Estimating GFR in children with 99mTc‐DTPA renography: a comparison with single‐sample 51Cr‐EDTA clearance

Glomerular filtration rate (GFR) measurement by ⁵¹Cr‐ethylenediaminetetraacetic acid (EDTA) and blood sampling in children is usually cumbersome for the patient, parents and laboratory technicians. We have previously developed a method accurately estimating GFR in adults. The aim of the present study was to evaluate the accuracy of this non‐invasive method in children. We calculated GFR from ^99mTc‐diethylene triamine pentaacetic acid (DTPA) renography and compared with ⁵¹Cr‐EDTA plasma clearance of 29 children between the age of 1 month and 12 years (mean 4·7 years). The correlation between ^99mTc‐DTPA renography and ⁵¹Cr‐EDTA plasma clearance was for all children R = 0·96 (n = 29, P<0·0001), for children above 2 years of age R = 0·96 (n = 18, P<0·0001) and for children <2 years R = 0·84 (n = 11, P<0·001). We conclude that assessment of GFR from ^99mTc‐DTPA renography is reliable and comparable to GFR calculated from ⁵¹Cr‐EDTA plasma clearance. Because our method is non‐invasive and only takes 21 min, it may be preferable in many cases where an assessment of renal function is needed in children especially when renography is performed anyhow.     

The clearance concept with special reference to determination of glomerular filtration rate in patients with fluid retention

In subjects without fluid retention, the total plasma clearance of a renal filtration indicator (inulin, ^99mTc‐DTPA, ⁵¹Cr‐EDTA) is close to the urinary plasma clearance. Conversely, in patients with fluid retention (oedema, pleural effusions, ascites), there is a substantial discrepancy between the total plasma clearance and the urinary plasma clearance. This is owing to delayed indicator distribution to smaller or larger parts of the interstitial space, which in patients with ascites may simulate a peritoneal dialysator. In patients with fluid retention, urinary plasma clearance should be assessed to obtain a correct measurement of the glomerular filtration rate (GFR). In theory, total plasma clearance with late samples (24‐h, 48‐h) may be applied in patients with fluid retention, but validation hereof has not been performed. Until such studies are completed, it is recommended that patients with fluid retention have their GFR measured by a urinary plasma clearance technique with controlled quantitative urinary sampling within a few hours after indicator injection.     

Gamma‐variate plasma clearance versus urinary plasma clearance of 51Cr‐EDTA in patients with cirrhosis with and without fluid retention

In patients with fluid retention, the plasma clearance of ⁵¹Cr‐EDTA (Cl_exp obtained by multiexponential fit) may overestimate the glomerular filtration rate (GFR). The present study was undertaken to compare a gamma‐variate plasma clearance (Cl_gv) with the urinary plasma clearance of ⁵¹Cr‐EDTA (Cl_u) in patients with cirrhosis with and without fluid retention. A total of 81 patients with cirrhosis (22 without fluid retention, 59 with ascites) received a quantitative intravenous injection of ⁵¹Cr‐EDTA followed by plasma and quantitative urinary samples for 5 h. Cl_gv was determined from the injected dose relative to the plasma concentration‐time area, obtained by a gamma‐variate iterative fit. Cl_exp and Cl_u were determined by standard technique. In patients without fluid retention, Cl_gv, Cl_exp and Cl_u were closely similar. The difference between Cl_gv and Cl_u (Cl_gv – Cl_u = ΔCl) was mean ?0·6 ml min^?1 1·73 m^?2. In patients with ascites, ΔCl was significantly higher (11·8 ml min^?1 1·73 m^?2, P<0·0001), but this value was lower than Cl_exp – Cl_u (17·5 mL min^?1 1·73 m^?2, P<0·01). ΔCl increased with lower values of GFR (P<0·001). In conclusion, in patients with fluid retention and ascites Cl_gv and Cl_exp overestimates GFR substantially, but the overestimation is smaller with Cl_gv. Although Cl_u may underestimate GFR slightly, patients with ascites should collect urine quantitatively to obtain a reliable measurement of GFR.     

Prediction of post‐operative glomerular filtration rate after nephrectomy for renal malignancy

The importance of a correct estimation of contralateral renal function in cases of renal malignancy is obvious, necessitating a conservative approach to tumour resection when function of the contralateral kidney is markedly reduced. The aim of the present study was to determine the accuracy of preoperative gamma camera renography and ⁵¹Cr‐EDTA clearance to predict the glomerular filtration rate (GFR) early and up to 6 months after nephrectomy for renal malignancy. Patients (n=40) underwent both gamma camera renography (^99mTC‐DTPA) and ⁵¹Cr‐EDTA clearance preoperatively, whereas ⁵¹Cr‐EDTA clearance was measured within 1 week and up to 6 months after nephrectomy. The single kidney GFR values of the contralateral kidneys were estimated preoperatively and then compared with the post‐operative ⁵¹Cr‐EDTA clearance values. The predicted GFR values were lower compared with the measured post‐operative ⁵¹Cr‐EDTA clearance values (45 ± 2 vs. 54 ± 3 ml min^–1 1 week after nephrectomy and 53 ± 3 ml min^–1 6 months later, P<0·01, respectively). The difference between the measured and predicted GFR was larger in patients below the median age of 60 years (P<0·05) and confined to patients with a relative uptake of >30% by the tumour affected kidney. Prediction of post‐operative GFR by non‐invasive renal function tests performed prior to surgery for renal malignancy underestimate post‐operative GFR when the function of the tumour affected kidney is preserved, indicating an adaptive GFR increase in these cases.     

肾小球滤过率智能检测分析系统的研制及临床应用研究

目的 研制肾小球滤过率(GFR)智能检测分析系统(GFRBMAS),并探讨其检测GFR的临床应用价值.方法 采用VB 6.0软件编程,并配置好GFRBMAS.采用99锝m-二:乙烯三胺五乙酸(99Tcm-DTPA)清除率准确测定79例不同疾病住院患者GFR(Tc-GFR),检测并比较GFRBMAS与日立7170S全自动生化仪所测得的血清肌酐(SCr)、尿素氮(BUN)、血尿酸(Uric)、血清钙(Ca)和血清磷(P)值,同时以GFRBMAS、Robert公式测定或测算GFR(GFRBMAS-GFR、Robert-GFR),以Cockcroft/Gault公式计算内生肌酐清除率(CG-CCr),所得数据进行相关分析与对比研究.结果 两种检测方法测得的SCr、BUN、Uric、Ca、P值差异均无统计学意义(P均＞0.05),且两者均呈显著正相关(P均＜0.01).肾功能正常组和不全组Robert-GFR、CG-CCr值均明显小于Tc-GFR值,差异有统计学意义(P均＜0.01),而GFRBMAS-GFR值与Tc-GFR值相近.相关分析显示,肾功能不全组及正常组GFRBMAS-GFR、Robert-GFR、CG-CCr与Tc-GFR值均呈显著正相关,与SCr、BUN均呈负相关(P＜0.05或P＜0.01).结论 GFRBMAS-GFR、Robert-GFR、CG-CCr均能在一定程度上准确反映GFR,而GFRBMAS-GFR可代替Tc-GFR应用于临床.     

Reliability of the MDRD method for estimating glomerular filtration rate in relation to gender, body mass index and extracellular fluid volume

Background The accuracy of estimating glomerular filtration rate from plasma creatinine (eGFR) has been questioned but it is unclear how much covert error in several reference methods that have been used has contributed to this perceived inaccuracy. The aim of the study was to evaluate eGFR in comparison with a second ‘gold standard’ to test the performance of the primary gold standard and to examine the influence of patient demographics (age, body mass index (BMI), extracellular fluid volume (ECV) and gender). Design Non‐fasting multisample GFR and ECV were measured in 80 subjects simultaneously and independently with Cr‐51‐EDTA (GFR_EDTA) and iohexol (GFR_iohexol). Percentage bias and imprecision in the prediction of, and disagreement with, GFR_EDTA were compared between eGFR and GFR_iohexol. Another simplified method for measuring GFR, the slope‐only method (^SOGFR), was also evaluated against multisample GFR (measured with the opposing indicator). Accuracies were assessed in all subjects and across age, BMI and ECV boundaries of 65 y, 29 kg m^?2 and 14 L. Results eGFR was less precise than GFR_iohexol (imprecisions of 22·3% and 12·9%; P < 0·01). The precision of ^SOGFR was intermediate between eGFR and GFR_iohexol. Both GFR_iohexol and eGFR were less precise in the elderly, the obese and men, but minimally influenced by ECV. ^SOGFR was minimally influenced by subject demographics. Conclusion Although eGFR does not predict GFR (based on a primary gold standard) as accurately as a second gold standard, a significant component of its poor performance is the result of inaccuracy in the primary gold standard. ^SOGFR measured with Cr‐51‐EDTA is superior to eGFR.     

Selection of Routine Method for Determination of Glomerular Filtration Rate in Adult Patients

The precision and reproducibility of three different clearance methods as used in clinical routine assessment of glomerular filtration rate (GFR) were investigated in 51 patients: total [51Cr]EDTA plasma clearance (E); 24-hr endogenous creatinine clearance (C); and creatinine clearance estimated from the plasma creatinine concentration, weight, and sex-and age-dependent mean creatinine excretion rate (c). The precision and reproducibility (coefficient of variation) for single determinations were, in patients with E ≥ 30 ml/min, 5.5 and 4.1% (E); 26.9% (C); and 23.2 and 11.0% (c). The corresponding figures for E < 30 ml/min were 11.6 and 11.5% (E); 21.9% (C); and 21.4 and 6.5% (c). The precision of C could not be ameliorated by excluding single deviating determinations, but only by excluding patients for whom the precision of 15.5% for mean of three determinations of C (total material) could be reduced to 10% by excluding 25% of the patients. The present data indicate that E in most cases is the method of choice for assessment of GFR in clinical routine work. For changes in renal function, especially at low functional levels, c may be of value.     

One-sample determination of glomerular filtration rate (GFR) in children. An evaluation based on 75 consecutive patients

Abstract

Background and aim. From a clinical point of view determination of glomerular filtration rate (clearance) is important. The aim of the present study was to compare the one-sample clearance to reference multiple-sample ⁵¹Cr-EDTA clearance in consecutively referred children suspected of or with established nephro-urological disorders. Material and methods. A total of 75 children, age ½–13 years, received a quantitative intravenous injection of ⁵¹Cr-EDTA followed by six plasma samples 10–120 min after injection. The multiple-sample clearance was measured as injected dose relative to the area under the plasma radioactivity curve. The one-sample clearance was determined from a single plasma sample collected at 60, 90 or 120 min after injection according to the one-pool method. Results. The overall accuracy of one-sample clearance was excellent with mean numeric difference to the reference value of 0.7–1.7 mL/min. In 64 children, the one-sample clearance was within ± 4 mL/min of the multiple-sample value. However, in 11 children the numeric difference exceeded 4 mL/min (4.4–19.5). Analysis of age, body size, distribution volume, indicator retention time, clearance level, curve fitting, and sampling time could not explain the observed large difference between one-sample and multiple-sample clearance in these 15% of the children. Conclusion. In the majority of children there is an excellent agreement between one-sample clearance and multiple-sample clearance. However, unexpectedly in a small fraction (15%) larger discrepancies are found. If an accurate clearance value is essential a multiple-sample determination should be performed.     

计算法测定肾小球滤过率的临床应用价值

目的 :探讨采用 WCP公式计算方法测定肾小球滤过率 (GFR)的临床应用价值。方法 :采用 99m Tc DTPA清除率测定 6 6例不同疾病住院患者 GFR(Tc GFR) ,并测血清肌酐 (SCr)及尿素氮 (BU N) ,同时以 WCP公式、Robert公式计算 GFR(WCP GFR,Robert GFR) ,以 Cockcroft/ Gault公式计算内生肌酐清除率 (CG CCr) ,所得数据进行对比研究及相关性分析。结果 :除肾功能正常者 CG CCr与 BU N无显著相关外 ,肾功能不全及肾功能正常者的 WCP GFR、Robert GFR、CG CCr均分别与 Tc GFR呈显著正相关(P均 <0 .0 1) ,与 BU N、SCr呈显著负相关 (P<0 .0 1或 P<0 .0 5 ) ;与 Robert GFR、CG CCr比较 ,WCPGFR始终与 Tc GFR最接近 (P均 >0 .0 5 ) ;WCP GFR、Robert GFR、CG CCr与 Tc GFR的平均差绝对值逐渐增大 ,三者间差异显著 (P均 <0 .0 5 )。结论 :WCP GFR、Robert GFR、CG CCr均能在一定程度上准确反映 GFR,而以 WCP GFR更准确 ,且简便、快速、安全而廉价 ,可代替 Tc GFR应用于临床     

Arterio-venous concentration difference of [51Cr]EDTA after a single injection in man. Significance of renal function and local blood flow

Summary. The present investigation was undertaken in order to study (1) the difference in arterial (C_a) and venous (C_v) concentration of [⁵¹Cr]EDTA (ethylenediaminetetra-acetate) after a single intravenous injection, (2) the impact of different physiological variables on this difference, and (3) the error introduced in the measurement of renal plasma clearance and total plasma clearance by using venous blood samples instead of arterial. In 13 patients with GFR ranging from 29 to 150 ml min^-1, C_a was higher than C_v immediately after the injection. After mean 38 min (range 12–82 min) the two curves crossed, and 180–300 min post-injection (p.i.) C_v was 5·9% higher than C_a (range 0·5–13·9%, P<0·001). The more reduced renal function, the smaller was the concentration difference. The areas under the arterial and the venous plasma concentration curves did not differ significantly at either 0–∞ or 0–300 min p.i., whereas the venous area 0–100 min p.i. underestimated the arterial area in the same period by 4·1% (P<0·05). In a computer simulation model, variation in the forearm capillary permeability–surface area product did not have any significant influence on the C_v–C_a difference, whereas the difference was very sensitive to even small changes in forearm blood flow within the physiological range. For measurement of renal plasma clearance it is recommended to use one long period: from the time of injection until 300 min p.i. or longer. If the clearance period is too short, the use of venous samples will overestimate the true renal clearance. Plasma clearance determined by venous and arterial blood samples does not differ significantly as long as the concentration is followed from the time of injection and a long period is applied. When simplified plasma clearance techniques are used, different results may be obtained from venous and arterial samples. The simplified techniques using venous blood samples—which usually include some empirical corrections—should be sufficiently reliable in daily clinical practice provided the forearm blood flow is reasonably high, e.g. exposure to cold should be avoided.     

Total plasma clearance versus urinary plasma clearance of 51Cr-EDTA in patients with cirrhosis with and without fluid retention

Abstract

Background and aim. In patients with fluid retention, the total plasma clearance of ⁵¹Cr-EDTA (Cl_P) may overestimate the glomerular filtration rate (GFR). The present study was therefore undertaken in order to compare Cl_P with the urinary plasma clearance of ⁵¹Cr-EDTA (Cl_U) in patients with cirrhosis with and without fluid retention. Material and methods. A total of 136 patients with cirrhosis (24 without fluid retention, 112 with ascites) received a quantitative intravenous injection of ⁵¹Cr-EDTA followed by plasma and quantitative urinary samples for 5 hours. Cl_P was determined from the injected dose relative to the plasma concentration-time area, extrapolated to infinity. Cl_U was determined as urinary excretion relative to the plasma concentration-time area up to voiding. Results. In patients without fluid retention, the difference between Cl_P and Cl_U (Cl_P ? Cl_U = Cl_Δ) was mean 4.5 mL/min/1.73 m². In patients with ascites, Cl_Δ was significantly higher (17.6 mL/min/1.73 m², p < 0.0001). Cl_Δ increased with lower values of GFR (r = ? 0.458, p < 0.001). Repeated measurements of Cl_U in a subgroup of patients with fluid retention (n = 25) gave almost identical values. Different types of corrections of one-pool clearance were almost identical with Cl_P, except for higher clearance values, which were somewhat underestimated by the former. Conclusion. In patients with fluid retention and ascites Cl_P and corrected one-pool clearance overestimates GFR substantially. Although Cl_U may underestimate GFR slightly, patients with ascites should collect urine quantitatively in order to obtain a reliable measurement of GFR.     

Clinical benefits of using inulin clearance and cystatin C for determining glomerular filtration rate in HIV-1-infected individuals treated with dolutegravir

Introduction

Dolutegravir may inhibit creatinine transporters in renal tubules and elevate serum creatinine levels. We investigated the usefulness of glomerular filtration rate (GFR) measured using inulin clearance (Cin), creatinine clearance (Ccr), and estimated GFR based on both serum creatinine (eGFRcre) and serum cystatin C (eGFRcys).

Clinical value of serum cystatin C by ELISA for estimation of glomerular filtration rate

The search for whether endogenous markers of changes in glomerular filtration rate (GFR) by serum cystatin C assay and serum cystatin C compare with creatinine clearance by the Cockeroft-Gault formula and the evaluation of its clinical significance as a marker of GFR is important in clinical practice at present. Serum cystatin C was determined by sandwich enzyme immunoassay using a kit. Control blood samples were collected from 70 healthy subjects and 168 patients with various kidney diseases. Creatinine clearance (Cockeroft-Gault formula) as a measure of GFR, in 168 patients with various kidney diseases, depends on the creatinine clearance; GFR parameters were used to divide patients into two groups. The GFR was >80 mL/min in 38 patients (group A) and <80 mL/min in 130 patients (group B). The two groups were analyzed by correlation coefficient and diagnostic sensitivity and specificity were assessed by the receiver-operating characteristic (ROC) plots (area under the curve). Of the 70 healthy control individuals, the serum level of cystatin C was measured as normal value range and a reference interval of 1.05+/-0.18 micro g/mL (mean+/-1.96 SD, 95% confidence limits for the upper references limit is 1.4 microg/mL). In group A, serum cystatin C had no correlation to the creatinine clearance (r=0.171, P>0.05) and in group B, serum cystatin C was closely correlated to the creatinine clearance (r=-0.771, P<0.001). Diagnostic sensitivity and specificity were assessed by the ROC plots for serum cystatin C (area under the curve=0.8461, SE=0.057) and creatinine clearance (area under the curve=0.7642, SE=0.068). These data suggest that combined measurement of serum cystatin C is useful to estimate GFR, especially to detect the reduction of GFR. Further studies are required to evaluate the whether serum cystatin C as a more sensitive marker of early renal injury might be extremely useful, particularly in nonproteinuric or unapparent renal disease.     

与肾小球滤过率相关的临床因素探讨

目的：探讨肾小球滤过率（GFR）与多种临床因素的相关关系。方法：用^99mTc-DTPA清除率测定46例肾功能正常组和52例肾功能不全组患者的GFR，同时采血测血清肌酐（SCr）、尿素氮（BUN）、尿酸、钾、钠、钙、血红蛋白，并测心率、尿质量比、24h尿蛋白定量、平均动态压、体重指数、体表面积，记录测试者年龄，测定GFR所用同位素剂量。将各组及不同原发病的GFR分别与同组的上述各临床因素进行简单相关分析，对与GFR有显著相关关系的上述临床因素再与GFR进行多元相关分析。结果：在肾功能正常、肾功能不全及不同原发病者中，除例数较少的病种外，其GFR始终与SCr呈显著负相关，而与其他临床因素的相关关系则不相同。结论：在多种原发病引起的肾功能不全及肾功能正常者中，SCr是反映GFR的理想指标。     

Reassessment of a classical single injection 51Cr‐EDTA clearance method for determination of renal function in children and adults. Part I: Analytically correct relationship between total and one‐pool clearance

Background. Total plasma clearance of ⁵¹Cr‐EDTA, Cl, is widely used as a measure of GFR. Commonly, only the final part of the plasma concentration curve is measured, and a one‐pool clearance (slope‐intercept clearance), Cl₁, is computed. Empirically determined second‐order polynomials of the general form Cl = b?Cl₁+c?Cl₁² are usually used to estimate Cl from a measured Cl₁. However, theoretical considerations indicate that such corrections underestimate Cl at high values. Aims. To derive an analytically correct relationship between Cl and Cl₁ and determine the parameters involved for children and adults. Material and methods. Cl was determined in 149 subjects (M/F/children: 71/46/32) from a complete plasma concentration curve followed for 4–5?h after injection of ⁵¹Cr‐EDTA (range of clearance: 8–183?mL/min/1.73?m²). Plasma volume, PV and the “missing” area under the plasma fraction curve, a (minutes), not used for determination of Cl₁, were measured. Results. The true relationship between Cl and Cl₁ is given by Cl = Cl₁/(1+f?Cl₁), where f = a/PV. For men, women and children alike, the equation f = 0.0032?BSA^?1.3 was applicable (BSA = body surface area in m²). Estimation errors on clearance were within ±8?% for adults and ±13?% for children (95?% limits of agreement). Conclusions. The true relationship between Cl and Cl₁ of ⁵¹Cr‐EDTA is given, resulting in a common correction equation applicable for children and adults. The new equation has better mathematical behaviour than quadratic equations on very high values of clearance and takes into account dependence on body size.     

Reassessment of a classical single injection 51Cr‐EDTA clearance method for determination of renal function in children and adults. Part II: Empirically determined relationships between total and one‐pool clearance

Background. The one‐pool or slope‐intercept technique is widely used when determining total ⁵¹Cr‐EDTA plasma clearance (Cl). The one‐pool clearance (Cl₁), which always exceeds Cl, has mostly been corrected to Cl by multiplication by a constant factor = 0.80, suggested by Chantler (CH_0.80), or by using a second‐order polynomial originally proposed by Brøchner‐Mortensen (BM) and later recommended by the British Nuclear Medicine Society (BM_BNMS). Theoretical considerations indicate that the CH correction gives a systematic overestimate of Cl, whereas the BM correction may underestimate Cl at high values. Objective. To assess the accuracy of Cl as estimated from Cl₁ corrected either by CH_0.80 or by second‐order polynomials. Material and methods. Cl_ref was determined in 149 subjects (M/F/children: 71/46/32) from a complete plasma curve followed for 4–5?h after injection of ⁵¹Cr‐EDTA (range of Cl_ref: 8–183?mL/min/1.73?m²). Cl_est was determined from Cl₁ subsequently corrected by CH_0.80 and four second‐order polynomials. Results. Using CH_0.80 correction, Cl_est underestimated Cl_ref (by a maximum of 20?%) at Cl_ref values less than about 100?mL/min/1.73?m² in children and 130?mL/min/1.73?m² in adults. At higher clearance levels, Cl_ref was increasingly overestimated. Taking the BM_BNMS correction as representative of second‐order polynomials, Cl_est increasingly underestimated Cl_ref at high levels, the error being 10?% at a Cl_ref value of about 175?mL/min/1.73?m². Conclusions. We suggest that the tested correction equations are replaced by the given common correction equation based on the “true” relationship between Cl₁ and Cl thoroughly described in part I of this study.     

数字化智能检测分析系统测定肾小球滤过率的临床研究

目的 探讨数字化智能检测分析系统(B&G系统)测定肾小球滤过率(GFR)的临床应用价值.方法 采用99锝-二乙烯三胺五乙酸(99mTc-DTPA)清除率准确测定216例不同疾病非透析治疗住院患者的GFR(Tc-GFR),同时检测血清肌酐(SCr)及尿素氮(BUN);并用B&G系统、Robert公式分别测定GFR (B&G-GFR、Robert-GFR),用Cockcroft/Gault公式计算内生肌酐清除率后换算GFR(CG-CCr-GFR),对所得数据进行对比研究及相关分析.结果 216例患者中,肾功能不全组(106例)和肾功能正常组(110例)患者B&G-GFR与Tc-GFR比较差异均无统计学意义(ml·min-1·1.73 m-2:29.13±18.96比32.28±25.03、121.13±49.79比118.48±43.25,均P>0.05),而Robert-GFR(ml·min-1·1.73 m-2:21.45±15.67、93.54±30.01)、CG-CCr-GFR(ml·min-1·1.73 m-2:11.87±8.69、86.27±21.44)均明显低于Tc-GFR (P<0.05或P<0.01).肾功能不全组B&G-GFR、Robert-GFR、CG-CCr-GFR与Tc-GFR差值绝对值(ml·min-1·1.73 m-2:6.15±14.07、13.83±11.36、23.41±24.34)均明显低于肾功能正常组(7.65±6.54、24.94±13.24、32.21±21.81,均P<0.05).两组B&G-GFR、Robert-GFR、CG-CCr-GFR与Tc-GFR 均呈正相关(P<0.05或P<0.01),与SCr均呈负相关(P<0.05或P＜0.01).结论 B&G-GFR、RobertGFR、CG-CCr-GFR均能在一定程度上准确反映GFR,而以B&G-GFR更准确,可代替Tc-GFR应用于临床.B&G系统较其他GFR检测方法具有更准确、简便、快速、安全而廉价的优势,值得临床推广应用.

Abstract：

Objective To discuss the clinical application value of determining glomerular filtration rate (GFR)with the new intelligent determination and analysis system for GFR(B&G System).Methods GFR of 216 hospitalized patients suffering from the different diseases was determined accurately by clearance rate of 99mTc-diethylene triamine pentoacetic acid(99mTc-DTPA)(Tc-GFR),and the serum creatinine(SCr)and blood urea nitrogen(BUN)were also determined.At the same time GFR was determined by B&G system and Robert formula(B&G-GFR,Robert-GFR),and creatinine clearance rate(CCr)and GFR were calculated by Cockcroft/Gault formula(CG-CCr-GFR).All the results were compared,and correlation analysis was done for the three groups of data.Results Among 216 patients,B&G-GFR and Tc-GFR in 106 patients with renal insufficiency and 110 patients with normal renal function showed no significant (P<0.05 or P<0.01).The values of B&G-GFR,Robert-GFR,CG-CCr-GFR and Tc-GFR in renal 13.24,32.21±21.8l,all P<0.05).B&G-GFR,Robert-GFR,and CG-CCr-GFR of both groups were positively correlated with Tc-GFR(P<0.05 or P<0.01),but negatively correlated with SCr(P<0.05 or P<0.01).Conclusion B&G-GFR,Robert-GFR and CG-CCr-GFR,to a certain extent,do accuratelyreflect GFR.However,B&G-GFR is more accurate than others,and it can take the place of Tc-GFR clinically.B&G system has the advantage of accuracy,simplicity,speed,safety and low-price compared with other methods for the determination of GFR,and it warrants popularization.     

Serum cystatin C level for better assessment of glomerular filtration rate in cystic fibrosis patients treated by amikacin

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‐β‐ d glucosaminidase (NAG), creatinine level and creatinine clearance]. Methods: We compared the GFR, estimated from the serum concentrations of creatinine (Cockcroft–Gault formula) and 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 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. 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.     

A simple chemical method for the quantification of the contrast agent iohexol,applicable to glomerular filtration rate measurements

We present a method for the quantification of the contrast agent iohexol in serum. Iohexol is deiodinated by alkaline hydrolysis and the released iodine subsequently measured according to the eerie arsenite method. The assay requires 50 u.1 of serum and has a high capacity as it involves few analytical steps. The high precision (2% CV) and sensitivity make the method applicable to the recently developed procedure for the determination of glomerular filtration rate, which is based on the assessment of the clearance of iohexol from serum. The method is simple and rapid and requires no expensive equipment.     

造影剂剂量与估计肾小球滤过率比值对高龄糖尿病患者造影剂肾病的诊断价值

目的探讨经皮冠状动脉介入治疗(PCI)术后造影剂肾病(CIN)的发病情况;评估造影剂剂量(CMV)与估计肾小球滤过率(eGFR)比值对高龄糖尿病患者造影剂肾病的诊断价值。 方法回顾性分析875例在济宁医学院附属医院心内科接受PCI患者的临床资料。采用SPSS19.0统计软件进行统计学分析,比较CIN组与非CIN组患者的各项资料,如性别、年龄、吸烟、是否低血压、左室射血分数(LVEF)、血红蛋白值、低密度脂蛋白(LDL-C)、空腹血糖、高血压和2型糖尿病病史;术前血肌酐(Scr)、eGFR;术后48hScr、eGFR。用Logistic回归分析CIN的危险因素。 结果入组患者CIN患病率4.80%(42例),男性、合并高血压病、2型糖尿病、高脂血症、吸烟、低血压、贫血、发病时心肌梗死合并休克的患病率分别为65.71%、54.86%、37.26%、22.51%、34.17%、16.80%、4.20%、8.91%。CIN与非CIN患者相比,在高龄患者(33.33%,19.33%,χ²＝4.902,P<0.05)、患有糖尿病(52.38%,36.49%,χ²＝4.317,P<0.05),吸烟(50.00%,33.37%,χ²＝4.914,P<0.05),发病时低血压(28.57%,16.21%,χ²＝4.374,P<0.05),心肌梗死伴休克(19.05%,8.40%,χ²＝5.579,P<0.05),低LVEF[(36.46±9.27)%,(43.62±3.46)%,t＝2.398,P<0.05]及造影剂用量大[(154.5±95.3)mL,(115.04±49.63)mL,t＝2.069,P<0.05]的患者更容易发生CIN;eGFR在CIN组明显降低[(72.50±15.06)mL/(min·1.73m²),(108.55±21.7)mL/(min·1.73m²),t＝7.220,P<0.05]。CMV/eGFR在CIN组与非CIN组间[(2.19±1.30),(1.01±0.40),t＝ －3.439,P<0.05]差异有统计学意义。多因素回归分析显示高龄(年龄≥70岁,RR＝5.27,P<0.05)、糖尿病(RR＝9.87,P<0.05)、LVEF(RR＝7.35,P<0.05)、术前eGFR(RR＝4.12,P<0.05)、心肌梗死合并休克(RR＝6.75,P<0.05)、CMV/eGFR(RR＝13.45,P<0.05)是CIN的危险因素。ROC工作曲线显示,CMV/eGFR>1.52对于高龄糖尿病患者是否发生CIN的敏感度为72.50%,特异度为84.00%。 结论PCI前评估患者的危险因素非常重要,高龄糖尿病更容易发生CIN;CMV/eGFR比值是一个独立的能够预测高龄糖尿病患者PCI后能否发生CIN的指标。