An easy to calculate equation to estimate GFR based on inulin clearance

Donor Evaluation of Living Kidney Transplantation in the Aging Society

BACKGROUND

Because of the lack of organ donation, living kidney transplantation (LKT) is increasing worldwide. Recently, the number of elderly donors has been increasing, and the patients with end-stage kidney diseases are older than those in the previous decades. Due to the advanced ages, their glomerular filtration rates (GFR) decrease, and the comorbidities such as hypertension, diabetic condition, and obesity are common. The clinicians now have to give their unwilling consent to the LKT from the donors with expanded criteria.

SUMMARY

For the secure selection of donors, proper GFR measuring is essential. Although directly measured GFR (mGFR) was recommended in the guidelines, estimated GFR (eGFR) is used at the initial evaluation of donor renal function clinically. Many equations calculating eGFR have been published so far. In the selection of eGFR equations, the smaller difference between mGFR and eGFR and the closer relationship to the prevalence rates of comorbidities are requisite points. Therefore, we compared the specificity of the various eGFR equations. The eGFR calculated from the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation showed approximate reliability with minimal difference between mGFR and eGFR and the closer relationships to the prevalence rates of comorbidities.

KEY MESSAGE

The CKD-EPI-eGFR presented optimal performance in the donor renal function evaluation. Therefore, eGFR from the CKD-EPI equation is highly recommended in evaluating renal function in LKT donors.

Pharmacokinetic and pharmacodynamic considerations of antimicrobial drug therapy in cancer patients with kidney dysfunction

Patients with cancer have a high inherent risk of infectious complications. In addition, the incidence of acute and chronic kidney dysfunction rises in this population. Anti-infective drugs often require dosing modifications based on an estimate of kidney function, usually the glomerular filtration rate (GFR). However, there is still no preferential GFR formula to be used, and in acute kidney injury there is always a considerable time delay between true kidney function and estimated GFR. In most cases, the anti-infective therapy should start with an immediate and high loading dose. Pharmacokinetic as well as pharmacodynamic principles must be applied for further dose adjustment. Anti-infective drugs with time-dependent action should be given with the target of high trough concentrations (e.g., beta lactam antibiotics, penems, vancomycin, antiviral drugs). Anti-infective drugs with concentration-dependent action should be given with the target of high peak concentrations (e.g., aminoglycosides, daptomycin, colistin, quinolones). Our group created a pharmacokinetic database, called NEPharm, hat serves as a reference to obtain reliable dosing regimens of anti-infective drugs in kidney dysfunction as well as renal replacement therapy. To avoid the risk of either too low or too infrequent peak concentrations, we prefer the eliminated fraction rule for dose adjustment calculations.

The proxy of renal function that most accurately predicts short- and long-term outcome after acute coronary syndrome

AIMS

The aim of this study is to determine the most accurate renal function formula that predicts short- and long-term mortality in a wide spectrum of acute coronary syndrome (ACS) patients.

METHODS AND RESULTS

We analyzed 8,726 consecutive patients (46.3% ST-elevation myocardial infarction [STEMI] and 53.7% non-ST-elevation ACS [NSTE-ACS]) enrolled in the ACS survey in Israel. Renal function, assessed using 5 formulas as proxies of creatinine clearance or estimated glomerular filtration rate (Cockcroft-Gault, modification of diet in renal disease [MDRD], Chronic Kidney Disease Epidemiology Collaboration, Mayo quadratic, and inulin clearance based), varied in applying the different formulas. For both STEMI and NSTE-ACS patients, the Mayo formula yielded the highest mean value (88.9 ± 27.7 and 81.4 ± 29.2 mL/min per 1.73 m(2), respectively) and Chronic Kidney Disease Epidemiology Collaboration the lowest (73.0 ± 23.1 and 67.0 ± 24.1 mL/min per 1.73 m(2), respectively). Using multivariate analysis, worse renal function was independently associated with increased mortality risk by 30% to 40% for each decrement of 10 U of creatinine clearance or estimated glomerular filtration rate in STEMI patients and by 25% to 30% for NSTE-ACS patients, using all 5 formulas. The only formula that more accurately predicted 1-year mortality than the MDRD formula was the Mayo quadratic formula with a 1-year net reclassification index of 0.26 and 0.14 for STEMI and NSTE-ACS patients, respectively, after multivariable adjustment.

CONCLUSION

Worse renal function was an independent predictor for short- and long-term mortality using all 5 formulas in a broad spectrum of ACS patients, but only the Mayo quadratic formula had better accuracy in predicting mortality relative to the MDRD, suggesting that it may be the preferred prognosticator among ACS patients.

Assessment and modeling of routinely used biochemical laboratory data of healthy individuals and end-stage renal failure (ESRF) patients by three different chemometric methods

BACKGROUND

In recent years, the use of biochemical markers has received increasing attention for purposes of risk assessment and clinical management in renal failure patients. Chemometric methods are often used in medical studies and there are already indications for their specific role as a tool of the medical statistics.

METHODS

Three chemometric methods, discriminant analysis (DA), binary logistic regression analysis (BLRA), and cluster analysis (CA), were used for assessment and modeling of routinely used biochemical laboratory data of 18 parameters that were determined from 185 healthy individuals (HIs) and 173 end-stage renal failure (ESRF) patients.

RESULTS

The above-mentioned chemometric methods were performed using the data set of 14 parameters since the rest 4 parameters did not present significant difference between healthy and patients. DA created a model using only ALB (Albumin), K (Potassium), TG (Triglyceride), and ALP (Alkaline phosphatase); BLRA model also used the above four parameters; CA classified all the cases into two clusters using the same four parameters and one more parameter, AST (aspartate aminotransferase).

CONCLUSIONS

This study provides models for assessment and modeling of routinely used biochemical laboratory data, finding groups of similarity among clinical tests usually determined on HIs and ESRF patients, contributing in data mining and reducing costs.

The old and new methods of assessing kidney function

Chronic kidney disease is a worldwide problem. Accurate assessment of kidney function is important for defining stages of kidney disease and assisting with drug dosing. Glomerular filtration rate (GFR) is a good index of the health of the kidney. Although measured GFR using an exogenous substance is the most accurate, it is difficult to obtain due to cost and resources. Equations calculating creatinine clearance and estimated GFR as a measure of kidney function have been developed using serum creatinine as a marker of kidney function. The Cockcroft-Gault, Modification of Diet in Renal Disease, and Chronic Kidney Disease Epidemiology Collaboration equations have been shown to have statistically significant differences in estimating GFR in various populations. Drug-dosing adjustments based on the various equations may differ. However, without clinical outcome data, it is yet to be determined whether these differences are clinically significant.

Higher body mass index is associated with higher fractional creatinine excretion in healthy subjects

BACKGROUND

Accurate glomerular filtration rate (GFR) measurement in normal to high range is important for epidemiological studies and workup for kidney donation. Creatinine-based equations perform poorly in this GFR range. Creatinine clearance (CrCl) provides a substitute, provided urine is collected accurately and tubular creatinine handling can be accounted for. The latter is poorly characterized in the normal GFR range.

METHODS

Therefore, we studied performance of CrCl, fractional creatinine excretion (FE(creat)) and its determinants in 226 potential kidney donors (47% males, mean 53 ± 10 years). GFR was assessed as (125)I-iothalamate clearance, simultaneously with 2-h CrCl and 24-h CrCl.

RESULTS

Mean GFR was 101 ± 18, 2-h CrCl 110 ± 20 and 24-h CrCl 106 ± 29 mL/min/1.73 m(2). Mean bias of 24 h CrCl was 7.4 [inter-quartile range -6.7 to 20.0] mL/min/1.73 m(2), precision (R(2)) 0.39 and 30% accuracy 82%. Mean FE(creat) was 110 ± 11%. FE(creat) correlated with body mass index (BMI) (r = 0.34, P < 0.001). Consequently, bias of 24-h CrCl increased from 2.7 (inter-quartile range -6.5 to 16.7) to 8.6 (inter-quartile range -5.8 to 20.5) and 12.6 (inter-quartile range 7.0 to 25.4) mL/min in subjects with BMI <25, 25-30 and >30 kg/m(2), respectively (P < 0.05). On multivariate analysis, BMI and gender were predictors of FE(creat).

CONCLUSIONS

CrCl systematically overestimates GFR in healthy subjects. The overestimation significantly correlates with BMI, with higher FE(creat) in subjects with higher BMI. The impact of BMI on tubular creatinine secretion can be accounted for, when using CrCl for GFR assessment in the normal to high range, by the following formula: GFR = 24-h CrCl - (22.75 + 0.76 × BMI - 0.29 × mean arterial pressure (-6.11 if female).