=0.924). Furthermore, no statistically significant difference was found between BTP and Creat, Cys, beta 2M, as indicators of a moderate GFR impairment. These preliminary data indicate that BTP might be suitable as an indicator of GFR.     

Cystatin-C对早期慢性肾脏病诊断的临床意义

目的：同时检测血清胱抑素C（Cystatin-C/CyC）与血清肌酐（SCr）、血尿素氮（BUN）,并计算肾小球滤过率（GFR）,各指标间互相比较,探讨CyC在慢性肾脏病患者肾功能评估中的早期诊断价值。方法：选择在肾脏内科住院的131例慢性肾脏病（CKD）患者作为研究对象,并以40例体检健康者作为对照,根据GFR分组,选择CyC、SCr、BUN与GFR作为观察指标,通过SPSS13.0软件计算,分析CyC在CKD早期诊断中的临床意义。结果：CyC在各组间均有统计学意义（P〈0.05）,相关分析CyC、SCr、BUN与GFR相比,CyC相关系数最高。结论：CyC可作为评价GFR的敏感指标,与SCr、BUN相比能更早、更客观的反映肾小球滤过功能。     

肝硬化并发肾功能损害患者血清胱抑素C与肾功能指标相关性分析

目的 探讨肝硬化并发肾功能损害检测血清胱抑素C（Cys-C）与肾功能相关指标间的相关性.方法 129例肝硬化患者根据测得的肾小球滤过功能（GFR）作为评价肾功能的金指标,将患者分为A（肝硬化肾功能正常组）、B（肝硬化并发肾功能不全组）、C（肝硬化继发肾功能衰竭组）三组,比较三组患者Cys-C浓度的差异,并与血清肌酐（Scr）、血β2微球类蛋白（β2-MG）、血肌酐清除率（Ccr）检测相比较.结果 CysC、Scr、β2-MG、Ccr等指标均随着A、B、C三组患者肾功能损害严重程度呈现升高或降低（t=6.65、6.85、6.58、4.54,均P＜0.05）;Cys-C、Scr、Ccr、β2-MG等指标异常检出率：A组为31.1％、11.1％、8.9％、26.7％,B组为83.7％、30.2％、34.9％、46.5％,C组为100.0％、85.4％、87.8％、95.1％.结论 血清Cys-C检测是评价肾小球滤过功能的一个灵敏标志物,对肝硬化并发肾功能损害的早期诊断具有临床指导意义.     

计算法与应用99mTc-DTPA清除率测定肾小球滤过率的临床对比研究

目的 评价临床应用计算法测定肾小球滤过率（GFR）的准确性。方法 用^99mTc-DTPA清除率测定60例不同疾病住院病人GFR（Tc-GFR)，并测血清肌酐，同时以WCP公司测定GFR（WCP-GFR),以Cockcroft/Gault公式计算内生肌酐清除率（CG－CCr)。肾功能不全及正常组WCP－GFR、CG－GFR分别与Tc-GFR进行相关分析，比较两组WCP－GFR、CG－GFR与Tc-GFR间显著性差异以及WCP－GFR、Tc-GFR间平均差和CG－GFR、Tc-GFR间平均差的显著性差异。结果 WCP－GFR及CG－CCr均可在一定程度上准确反映GFR，而以WCP－GFR数值更接近Tc-GFR，准确性更高，临床上可代替Tc-GFR。结论 WCP－GFR是一种准确、简便、快捷测定GFR方法。     

Pharmacokinetics in renally impaired subjects of NXY-059, a nitrone-based,free-radical trapping agent developed for the treatment of acute stroke

OBJECTIVE: NXY-059 is a nitrone-based, free-radical trapping agent being developed for the treatment of acute ischaemic stroke. Elimination of NXY-059 is primarily renal. The objective of the study was to investigate the pharmacokinetics of NXY-059 in subjects with renal impairment. METHODS: Twenty-four subjects with a glomerular filtration rate (GFR) ranging from 19 ml/min to 100 ml/min received NXY-059 intravenously over a 24-h period. Drug in plasma and urine was measured for 72 h. One-hour loading infusion rates were proportional to body weight, while maintenance infusion rates were proportional to GFR. Target plasma levels were 60 micro mol/l for subjects with mild (GFR 50-100 ml/min) and moderate (GFR 30-49 ml/min) renal impairment, and 30 micro mol/l for subjects with severe renal impairment (GFR <30 ml/min). GFR was measured as sinistrin clearance. RESULTS: The data indicated no tolerability or safety concerns with NXY-059. The half-life, which normally is approximately 2-4 h, was in the order of 10-12 h in subjects with moderate and severe renal impairment. The distribution parameters steady-state volume of distribution (V(ss)) and unbound fraction in plasma at 13-15 l and 0.53-0.58, respectively, were virtually the same as previously observed in healthy subjects. Plasma clearance of NXY-059, which ranged from 9 ml/min to 76 ml/min, was directly proportional to kidney function (GFR) with no discernible contribution by non-renal clearance. The correlation coefficient squared (r(2)) was 0.93, both when the renal function parameter was GFR and when it was creatinine clearance estimated from serum creatinine, age, weight and sex. CONCLUSION: Non-renal elimination of NXY-059 appeared to be insignificant even in subjects with low renal capacity. Patients with renal impairment should have their dose of NXY-059 adjusted for renal function, conveniently assessed from serum creatinine.     

Renal tubular injury is present in acute inflammatory bowel disease prior to the introduction of drug therapy

BACKGROUND: 5-aminosalicylic acid (5-ASA) has been associated with renal complications in inflammatory bowel disease. Renal function is typically monitored using serum creatinine; however, significant disease may predate increases in creatinine. AIMS: To identify whether markers of early renal disease (urinary albumin, alpha-1-microglobulin [alpha-1-M] and N-acetyl-beta-D-glucosaminidase [NAG], and serum cystatin C) are useful in the assessment of renal function in inflammatory bowel disease patients receiving 5-ASA. METHODS: Twenty-one patients with a new diagnosis of inflammatory bowel disease were investigated. Samples were taken at diagnosis, and at 3-monthly intervals after the commencement of 5-ASA, for 1 year. RESULTS: Mean creatinine clearance was 100 mL/min and did not change following treatment. Inflammatory bowel disease was not associated with albuminuria. Urinary N-acetyl-beta-D-glucosaminidase and alpha-1-microglobulin at diagnosis were increased in 10 (48%) and 11 (52%) patients, respectively: treatment was not associated with consistent changes in urinary protein excretion. There was a significant correlation between cystatin C and creatinine clearance both at diagnosis (r=-0.533, P=0.0275) and combining the initial and follow-up data (r=-0.601, P < 0.01), but not between creatinine and creatinine clearance (P > 0.05). CONCLUSIONS: Tubular proteinuria is an extra-intestinal manifestation of inflammatory bowel disease irrespective of 5-ASA treatment. Tubular proteins are not useful predictors of an adverse renal response to 5-ASA. Serum cystatin C may be an improved marker of glomerular filtration rate in this setting.     

Review article: renal function assessment in cirrhosis - difficulties and alternative measurements

BACKGROUND: Renal function in patients with cirrhosis is important prognostically, both before and following liver transplantation. Its prognostic impact is reflected by the inclusion of serum creatinine in the model for end-stage liver disease score, which is now used for recipient prioritization on liver transplantation waiting lists in the USA. AIM: To review the accuracy of the surrogate markers for the assessment of renal function, i.e. glomerular filtration rate, particularly in patients with cirrhosis. METHOD: We reviewed the available literature in PubMed regarding the markers for GFR evaluation and the factors which affect their accuracy in cirrhosis. RESULTS: Although creatinine is widely available, it is an unreliable marker of glomerular filtration rate, particularly in patients with cirrhosis. Clearance of exogenous markers is considered the 'gold standard', but this methodology has many drawbacks, particularly poor applicability. Several mathematical formulae for estimated glomerular filtration rate are used to overcome some of these limitations: Cockcroft-Gault and Modification of Diet in Renal Disease formulae are the most frequently applied, but they are based on serum creatinine. CONCLUSIONS: Due to the inaccuracy of serum creatinine and its derived formulae in estimating glomerular filtration rate, alternative serum markers, such as cystatin C, and new formulae are desirable. These need formal evaluation in patients with cirrhosis so as to have a reliable surrogate of glomerular filtration rate, and to obviate many problems that are associated with using creatinine and estimated glomerular filtration rate.     

Serum beta2-microglobulin in the assessment of renal function.

This study was undertaken to compare the serum beta2-microglobulin (beta2-m) as a test of renal function with the plasm creatinine and the glomerular filtration rate as estimated by the 24 hour endogenous creatinine clearance and the single injection 51Cr EDTA clearance method. Of the 33 patients with a variety of renal diseases and the four healthy volunteers studied, an excellent correlation was found between the serum beta2-m concentration (measured by radioimmunoassay) and the plasma creatinine, the creatinine clearance and the 51Cr EDTA clearance. When a more simple and less expensive method becomes available for the measurement of serum beta2-m it could prove a useful test of renal function. The assay of beta2-m in the urine could prove valuable for assessing whether proteinuria is glomerular or tubular in origin.     

Predicting the glomerular filtration rate from serum creatinine, serum cystatin C and the Cockcroft and Gault formula with regard to drug dosage adjustment

OBJECTIVES: To compare the accuracy of the classification of the degree of decrease in glomerular filtration rate (GFR), measured exactly (as inulin clearance) on the basis of serum concentrations of creatinine (Scr), cystatin C (Scyst) and creatinine clearance predicted according to Cockcroft and Gault (CG), and to establish whether any of the above methods is more accurate than the other 2. SUBJECTS: The study was conducted in 126 patients (52 men, 74 women) aged 18 to 64 years with various chronic renal diseases (predominantly various forms of glomerulonephritis and tubulointerstitial nephritis). The study subjects were divided into 3 subgroups according to GFR levels. Subgroup A (n = 41) included individuals with GFR >50 ml/min/1.73 m2, subgroup B (n = 56) was made up by individuals with GFR of 20-50 ml/min/1.73 m2, while subgroup C (n = 29) comprised individuals with GFR <20 ml/min/1.73 m2. METHODS: GFR was determined on the basis of renal inulin clearance (Cin) under conditions of stable plasma levels and water loading. Each individual had his/her Scr, Scyst values measured and CG was calculated. Results were evaluated using discrimination analysis. RESULTS: Mean values and SD of the monitored markers in the subgroups were as follows. Subgroup A: Scr 102.4 (38.3) micromol/l, Scyst 1.46 (0.42) mg/l, CG 80.0 (19.2) ml/min/1.73 m2. Subgroup B: Scr 161.2 (45.6) micromol/l, Scyst 2.01 (0.55) mg/l, CG 46.1 (16.7) ml/min/1.73 m2. Subgroup C: Scr 314.9 (58.3) micromol/l, Scyst 3.41 (0.96) mg/l, CG 24.8 (7.6) ml/min/1.73 m2. The percent of correct classifications and the respective confidence intervals (95%) for the methods used were as follows. Subgroup A: Scr 79.3 (64.6, 94.0), Scyst 75.9 (60.3, 91.5), CG 86.2 (73.6, 98.8). Subgroup B: Scr 51.8 (35.5, 68.1), Scyst 57.1 (41.5, 72.7), CG 64.3 (48.6, 80.0). Subgroup C: Scr 90.2 (81.0, 99.2), Scyst 80.5 (68.1, 92.9), CG 87.8 (77.8, 97.8). The percent of correct classifications established on the basis of Scr, Scyst and CG in subgroup B is significantly lower than that of correct classifications in subgroups A and C (p < 0.05-0.001). The percent of correct classifications using Scr, Scyst and CG, estimated separately for each subgroup (A, B, C) does not differ significantly. CONCLUSIONS: The findings support the assumption that estimation of the decrease in GFR using Scr, Scyst and CG is, as regards their utilization in everyday practice, suitable for individuals with severely decreased GFR (<20 ml/min/1.73 m2) and for individuals with a decrease in GFR to levels >50 ml/min/173 m2. Estimation of the decrease in GFR using the above subgroups did not demonstrate significant differences among Scr, Scyst and CG. Using the above markers, estimation of the decrease in GFR is the least reliable with GFR values in the range of 20-50 ml/min/1.73 m2.