Bedside Estimation of the Glomerular Filtration Rate in Hospitalized Elderly Patients

Urinary tract infections in patients with renal insufficiency and dialysis - epidemiology, pathogenesis, clinical symptoms, diagnosis and treatment

Epidemiological studies show an increasing number of patients worldwide suffering from chronic kidney diseases (CKD), which are associated with a risk for progression to end-stage kidney disease (ESKD). CKD patients stage 2-5, patients with regular chronic dialysis treatment (hemo- or peritoneal dialysis), and patients suffering from kidney allograft dysfunction are at high risk to develop infections, e.g. urinary tract infections (UTI) and/or sepsis (urosepsis). These groups show metabolic disturbance, chronic inflammation, and impaired immunocompetence. Escherichia coli is still the most common pathogen in UTI. A wide variety of other pathogens may be involved in UTI. Urological interventions, catheterization, as well as repeated courses of antibiotics contribute to an increased challenge of antimicrobial resistance. The diagnosis of UTI in CKD is based on standard clinical and laboratory criteria. Pyuria (≥10 leucocytes/µl) is more often observed in patients with oligoanuria and low bacterial colony counts. The treatment strategies for this population are based on the same principles as in patients with normal renal function. However, drugs cleared by the kidney or by dialysis membranes need dose adjustment. Antimicrobials with potential systemic toxicity and nephrotoxicity should be administered with caution.

Prognostic value of estimated glomerular filtration rate in hospitalized elderly patients

A multicenter observational study, REPOSI (REgistro POliterapie Società Italiana di Medicina Interna), was conducted to assess the prognostic value of glomerular filtration rate (eGFR) on in-hospital mortality, hospital re-admission and death within 3 months, in a sample of elderly patients (n = 1,363) admitted to 66 internal medicine and geriatric wards. Based on eGFR, calculated by the new Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula, subjects at hospital admission were classified into three groups: group 1 with normal eGFR (≥60 ml/min/1.73 m(2), reference group), group 2 with moderately reduced eGFR (30-59 ml/min/1.73 m(2)) and group 3 with severely reduced eGFR (<30 ml/min/1.73 m(2)). Patients with the lowest eGFR (group 3) on admission were more likely to be older, to have a greater cognitive and functional impairment and a high rate of comorbidities. Multivariable logistic regression analysis showed that severely reduced eGFR at the time of admission was associated with in-hospital mortality (OR 3.00; 95% CI 1.20-7.39, p = 0.0230), but not with re-hospitalization (OR 0.97; 95% CI 0.54-1.76, p = 0.9156) or mortality at 3 months after discharge (OR 1.93; 95% CI 0.92-4.04, p = 0.1582). On the contrary, an increased risk (OR 2.60; 95% CI 1.13-5.98, p = 0.0813) to die within 3 months after discharge was associated with decreased eGFR measured at the time of discharge. Our study demonstrates that severely reduced eGFRs in elderly patients admitted to hospital are strong predictors of the risk of dying during hospitalization, and that this measurement at the time of discharge helps to predict early death after hospitalization.

[Clinical pharmacology and aging]

Clinicians must be aware that aging can lead to changes in the pharmacokinetics and pharmacodynamics of many drugs. Drug distribution may be modified with aging secondarily to the decrease of serum albumin and to modifications of body composition (increase in the proportion of fat mass and decrease of lean mass). Hepatic metabolism of several drugs is reduced with age, especially drugs which depend of hepatic blood flow or P450 cytochroms. The incidence of renal failure increase largely with age. Glomerular filtration rate should be systematically estimated in older patients and, when needed, the doses of those drugs having significant renal elimination should be adjusted. In older patients, changes in the response to drugs can also develop, concerning specially the central nervous system (increased sensibility to any neurological effect of drugs), the cardiovascular system and the renal management of water and electrolytes. In many cases, the pharmacological changes associated to age are mild and requires no dose adjustment. However, many drugs should be adapted depending on the individual situation of each patient, particularly his renal function and nutritional state. Finally, some drugs should be avoided in older patients because of a bad effectiveness/tolerance ratio compared to alternatives.

Variability of glomerular filtration rate estimation equations in elderly Chinese patients with chronic kidney disease

Background

Chronic kidney disease (CKD) is recognized worldwide as a public health problem, and its prevalence increases as the population ages. However, the applicability of formulas for estimating the glomerular filtration rate (GFR) based on serum creatinine (SC) levels in elderly Chinese patients with CKD is limited.

Materials and methods

Based on values obtained with the technetium-99m diethylenetriaminepentaacetic acid (^99mTc-DTPA) renal dynamic imaging method, 319 elderly Chinese patients with CKD were enrolled in this study. Serum creatinine was determined by the enzymatic method. The GFR was estimated using the Cockroft–Gault (CG) equation, the Modification of Diet in Renal Disease (MDRD) equations, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, the Jelliffe-1973 equation, and the Hull equation.

Results

The median of difference ranged from −0.3–4.3 mL/min/1.73 m². The interquartile range (IQR) of differences ranged from 13.9–17.6 mL/min/1.73 m². Accuracy with a deviation less than 15% ranged from 27.6%–32.9%. Accuracy with a deviation less than 30% ranged from 53.6%–57.7%. Accuracy with a deviation less than 50% ranged from 74.9%–81.5%. None of the equations had accuracy up to the 70% level with a deviation less than 30% from the standard glomerular filtration rate (sGFR). Bland–Altman analysis demonstrated that the mean difference ranged from −3.0–2.4 mL/min/1.73 m². However, the agreement limits of all the equations, except the CG equation, exceeded the prior acceptable tolerances defined as 60 mL/min/1.73 m². When the overall performance and accuracy were compared in different stages of CKD, GFR estimated using the CG equation showed promising results.

Conclusions

Our study indicated that none of these equations were suitable for estimating GFR in the elderly Chinese population investigated. At present, based on overall performance, as well as performance in different CKD stages, the CG equation may be the most accurate for estimating GFR in elderly Chinese patients with CKD.

Comparative evaluation of the Cockcroft-Gault Equation and the Modification of Diet in Renal Disease (MDRD) study equation for drug dosing: an opinion of the Nephrology Practice and Research Network of the American College of Clinical Pharmacy

Accurate assessment of kidney function is an important component of determining appropriate drug dosing regimens. Nearly all manufacturer-recommended dosage adjustments are based on creatinine clearance ranges derived from clinical pharmacokinetic studies performed during the drug development process. The Cockcroft-Gault (CG) equation provides an estimate of creatinine clearance and is the equation most commonly used to determine drug dosages in patients with impaired kidney function. The Modification of Diet in Renal Disease (MDRD) study equation has also been proposed for this purpose. Published studies report that drug dosages determined by the two equations do not agree in 10-40% of cases. However, interpretation and comparison of these studies are complicated by the variable creatinine methods used for calculating CG and MDRD estimates, the patient populations studied, and a lack of outcomes data demonstrating the clinical significance of dosing discrepancies. Moreover, the impact of reporting standardized serum creatinine values on the accuracy of the CG equation and corresponding drug dosing regimens have been questioned. Currently, no prospective pharmacokinetic studies have been conducted with use of the MDRD equation to generate dosing recommendations, and limited data are available to support its use in some patient populations representing demographic extremes. Collectively, these issues have resulted in considerable confusion among clinicians and have fueled a healthy debate on whether or not to use the MDRD equation to determine drug dosages. Each of these issues is reviewed, and a proposed algorithm for using creatinine-based kidney function assessments in drug dosing is provided. Knowledge of the advantages, limitations, and clinical role of each equation will facilitate their safe and effective use in drug dosing.

Comparison of different glomerular filtration methods in the elderly: which formula provides better estimates?

OBJECTIVES

Technetium-99m diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) is an ideal radioisotopic method having a high correlation with inulin clearance for the determination of glomerular filtration rate (GFR). Different formulas like creatinine clearance (CrCl) in 24 h urine samples, Cockroft-Gault formula (CGF), and modification of diet in renal disease (MDRD) are being used to come up with an estimate. In this study, we compared (99m)Tc-DTPA with the formulas mentioned above in an attempt to best identify the method that would yield the nearly ideal GFR estimates in the elderly.

MATERIALS AND METHODS

In 76 patients who were admitted to our clinic, we measured 24 h urine volume (V), urine creatinine (Ucr), and serum creatinine (Scr) levels together with CrCl, Scr, serum urea (Su), and albumin (Alb) levels. By using coefficients identified for age, gender, and race, we calculated modification of diet in renal disease 1 (MDRD1). Different from MDRD1, we calculated modification of diet in renal disease 2 (MDRD2) that does not include Su and Alb parameters and formulas like CGF that include Scr, age, gender, and weight parameters to come up with GFR levels. All patients underwent (99m)Tc-DTPA procedure.

RESULTS

The mean of the GFR values measured by (99m)Tc-DTPA was 54.3 ± 19.9. The means of GFR values calculated by CrCl, MDRD1, MDRD2, and CGF were 58.0 ± 30.5, 60.9 ± 22.1, 54.4 ± 20.1, and 57.9 ± 22.4, respectively. GFR as measured by (99m)Tc-DTPA showed statistically significant correlations with the results of other methods (p < 0.001 for all methods). The most significant correlation was with MDRD1.

CONCLUSION

MDRD1 can be used for next to ideal and accurate predictions of GFR in the elderly in the daily practice.

How do laboratory specialists advise clinicians concerning the use and interpretation of renal tests?

BACKGROUND

The aim of this study was to elucidate how laboratory specialists advise clinicians concerning renal parameters and to compare their advice with guideline recommendations.

METHODS

A questionnaire was distributed to laboratory specialists in Norway and The Netherlands together with two case histories from a primary health-care setting and one from a hospital setting, simulating questions from clinicians. The investigations that laboratory specialists suggested were compared to a test panel that was predefined based on clinical practice guideline recommendations (the 'recommended test panel'). The critical differences between two test results (creatinine, estimated glomerular filtration rate [eGFR] and albumin/creatinine ratio [ACR]) and the anticipated precision of the MDRD equation were evaluated.

RESULTS

Fifty-two of the 100 laboratory specialists responded, and most of these were regularly contacted by clinicians to discuss laboratory results. Less than 30% would suggest using the recommended test panel to evaluate renal function in the two primary-care patients. For creatinine and eGFR, median changes stated to signal improvement or deterioration in renal function (creatinine: -14% and +14%, respectively; eGFR: +18% and -13%, respectively) were similar to what could be calculated using information on analytical and within-subject variation from the literature. There were variable critical differences for the ACR results (median values of -50% for improvement and +67% for deterioration). Only 23% of the participants would recommend a gold standard clearance examination for a patient who was to undergo nephrotoxic chemotherapy.

CONCLUSION

Questions from GPs about renal parameters are answered differently by laboratory specialists, and adherences to guideline recommendations are low on some issues.

Stability of plasma creatinine concentrations in acute complex long-stay admissions to a general medical service

Assessment of glomerular filtration rate (GFR) is essential for calculating safe dosages of renally cleared drugs. Formulae for estimating reliable GFRs assume that plasma creatinine concentrations are stable. This study evaluates the variability of plasma creatinine (PCr) concentrations in patients admitted acutely to hospital. From 2,293 newly admitted patients, those in whom a subsequent clinically significant change (> 20%) in PCr had occurred were identified. Median age was 81.1 years. Median baseline PCr was 90 umol/l (eGFR 60 ml/min). In total, 46.3% of the patients had a PCr that varied > 20% from baseline three to seven days following admission. A 10-year increase in age increased the odds of a rise in PCr over the next week by 11.1% (odds ratio = 1.11, 95% confidence interval = 1.03, 1.20; p = 0.007). Overall, baseline creatinine was a poor predictor of subsequent variation in PCr. GFR formulae for calculating renally-cleared drug dosages should be used with caution in elderly patients admitted acutely to hospital.

Methods to evaluate renal function in elderly patients: a systematic literature review

CONTEXT

multiple studies of elderly patients show that the prevalence of chronic renal failure in people aged 65 years and older is dependent on the method used to calculate the glomerular filtration rate. We performed a systematic literature search with research question: What is the best method that could be applicable in clinical practice for evaluating renal function in the elderly? Studies using inulin, Cr-51-EDTA, Tc-DTPA or iohexol assays as the gold standard were included.

METHODS

we searched the PubMed and EMBASE databases. Articles found were screened first by title and abstract and then by five criteria. Retained articles were scored using an adapted version of QUADAS.

RESULTS

twelve articles had an identified population or subpopulation aged 65 years and older. The studies were heterogeneous with regard to the population investigated and the statistical procedures used to compare the methods and equations with the gold standard. The Cockcroft-Gault (CG) and MDRD equations and the serum cystatin C concentration produced the highest correlations with the gold standard.

CONCLUSIONS

no accurate method to evaluate renal function in the elderly was found. Serum cystatin C concentration and the CG and MDRD formula might be valuable parameters, although there is insufficient evidence.

Acute medical management of the non-ST-segment elevation acute coronary syndromes (NSTE-ACS) in older patients

Older patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS) represent many clinical challenges. For example diagnosis can be difficult, and comorbidities are common. Furthermore, NSTE-ACS is particularly common in older patients (>60% of acute myocardial infarctions occurring in patients aged 65 years or older) and the mortality associated with NSTE-ACS is particularly high. Despite these many concerns, evidence from clinical trials based on this group of patients is limited. Future prospective clinical trials should therefore more accurately reflect the NSTE-ACS patient population by including more elderly patients and including efficacy endpoints that are relevant for these patients. Furthermore, the lack of clear clinical evidence in this population means that the current treatment guidelines do not fully address the needs of elderly patients. Several recent clinical trials have highlighted some of the main considerations we should make when treating elderly patients with NSTE-ACS. Different therapy options in the pharmacological management of NSTE-ACS in this age group are also discussed.

Evaluation of the Modification of Diet in Renal Disease equation (eGFR) against simultaneous, dual-marker multi-sample measurements of glomerular filtration rate

BACKGROUND

Estimation of glomerular filtration rate (GFR) using plasma creatinine remains controversial, especially when GFR approaches normal values. The aim was to re-examine estimated GFR (eGFR) using dual-reference GFR measurements.

METHODS

eGFR (simplified modified Modification of Diet in Renal Disease equation) was compared with GFR measured with iohexol for predicting GFR measured with (51)Cr-ethylenediaminetetraacetic acid (EDTA). Dual six-sample GFR (20-240 min postinjection) was measured in 60 patients and 20 normal volunteers with (51)Cr-EDTA (GFR(EDTA)) and iohexol (GFR(iohexol)) injected into separate arms and sampled contralaterally. This was repeated in the normal volunteers under fasting conditions (twice in nine). Percentage bias, imprecision (SD of bias) and disagreement (sign-less difference) between eGFR and GFR(EDTA) were compared with those between GFR(iohexol) and GFR(EDTA).

RESULTS

Changes between fasting and postprandial eGFR correlated significantly with corresponding changes in GFR(iohexol) and GFR(EDTA). eGFR predicted GFR(EDTA) less precisely (SD 19.9%) than GFR(iohexol) (10.5%; P < 0.01). Although eGFR showed a poorer correlation with GFR(EDTA) when GFR(EDTA) > 80 mL/min/1.73 m(2) compared with <80 mL/min/1.73 m(2), there was no significant difference with respect to imprecision or disagreement of >20 or 30%. However, eGFR was closer than GFR(iohexol) to GFR(EDTA) in a higher fraction of studies when GFR(EDTA) > 80 mL/min/1.73 m(2) (28/60) than when it was <80 mL/min/1.73 m(2) (9/37; P < 0.05).

CONCLUSION

eGFR is inferior to GFR(iohexol) for predicting GFR(EDTA). The disagreement between GFR(iohexol) and GFR(EDTA) illustrates the extent to which uncertainty in GFR(EDTA) contributes to the performance of eGFR. eGFR performs no better at lower, compared with higher levels of GFR.

Evaluating influencing factors in estimation of renal function by extending the Bland-Altman approach

Method comparison is frequently requested when newly developed methods are evaluated. In medical sciences in particular, numerous articles are published every year concerning new methods for improving diagnostics. Among several statistical approaches used to provide essential test characteristics, the Bland-Altman method is well established, but actually provides no evaluation of possible factors influencing test quality. We propose an analysis of residuals obtained from the Bland-Altman data alleviating the determination of possible factors influencing accuracy and precision compared with different methods and give a short tutorial on application of Bland-Altman analysis. We illustrate this extension of the classical Bland-Altman method with an actual clinical example: estimation of renal function applying the common formula of Cockcroft and Gault. The influence of diabetes, gender and age on accuracy and precision of this estimation is analysed and inulin clearance is used as the gold standard. The subsequent analysis of residuals allows detection of the variables significantly influencing accuracy and precision. In the given example, diabetes and age, but not gender, are revealed as significant factors in glomerular filtration rate estimation when applying the Cockcroft formula.

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 ((SO)GFR), 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 (SO)GFR 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. (SO)GFR 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. (SO)GFR measured with Cr-51-EDTA is superior to eGFR.

Serum blood urea nitrogen and long-term mortality in acute ST-elevation myocardial infarction

INTRODUCTION

Renal dysfunction is associated with increased mortality in acute coronary syndromes and other cardiovascular diseases. The prognostic value of kidney dysfunction has been investigated using creatinine-based measures of renal function. Few data are available on the prognostic significance of blood urea nitrogen (BUN), a sensitive marker of hemodynamic alterations and renal perfusion.

METHODS

The relationship between estimated glomerular filtration rate (eGFR), BUN on admission and changes in BUN during hospital course and long-term mortality was evaluated in 1507 patients with acute ST-elevation myocardial infarction (STEMI).

RESULTS

During a median follow-up of 27 months (range, 12 to 44 months), 281 patients (18.6%) died. In multivariable Cox regression models, elevated BUN (>or=25 mg/dL) at admission was an independent predictor of mortality after adjustments for clinical variables and eGFR (adjusted hazard ratio [HR] 1.7; 95% confidence interval [CI] 1.2-2.3, P=0.0015). Similar results were obtained for elevated BUN/creatinine ratio (>or=25) at admission (adjusted HR 2.0; 95% CI 1.4-2.8; P<0.0001). An increase in BUN 50% above admission value occurred in 260 of patients (17.3%) during hospital course, and was associated with increased risk of mortality after adjustments of clinical variables, eGFR and BUN on admission (HR, 1.7 95% CI 1.3-2.2; P<0.0001).

DISCUSSION

Elevated BUN and BUN/creatinine ratio on admission are independent predictors of long-term mortality in patients with STEMI. An increase in BUN level during hospital course portends adverse outcome independent of eGFR and BUN on admission.

Prävention unerwünschter Arzneimittelwirkungen bei älteren Patienten

Adverse drug reactions are among the most common adverse events and a significant cause of preventable morbidity and mortality. As multimorbidity and polypharmacy are frequent in this population, the elderly are at special risk for adverse drug events, although the calendar age has not been proved as independent risk factor in this context. In particular falls and delirium are clinically significant and typical adverse drug events in the elderly. In this review mechanisms and factors which determine adverse drug re actions are described, and possible strategies for an effective prevention are given. This covers pharmacokinetic, pharmacogenetic and pharmacodynamic aspects as well as factors influencing individual adherence to drug therapy. A significant portion of adverse drug reaction may be prevented by a thorough indication and prudent monitoring of pharmacotherapy. Also adherence to pharmacotherapy may be improved by tailored and individual means referring to the patient's needs and expectancies. In the elderly functional limitations such as reduced cognitive abilities, reduced visual acuity and impaired dexterity determine an ineffective pharmacotherapy and medication errors. Hereby these functional limitations are significant predictors of adverse drug events in the context of self-management of pharmacotherapy. Testing of functional abilities as provided in the geriatric assessment is helpful to identify these factors. Among altered pharmacokinetic factors in the elderly, reduced renal function is most important to avoid overdosage. Although a precise measurement of renal function is not possible in a bed-side manner, an estimation of actual renal function utilizing estimation-formulas should always take place.

Kidney function estimating equations: where do we stand?

PURPOSE OF REVIEW

Estimation of the glomerular filtration rate (GFR) is central to the diagnosis, evaluation and management of chronic kidney disease. This review summarizes recent data on the performance of equations using serum creatinine to estimate the GFR, particularly the Modification of Diet in Renal Disease (MDRD) Study equation.

RECENT FINDINGS

During 2005 GFR estimation has received substantial attention with a focus on comparing the MDRD Study equation with the Cockcroft-Gault equation. Several large studies (n>500) have appeared. Most studies discuss creatinine calibration but few were able to standardize measurements. Studies that did calibrate the creatinine had improved performance. Overall, the MDRD Study equation performed well in populations with a low range of GFR and often outperformed the Cockcroft-Gault equation. Both equations have lower precision in high GFR populations, and the MDRD equation under-estimated the GFR in a number of studies. Efforts are underway to develop improved prediction equations by pooling data across many study populations.

SUMMARY

Equations for estimating the GFR from serum creatinine are useful for systematic staging of chronic kidney disease. The MDRD Study equation and systematic creatinine assay calibration improve the level of precision and accuracy in many settings. GFR estimates are less useful in the normal range of GFR, however, and are sensitive to the population under study.