What Is the Most Appropriate Formula to Use in Estimating Glomerular Filtration Rate in Adult Arabs without Kidney Disease?

Cystatin C-based equations for estimating glomerular filtration rate do not require race or sex coefficients

Estimation or measurement of glomerular filtration rate (GFR) is generally required for optimal treatment of patients. Plasma creatinine has been used for estimation of GFR since 1926 and plasma cystatin C since 1979. The creatinine level is strongly dependent upon muscle mass and as the average muscle mass of different populations may vary, creatinine-based GFR-estimating equations have since 1999 used more than 10 different race coefficients to improve the diagnostic performance of such equations. But 'race' cannot be determined by biological measurements and is thus an ill-defined biological entity and controversial as it involves self-reporting and social considerations. In contrast, cystatin C-levels are virtually independent of muscular mass and cystatin C-based GFR-estimating equations do not require race coefficients for reliable estimation of GFR. The use of cystatin C-based GFR-estimating equations, alone or in conjunction with creatinine-based GFR-estimating equations, is therefore highly recommended to eliminate the use of race coefficients in estimating GFR. Although sex is a more biology-oriented parameter than race, sex terms may in some cases be controversial, involving self-reporting and social considerations. However, sex terms are not required for adequate estimation of GFR using cystatin C-based equations.

Vitamin D3 reduces risk of cardiovascular and liver diseases by lowering homocysteine levels: double-blinded, randomised, placebo-controlled trial

The objective of this study was to evaluate the effect of vitamin D3 on total homocysteine (tHcy) and C-reactive protein (CRP) levels and liver and kidney function tests in overweight women with vitamin D deficiency. Therefore, a randomised, double-blind placebo, controlled clinical trial was conducted on 100 eligible women. Subjects were randomly divided into two groups: the placebo (n 50) and the vitamin D (n 50) which received 1250 µg vitamin D3 per week for 2 months. The participants' 25-hydroxyvitamin D (25(OH)D), tHcy, CRP, alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine and estimated glomerular filtration rate (eGFR) were measured and compared before and after treatment. Results showed that the tHcy, CRP, AST, ALT and eGFR levels after the 2nd month of vitamin D3 intervention were significantly (P < 0·001) decreased and the 25(OH)D, urea and creatinine levels were significantly (P < 0·001) increased in the treatment group. In the placebo group, no significant changes were identified throughout the follow-up period. In conclusion, vitamin D3 intervention with a treatment dose of 1250 µg/week for at least 2 months may help in lowering Hcy and CRP levels and may improve liver function tests, which in turn might help in minimising the risk of CVD and liver diseases among overweight women but negatively affect kidney function.

Ultra-High-Precision, in-vivo Pharmacokinetic Measurements Highlight the Need for and a Route Toward More Highly Personalized Medicine

Clinical drug dosing would, ideally, be informed by high-precision, patient-specific data on drug metabolism. The direct determination of patient-specific drug pharmacokinetics ("peaks and troughs"), however, currently relies on cumbersome, laboratory-based approaches that require hours to days to return pharmacokinetic estimates based on only one or two plasma drug measurements. In response clinicians often base dosing on age, body mass, pharmacogenetic markers, or other indirect estimators of pharmacokinetics despite the relatively low accuracy of these approaches. Here, in contrast, we explore the use of indwelling electrochemical aptamer-based (E-AB) sensors as a means of measuring pharmacokinetics rapidly and with high precision using a rat animal model. Specifically, measuring the disposition kinetics of the drug tobramycin in Sprague-Dawley rats we demonstrate the seconds resolved, real-time measurement of plasma drug levels accompanied by measurement validation via HPLC-MS on ex vivo samples. The resultant data illustrate the significant pharmacokinetic variability of this drug even when dosing is adjusted using body weight or body surface area, two widely used pharmacokinetic predictors for this important class of antibiotics, highlighting the need for improved methods of determining its pharmacokinetics.

Computed Tomographic Estimation of Relationship between Renal Volume and Body Weight of an Individual

INTRODUCTION

Knowledge of normal range of size and volume of abdominal organs plays a vital role in clinical practices as various medical conditions affects the abdominal organs causing alteration in their dimensions.

AIM

The present retrospective study was done to establish the normal range of renal volume in study population and to see the correlation between renal volume and body weight of an individual.

MATERIALS AND METHODS

Computed tomographic evaluations of kidneys were performed on 140 kidneys of 70 individuals who had undergone abdominal CT scan for indications other than renal disease. We also excluded the patients diagnosed to have renal cysts, hydronephrosis or other renal diseases on CT examination. Renal length, width and depth were measured. Renal volume of both the kidneys was calculated by formula Kidney Volume (KV) =Л/6 x Renal length (L) x Renal width (W) x Renal depth (D). Various body parameters like age, weight, sex were also recorded in the data sheet.

RESULTS

Mean renal volume for the right kidney was 83.26±18.33 cm³ for females (33 females out of 70) and 103.92±23.27 cm³ for males (37 males out of 70). However, mean renal volume for the left kidney was 89.17±19.41 cm³ in females and 106±26.79 cm³ in males. Left renal volume was apparently more than right renal volume, though statistically insignificant. In males, mean kidney volume was found to be 104.96 cm³ whereas in females, it was found to be 86.21 cm³. Kidney volume was found to be significantly greater in males than females among study population (t=3.79, p=0.0001). Renal volume significantly correlated with age and body weight of an individual.

CONCLUSION

This study is a sincere attempt to establish a normograms of renal volume in study population. For the clinical assessment of renal pathologies, knowledge of renal volume is a vital parameter. In study group, most significant parameter associated with renal volume is body weight which can be used as an adjunct while evaluating renal pathological conditions. Of all the radiological imaging techniques, abdominal coronal computed tomography scan provides most accurate renal measurements.

Comparison between Two-sample Method with 99mTc-diethylenetriaminepentaacetic acid, Gates' Method and Estimated Glomerular Filtration Rate Values by Formula Based Methods in Healthy Kidney Donor Population

Purpose of the Study:

Glomerular filtration rate (GFR) is the most important parameter for the assessment of renal function. GFR by plasma sampling technique is considered accurate in the selection of donors for renal transplantation. Estimated GFR (eGFR) calculations using Gates’ method and Modification of Diet in Renal Disease (MDRD) and Cockcroft–Gault (CG) equations are simple methods but have not been validated in the Indian population. Hence, we aimed to assess the correlation between these three techniques.

Materials and Methods:

The plasma sampling technique was done using two samples at 60 and 180 min after injection of 1 mCi (37MBq) ^99mTc-diethylenetriaminepentaacetic acid (^99mTc-DTPA) in 66 healthy donors. Age, sex, height, weight, and plasma creatinine were recorded. Normalized GFR (nGFR) by two-sample method and eGFR (for Gates’, MDRD, and CG) values were calculated using formulae.

Results:

There were 14 male and 52 female donors. Mean age was 46.56 ± 12.88 years (24–69 years). Mean height was 153.74 ± 8.35 cm, whereas mean weight was 56.97 ± 11.88 kg. Mean nGFR value was 80.4 for two-sample method while mean eGFR value for Gates’, CG, and MDRD were 83.3, 89.36, and 97.47 ml/min/1.73 m² (eligibility value at our institution = 70), respectively. While the correlation between nGFR and eGFR CG and MDRD was weak moderate (correlation coefficient = 0.5), nGFR and eGFR Gates’ had a moderate correlation (0.686). Mean total bias for eGFR Gates’, CG, and MDRD were 2.87, 8.93, and 17.0, respectively. P₃₀ of eGFR Gates’, CG and MDRD were 60.6%, 57.6%, and 62.1%, respectively.

Conclusions:

Due to the large variability in eGFR Gates’, CG and MDRD, nGFR estimation using the plasma sampling technique with ^99mTc-DTPA appears necessary while screening healthy donors for renal transplantation.

Quantification of excretory renal function and urinary protein excretion by determination of body cell mass using bioimpedance analysis

BACKGROUND

Creatinine clearance (CrCl) based on 24 h urine collection is an established method to determine glomerular filtration rate (GFR). However, its measurement is cumbersome and the results are frequently inaccurate. The aim of this study was to develop an alternative method to predict CrCl and urinary protein excretion based on plasma creatinine and the quantification of muscle mass through bioimpedance analysis (BIA).

METHODS

In 91 individuals with normal and impaired renal function CrCl was measured from 24 h urine excretion and plasma creatinine concentration. A model to predict 24 h-creatininuria was developed from various measurements assessing muscle mass such as body cell mass (BCM) and fat free mass (FFM) obtained by BIA, skinfold caliper and other techniques (training group, N = 60). Multivariate regression analysis was performed to predict 24 h-creatininuria and to calculate CrCl. A validation group (N = 31) served to compare predicted and measured CrCl.

RESULTS

Overall (accuracy, bias, precision, correlation) the new BIA based prediction model performed substantially better compared with measured CrCl (P15 = 87 %, bias = 0, IQR of differences = 7.9 mL/min/1.73 m(2), R = 0.972) versus established estimation formulas such as the 4vMDRD (P15 =  6 %, bias = -8.3 mL/min/1.73 m(2), IQR = 13.7 mL/min/1.73 m(2), R = 0.935), CKD-EPI (P15 = 29 %, bias = -7.0 mL/min/1.73 m(2), IQR = 12.1 mL/min/1.73 m(2), R = 0.932, Cockcroft-Gault equations (P15 = 55 %, bias = -4.4 mL/min/1.73 m(2), IQR = 9.0 mL/min/1.73 m(2), R = 0.920). The superiority of the new method over established prediction formulas was most obvious in a subgroup of individuals with BMI > 30 kg/m(2) and in a subgroup with CrCl > 60 mL/min/1.73 m(2). Moreover, 24 h urinary protein excretion could be estimated accurately by normalization with 24 h-creatininuria derived from BIA based BCM.

CONCLUSION

Prediction of CrCl based on estimated urinary creatinine excretion determined from measurement of BCM by BIA technique is both accurate and convenient to quantify renal function in normal and diseased states. This new method may become particularly helpful for the evaluation of patients with borderline renal insufficiency and/or with abnormal body composition.

Comparison between Three Different Equations for the Estimation of Glomerular Filtration Rate in Omani Patients with Type 2 Diabetes Mellitus

OBJECTIVES

Estimated glomerular filtration rate (eGFR) is an important component of a patient's renal function profile. The Modification of Diet in Renal Disease (MDRD) equation and the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation are both commonly used. The aim of this study was to compare the performance of the original MDRD186, revised MDRD175 and CKD-EPI equations in calculating eGFR in type 2 diabetes mellitus (T2DM) patients in Oman.

METHODS

The study included 607 T2DM patients (275 males and 332 females, mean age ± standard deviation 56 ± 12 years) who visited primary health centres in Muscat, Oman, during 2011 and whose renal function was assessed based on serum creatinine measurements. The eGFR was calculated using the three equations and the patients were classified based on chronic kidney disease (CKD) stages according to the National Kidney Foundation Kidney Disease Outcomes Quality Initiative guidelines. A performance comparison was undertaken using the weighted kappa test.

RESULTS

The median eGFR (mL/min/1.73 m(2)) was 92.9 for MDRD186, 87.4 for MDRD175 and 93.7 for CKD-EPI. The prevalence of CKD stage 1 was 55.4%, 44.7% and 57% while for stages 2 and 3 it was 43.2%, 54% and 41.8%, based on MDRD186, MDRD175 and CKD-EPI, respectively. The agreement between MDRD186 and CKD-EPI (к 0.868) was stronger than MDRD186 and MDRD175 (к 0.753) and MDRD175 and CKD-EPI (к 0.730).

CONCLUSION

The performances of MDRD186 and CKD-EPI were comparable. Considering that CKD-EPI-based eGFR is known to be close to isotopically measured GFR, the use of MDRD186 rather than MDRD175 may be recommended.

Comparison of estimating equations for the prediction of glomerular filtration rate in kidney donors before and after kidney donation

The aim of this study is to investigate the usefulness of the GFR-estimating equations to predict renal function in kidney donors before and after transplantation. We compared the performance of 24-hour-urine–based creatinine clearance (24 hr urine-CrCl), the Cockcroft-Gault formula (eGFR_CG), the Modification of Diet in Renal Disease equation (eGFR_MDRD), and the Chronic Kidney Disease Epidemiology Collaboration equation (eGFR_CKD-EPI) with technetium-diethylenetriaminepentaacetic acid (^99mTc-DTPA) clearance (mGFR) in 207 potential kidney donors and 108 uninephric donors. Before donation, eGFR_CKD-EPI showed minimal bias and did not show a significant difference from mGFR (P = 0.65, respectively) while 24 hr urine-CrCl and eGFR_MDRD significantly underestimated mGFR (P<0.001 for each). Precision and accuracy was highest in eGFR_CKD-EPI and this better performance was more dominant when renal function is higher than 90 mL·min⁻¹·1.73 m⁻². After kidney donation, eGFR_MDRD was superior to other equations in precision and accuracy in contrast to before donation. Within individual analysis, eGFR_MDRD showed better performance at post-donation compared to pre-donation, but eGFR_CKD-EPI and eGFR_CG showed inferior performance at post-donation. In conclusion, eGFR_CKD-EPI showed better performance compared to other equations before donation. In a uninephric donor, however, eGFR_MDRD is more appropriate for the estimation of renal function than eGFR_CKD-EPI.

In-hospital major clinical outcomes in patients with chronic renal insufficiency presenting with acute coronary syndrome: data from a Registry of 8176 patients

OBJECTIVE

To assess the impact of chronic renal insufficiency (CRI) on in-hospital major adverse cardiac events across the acute coronary syndrome (ACS) spectrum.

PATIENTS AND METHODS

From January 29, 2007, through July 29, 2007, 6 adjacent Middle Eastern countries participated in the Gulf Registry of Acute Coronary Events, a prospective, observational registry of 8176 patients. Patients were categorized according to estimated glomerular filtration rate into 4 groups: normal (>or=90 mL/min), mild (60-89 mL/min), moderate (30-59 mL/min), and severe CRI (<30 mL/min). Patients' characteristics and in-hospital major adverse cardiac events in the 4 groups were analyzed.

RESULTS

Of 6518 consecutive patients with ACS, 2828 (43%) had mild CRI, 1304 (20%) had moderate CRI, and 345 (5%) had severe CRI. In CRI groups, patients were older and had a higher prevalence of hypertension, diabetes mellitus, and dyslipidemia. On admission, these patients had a higher resting heart rate and frequently had atypical and delayed presentations. Compared with the normal estimated glomerular filtration group, CRI groups were less likely to receive antiplatelet drugs, beta-blockers, angiotensin-converting enzyme inhibitors, and statins and were less likely to undergo coronary angiography. In-hospital heart failure, cardiogenic shock, and major bleeding episodes were significantly higher in all CRI groups. In multivariate analysis, mild, moderate, and severe CRI were associated with a higher adjusted odds ratio (OR) of death (mild: OR, 2.1; 95% confidence interval [CI], 1.2-3.7; moderate: OR, 6.7; 95% CI, 3.9-11.5; and severe: OR, 12.0; 95% CI, 6.6-21.7).

CONCLUSION

Across the ACS spectrum, patients with CRI had a worse risk profile, had more atypical and delayed presentations, and were less likely to receive evidence-based therapy. Chronic renal insufficiency of varying stages is an independent predictor of in-hospital morbidity and mortality.

Measurement of kidney volume with multi-detector computed tomography scanning in young Korean

PURPOSE

Kidney volume is regarded as the most precise indicator of kidney size. However, it is not widely used clinically, because its measurement is difficult due to the complex kidney shape. We attempted to evaluate the normal kidney volume in young Korean men by using multi-detector computed tomography (MDCT).

MATERIALS AND METHODS

We retrospectively reviewed MDCT data of young Korean men (113 patients). After data processing, we measured the volume and length of the kidneys. Body parameters (height, body weight, body-surface area, and total body water) and laboratory data were collected. Glomerular filtration rate (GFR) was calculated using Cockcroft-Gault (CG) equation.

RESULTS

The mean kidney volume was 205.29 +/- 36.81 cm(3); and mean kidney length was 10.80 +/- 0.69 cm. The former correlated significantly with height, body weight, body-surface area, and total body water (p < 0.05, correlation coefficient : gamma = 0.328, 0.649, 0.640, and 0.638, respectively). The latter also correlated significantly with all body indexes, however the correlation was weaker, except with height (p < 0.05, correlation coefficient : gamma = 0.457, 0.473, 0.505, and 0.503, respectively). Only kidney volume significantly predicted estimated GFR (adjusted R(2) = 0.431, F = 85.90 and p < 0.05).

CONCLUSION

The kidney volume measured with MDCT is correlated well with body parameters, and is useful to predict renal function.

Estimation and prediction of renal function in patients with renal tumor

PURPOSE

The goals of surgery for renal tumors include the preservation of renal function. When considering surgical options, it is important to accurately assess renal function and the risk of postoperative chronic kidney disease.

MATERIALS AND METHODS

An institutional database was used to identify 359 patients who underwent nephrectomy or partial nephrectomy. Creatinine clearance was estimated using 14 previously published models and compared with creatinine clearance measured using a 24-hour urine collection. Models were generated for predicting renal function following nephrectomy or partial nephrectomy. All models were validated with an external data set of 245 patients.

RESULTS

Models that accurately estimated creatinine clearance preoperatively and postoperatively were the Cockcroft-Gault model based on actual weight, and the Mawer, Björnsson, Hull and Martin models. In patients with an estimated creatinine clearance between 60 and 89 ml per minute preoperatively the risk of chronic kidney disease (creatinine clearance less than 60 ml per minute) after nephrectomy and partial nephrectomy was 58% and 15%, respectively (p <0.001). In patients undergoing nephrectomy age and weight were independent predictors of decreased creatinine clearance. A predictive model based on age and weight was highly accurate when applied to an external population (R = 0.757). A model for predicting renal function after partial nephrectomy based on age and tumor size was highly accurate in the external population (R = 0.848). A Web based tool was developed to estimate current and predict postoperative creatinine clearance (http://www.roswellpark.org/Patient_Care/Specialized_Services/Renal_Function_Estimator).

CONCLUSIONS

The Cockcroft-Gault model based on actual weight is 1 of 5 models that accurately estimates renal function in patients with a kidney tumor. Models were developed and externally validated to predict renal function following nephrectomy.