The reliability of different formulae to predict creatinine clearance

How to estimate glomerular filtration rate in sub-Saharan Africa: design and methods of the African Research into Kidney Diseases (ARK) study

BACKGROUND

Chronic kidney disease (CKD) is a substantial cause of morbidity and mortality worldwide with disproportionate effects in sub-Saharan Africa (SSA). The optimal methods to estimate glomerular filtration rate (GFR) and therefore to determine the presence of CKD in SSA are uncertain. We plan to measure iohexol excretion to accurately determine GFR in Malawi, South Africa and Uganda. We will then assess the performance of existing equations to estimate GFR and determine whether a modified equation can better improve estimation of GFR in sub-Saharan Africa.

METHODS

The African Research on Kidney Disease (ARK) study is a three-country study embedded within existing cohorts. We seek to enrol 3000 adults > 18 years based on baseline serum creatinine. Study procedures include questionnaires on socio-demographics and established risk factors for kidney disease along with anthropometry, body composition, blood pressure, blood chemistry and urine microscopy and albuminuria. We will measure GFR (mGFR) by plasma clearance of iohexol at 120, 180 and 240 min. We will compare eGFR determined by established equations with mGFR using Bland-Altman plots. We will use regression methods to estimate GFR and compare the newly derived model with existing equations.

DISCUSSION

Through the ARK study, we aim to establish the optimal approach to estimate GFR in SSA. The study has the advantage of drawing participants from three countries, which will increase the applicability of the findings across the region. It is also embedded within established cohorts that have longitudinal information and serial measures that can be used to characterize kidney disease over a period of time. This will help to overcome the limitations of previous research, including small numbers, selected population sub-groups, and lack of data on proteinuria. The ARK collaboration provides an opportunity for close working partnerships across different centres, using standardized protocols and measurements, and shared bio-repositories. We plan to build on the collaboration for this study for future work on kidney disease in sub-Saharan Africa, and welcome additional partners from across the continent.

[Acute renal failure in the elderly]

Acute renal failure in elderly patients is common and likely to become more so as life expectancy in France continues to grow. The chances of acute renal failure occurring in the elderly are increased by changes in renal function and the effects of various chronic diseases such as diabetes, hypertension and obstructive urological disorders, all of which increase in incidence with age. The elderly may develop all types of the disease but are most prone to drug-related acute renal failure. The diagnostic and therapeutic strategies adopted are the same as those for adult patients but should take into account the potential risks and benefits in this specific age group. However, age should no longer be considered as the sole determining factor in diagnostic and therapeutic decisions. The elderly are among those who benefit most from preventive measures against acute renal failure.

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).

Relationship between renal function and functional decline: role of the estimating equation

BACKGROUND

Several formulas are available to estimate glomerular filtration rate (GFR) at the bedside. A decrease in GFR has been associated with poorer performance. We hypothesized that it is related to worsening disability as well. The aim of this study was to evaluate whether the Modification of Diet in Renal Disease formulas can predict worsening disability better than the classic Cockcroft-Gault formula or the measured creatinine clearance.

METHODS

We studied 666 participants in the InCHIANTI study with 6 years of follow-up data. We evaluated whether directly measured creatinine clearance and GFR estimated using the Modification of Diet in Renal Disease and Cockcroft-Gault formulas predict new disability defined as the loss of ≥ 1 ADL over the 6-year follow-up.

RESULTS

The mean age was 73.1 years (SD: 6.1), 57.7% were women. Fewer than 5% of participants were disabled at baseline. Eighty-one (12.2%) participants experienced a decline in activities of daily life score at follow-up. Declining GFR was associated with increasing risk of worsening disability (Mantel-Haenszel P < .001), with an increased steepness in the curve at GFR below 60 mL/min. The relative risks for worsening disability in people with GFR less than 60 mL/min/m were 3.19 (95% CI: 2.12-4.79) and 4.40 (95% CI: 2.80-6.94) using the Modification of Diet in Renal Disease and the Cockcroft-Gault equations, respectively. The corresponding figures obtained with measured creatinine clearance was 3.95 (95% CI: 2.60-6.01). After adjustment for potential confounders, however, these estimates were substantially reduced.

CONCLUSION

Estimation of renal function with the Cockcroft-Gault or Modification of Diet in Renal Disease formulas can help to identify elderly at risk of worsening disability. The mechanism by which reduced kidney function predicts disability should be further investigated.

High extracellular levels of cefpirome in unaffected and infected lung tissue of patients

OBJECTIVES

the objective of the present investigation was to measure the extracellular concentrations of cefpirome in unaffected and infected lung tissue of septic patients.

METHODS

a single intravenous dose of 30 mg/kg total body weight of cefpirome was administered to eight patients every 12 h prior to insertion of microdialysis probes into lung tissue.

RESULTS

the median (minimum, maximum) peak concentration (C(max)), time to C(max) (T(max)), area under the concentration-time curve from 0 to 4 h (AUC(0-4)) and AUC(0-∞) of unbound cefpirome for unaffected lung were 48 (32, 107) mg/L, 0.83 (0.17, 3.17) h, 117 (60, 177) mg · h/L and 182 (80, 382) mg · h/L, respectively. The corresponding values for infected lung tissue were 45 (6, 122) mg/L, 1.17 (0.83, 2.83) h, 92 (17, 253) mg · h/L and 206 (49, 379) mg · h/L, respectively. The median apparent terminal elimination half-lives (t(½z)) of cefpirome were 2.61, 3.05 and 3.39 h for plasma, unaffected lung and infected lung, respectively. The median ratios of the AUC(0)(-∞) for lung to the AUC(0)(-∞) for plasma were 0.63 (0.19, 1.55) and 0.46 (0.32, 0.98) for unaffected and infected lung, respectively.

CONCLUSIONS

we provide strong evidence that cefpirome penetrates effectively into the extracellular space fluid of lung tissue. Under steady-state conditions, the median concentrations of cefpirome in plasma, unaffected lung and infected lung exceeded the MICs of the majority of relevant bacteria over the entire dosing interval of up to 12 h after intravenous administration of a dose of 30 mg/kg total body weight.

Renal disease in systemic sclerosis with normal serum creatinine

Prognosis of systemic sclerosis largely depends on involvement of internal organs. The aim was to evaluate renal impairment in patients with systemic sclerosis by measuring the Glomerular filteration rate (GFR) and then calculating the GFR using the Cockgroft and Gault formula and the Modification of Diet in Renal Disease Equation (MDRD) formula. Thirty one scleroderma patients were recruited from the Rheumatology and Rehabilitation Department, Cairo University Hospitals, mean age 43.25 +/- 11.28 years, 31 healthy controls were included. Disease severity was done using Medsger score. GFR was measured using classical Gates method TC99mDTPA. The modified Cockcroft and Gault formula and equation 7 from the MDRD were used for calculation of GFR. All patients had within normal serum creatinine levels. A normal GFR (>89ml/min) was found in 45.1%. Gates method showed reduced GFR was reported in 54.9%. Stage II chronic kidney disease (60-89 ml/min) found 32.3%, and stage III (30-59 ml/min) in 22.6%. The formulae used showed reduction of GFR in 35.29% of those affected by the Cockcroft-Gault and in 41.17% of those affected using the MDRD. No correlation to patients' age, disease duration, or severity. A positive correlation was also reported between the presence of renal involvement and pulmonary vascular involvement p = 0.04. Gates method showed reduction of the GFR in 54.9% of the systemic sclerosis patients. The formulae used were not as precise as the measured GFR in diagnosing all cases with subclinical renal involvement. Patients with systemic sclerosis should be screened for renal involvement irrespective of disease severity or duration.

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.

Clinical Use and Pathogenetic Basis of Laboratory Tests for the Evaluation of Primary Arterial Hypertension

This review focuses on the laboratory biochemical tests that are useful in the diagnostic approach to the hypertensive patient. A "minimal" diagnostic laboratory work-up, including a small number of tests that are simple and relatively inexpensive, is first described. Because these tests provide basic information on the presence of major cardiovascular (CV) risk factors and target organ damage, and might give some clues to the presence of a secondary form of hypertension (HT), they should be performed on all patients presenting with HT. Other tests that are aimed at assessing the overall CV risk, a major determinant of prognosis that dictates the therapeutic strategy in the individual HT patient, are then discussed. They allow identification of major CV risk factors and associated clinical conditions which, if present, lead to a substantial change of therapeutic strategy. The role of C-reactive protein as a marker of atherosclerosis and its predictive value for CV events are also discussed. Finally, a section is devoted to tests that are currently confined to research purposes, such as markers of endothelial function including endothelin-1, homocysteine and genetic analysis.

Prevalence of estimated GFR reporting among US clinical laboratories

BACKGROUND

Routine laboratory reporting of estimated glomerular filtration rate (eGFR) may help clinicians detect kidney disease. The current national prevalence of eGFR reporting in clinical laboratories is unknown; thus, the extent of the situation of laboratories not routinely reporting eGFR with serum creatinine results is not quantified.

DESIGN

Observational analysis.

SETTING

National Kidney Disease Education Program survey of clinical laboratories conducted in 2006 to 2007 by mail, web, and telephone follow-up.

PARTICIPANTS

A national random sample, 6,350 clinical laboratories, drawn from the Federal Clinical Laboratory Improvement Amendments database and stratified by 6 major laboratory types/groupings.

PREDICTORS

Laboratory reports serum creatinine results.

OUTCOMES

Reporting eGFR values with serum creatinine results.

MEASUREMENTS

Percentage of laboratories reporting eGFR along with reporting serum creatinine values, reporting protocol, eGFR formula used, and style of reporting cutoff values.

RESULTS

Of laboratories reporting serum creatinine values, 38.4% report eGFR (physician offices, 25.8%; hospitals, 43.6%; independents, 38.9%; community clinics, 47.2%; health fair/insurance/public health, 45.5%; and others, 43.2%). Physician office laboratories have a reporting prevalence lower than other laboratory types (P < 0.001). Of laboratories reporting eGFR, 66.7% do so routinely with all adult serum creatinine determinations; 71.6% use the 4-variable Modification of Diet in Renal Disease Study equation; and 45.3% use the ">60 mL/min/1.73 m(2)" reporting convention. Independent laboratories are least likely to routinely report eGFR (50.6%; P < 0.05) and most likely to report only when specifically requested (45.4%; P < 0.05). High-volume laboratories across all strata are more likely to report eGFR (P < 0.001).

LIMITATIONS

Self-reporting by laboratories, federal database did not have names of laboratory directors/managers (intended respondents), assumed accuracy of federal database for sample purposes.

CONCLUSIONS

Routine eGFR reporting with serum creatinine values is not yet universal, and laboratories vary in their reporting practices.

Cardiovascular and renal outcome in subjects with K/DOQI stage 1-3 chronic kidney disease: the importance of urinary albumin excretion

BACKGROUND

The Kidney Disease Outcomes Quality Initiative guidelines aim to define chronic kidney disease (CKD) and classify its stages. Stage 3 CKD generally receives more attention than stage 1 or 2, because the more impaired glomerular filtration rate (GFR) in stage 3 suggests a higher cardiovascular and renal risk. In this study we evaluated cardiovascular and renal outcome in subjects with stage 1 and 2 CKD. For comparison, we also studied these outcomes in stage 3 CKD.

METHODS

We used data of 8495 subjects of the PREVEND study, a prospective community-based cohort study, with data on urinary albumin excretion (UAE) and serum creatinine available. As measure of cardiovascular outcome, combined cardiovascular morbidity and mortality was used. As renal outcome, mean annual change of estimated GFR (eGFR) was used.

RESULTS

6905 subjects had no CKD; 243, 856 and 491 subjects had stage 1, 2 and 3 CKD, respectively. During a median follow-up of 7.5 years 565 cardiovascular events occurred. Incidence rates of cardiovascular events were higher (P < 0.001 for all groups) in subjects with stage 1-3 CKD (17.2, 22.2 and 20.9 events/1000 person-years, respectively) than in subjects without CKD (7.0 events/1000 person-years). Using subjects without CKD as reference, age- and sex-adjusted hazard ratios [HR (95% CI)] were 2.2 (1.5-3.3), 1.6 (1.3-2.0) and 1.3 (1.0-1.7), respectively. Compared to subjects without CKD but similar baseline eGFR, subjects with stage 1 or 2 CKD showed a larger decline in eGFR (-1.1 versus -1.5 and -0.2 versus -0.6 ml/min/1.73 m(2)/year, respectively, both P < 0.01). When subjects with stage 3 CKD were stratified according to the absence or presence of a UAE >30 mg/24 h, age- and sex-adjusted HRs for CVD were 1.0 (0.7-1.4) and 1.6 (1.1-2.3) and the change in eGFR was 0.2 versus -0.3 ml/min/1.73 m(2)/year, respectively.

CONCLUSION

Subjects with stage 1 or 2 CKD have an increased risk for adverse cardiovascular and renal outcome and should receive equal attention as subjects with stage 3 CKD. Subdividing stage 3 CKD according to the presence or absence of a UAE >30 mg/24 h improves risk stratification within this stage.

Prevalence of chronic kidney disease in population-based studies: systematic review

BACKGROUND

Chronic kidney disease (CKD) is becoming a major public health problem worldwide. This article reviews the published evidence of prevalence of CKD in population-based study samples that used the standardized definition from the Kidney Disease Outcomes Quality Initiative of the National Kidney Foundation (K/DOQI) practice guideline, and particularly focus on performance of serum-creatinine based equations for GFR estimation. We provide a summary of available data about the burden of CKD in various populations.

METHODS

We performed a systematic review of available published data in MEDLINE. A combination of various keywords relevant to CKD was used in this research. Related data of included studies were extracted in a systematic way.

RESULTS

A total of 26 studies were included in this review. The studies were conducted in different populations, and the number of study participants ranged from 237 to 65181. The median prevalence of CKD was 7.2% in persons aged 30 years or older. In persons aged 64 years or older prevalence of CKD varied from 23.4% to 35.8%. Importantly, the prevalence of CKD strongly depended on which estimating equations were used. The Modification of Diet in Renal Disease Study (MDRD) equation was likely to be preferred in recent epidemiological studies compared to the adjusted Cockcroft-Gault (CG) equation.

CONCLUSION

Worldwide, CKD is becoming a common disease in the general population. Accurately detecting CKD in special groups remains inadequate, particularly among elderly persons, females or other ethnic groups such as Asians.

Trueness verification of actual creatinine assays in the European market demonstrates a disappointing variability that needs substantial improvement. An international study in the framework of the EC4 creatinine standardization working group

: The European In Vitro Diagnostics (IVD) directive requires traceability to reference methods and materials of analytes. It is a task of the profession to verify the trueness of results and IVD compatibility.

: The results of a trueness verification study by the European Communities Confederation of Clinical Chemistry (EC4) working group on creatinine standardization are described, in which 189 European laboratories analyzed serum creatinine in a commutable serum-based material, using analytical systems from seven companies. Values were targeted using isotope dilution gas chromatography/mass spectrometry. Results were tested on their compliance to a set of three criteria: trueness, i.e., no significant bias relative to the target value, between-laboratory variation and within-laboratory variation relative to the maximum allowable error.

: For the lower and intermediate level, values differed significantly from the target value in the Jaffe and the dry chemistry methods. At the high level, dry chemistry yielded higher results. Between-laboratory coefficients of variation ranged from 4.37% to 8.74%. Total error budget was mainly consumed by the bias. Non-compensated Jaffe methods largely exceeded the total error budget. Best results were obtained for the enzymatic method. The dry chemistry method consumed a large part of its error budget due to calibration bias.

: Despite the European IVD directive and the growing needs for creatinine standardization, an unacceptable inter-laboratory variation was observed, which was mainly due to calibration differences. The calibration variation has major clinical consequences, in particular in pediatrics, where reference ranges for serum and plasma creatinine are low, and in the estimation of glomerular filtration rate.

Clin Chem Lab Med 2008;46:1319–25.

Pulse pressure is an independent determinant of renal function decline during treatment of essential hypertension

BACKGROUND

In large epidemiological studies and using serum creatinine or estimates of glomerular filtration rate (GFR), blood pressure has emerged as a predominant determinant of the age-associated decline in renal function.

METHODS

The present longitudinal study (median follow-up period of 5.8 years) was conducted in 132 never-treated patients with essential hypertension at baseline. The effect of treatment on the GFR and effective renal plasma flow, estimated by urinary clearances of isotopic markers, was assessed.

RESULTS

Satisfactory control of hypertension (<140/90 mmHg) was achieved in 57% of the population. During follow-up, the yearly change in the GFR was -1.72+/-0.21 ml/min per year (mean+/-SEM). In univariate regression analysis, the change in the GFR was correlated with baseline pulse pressure (r=-0.27, P=0.002), whereas no influence of systolic, diastolic or mean blood pressures, as well as baseline albuminuria or left ventricular mass index, was found. Multivariate logistic regression analysis showed that only baseline pulse pressure conveyed a significant odds ratio of accelerated decline of GFR (>median of 1.5 ml/min per year), independently of age, baseline GFR, mean blood pressure and other known cardiovascular risk factors. No influence of the type of antihypertensive treatment (64% of the population had received angiotensin-converting enzyme inhibitor) was detected.

CONCLUSION

Pulse pressure (a marker of arterial stiffening) is suggested as an independent determinant of the treatment-associated decline in renal function in essential hypertension. No influence of target organ damage (albuminuria of left ventricular hypertrophy) was detected.

Measures of renal function, BMD, bone loss, and osteoporotic fracture in older adults: the Rancho Bernardo study

The association between bone and renal function in healthy seniors is not well studied. In this cross-sectional and longitudinal study in 1713 older men and women, creatinine clearance was significantly associated with hip BMD. If confirmed, this may warrant adding mild to moderate renal dysfunction as an indication for osteoporosis screening.

INTRODUCTION

This study determined the cross-sectional and longitudinal association between measures of renal function and BMD, bone loss, and osteoporotic fracture in older adults. It determined which measure of renal function--creatinine clearance by the Cockcroft-Gault (CG) equation, estimated glomerular filtration rate by the Modification of Diet in Renal Disease (MDRD) equation, or serum creatinine--is most strongly associated with BMD and osteoporotic fracture.

MATERIALS AND METHODS

This was a cross-sectional and prospective study in older community-dwelling men and women. Between 1992 and 1995, 1713 participants (average age, 71.3 +/- 11.1 years) completed standardized questionnaires, physical examinations, laboratory testing, and bone densitometry; 1023 participants returned for a follow-up visit in 1997-1999, an average of 4.1 +/- 0.9 years later.

RESULTS

Calculated renal function declined with age (p < 0.001). Renal function was categorized by Kidney Disease Outcomes Quality Initiative (K/DOQI) chronic kidney disease (CKD) stage. By the CG equation, at baseline, 5.5% of participants had stage 1 CKD (glomerular filtration rate > or = 90 ml/min/1.73 m(2)), 43.0% had stage 2 CKD (60-89 ml/min/1.73 m(2)), 48.8% had stage 3 CKD (30-59 ml/min/1.73 m(2)), and 2.7% had stages 4 and 5 CKD (<30 ml/min/1.73 m(2)). Using the MDRD equation, these percents were 7.0%, 61.7%, 30.9%, and 0.5%, respectively. In cross-sectional analyses, there was a significant linear association between creatinine clearance by CG or glomerular filtration rate by MDRD and hip BMD. In prospective analyses, there was an average annual bone loss of 0.6% and a significant association between baseline CG and 4-year hip bone loss. There was no association between baseline MDRD or serum creatinine and bone loss. At baseline, 180 of 1713 participants (11%) reported at least one clinical fracture of the hip, femur, forearm, or wrist; 79 (8%) reported new clinical fractures during follow-up. Baseline renal function by any measure was not significantly associated with prevalent or incident clinical fractures.

CONCLUSIONS

Although renal function measured by both CG and MDRD was associated with BMD in cross-sectional analyses, only creatinine clearance by CG predicted 4-year bone loss. If confirmed, this should be the preferred method for assessing the association between renal function and BMD. Cross-sectional associations between renal function and BMD were strongest at higher CKD stage. None of the baseline renal function estimates was associated with prevalent or incident fractures, perhaps reflecting the multifactorial etiology of fractures beyond BMD. If further studies in the elderly confirm renal function as an important predictor of bone loss and fracture, this may warrant adding mild to moderate renal dysfunction as an indication for osteoporosis screening.

Acute renal failure in the elderly: particular characteristics

Elderly individuals comprise the faster growing patient population group and acute renal failure (ARF) is quite common among them, although exact numbers are not known. We reviewed the literature with regards to the characteristics of ARF in elderly patients and describe some useful guidelines. The ageing kidney is characterized by many structural and functional changes, which are mainly due to various chronic disorders, such as hypertension, diabetes and atherosclerosis, which are highly prevalent in these patients. A number of structural and functional changes characteristic of the ageing kidney make elderly people especially prone to renal damage. ARF in the elderly is frequently of multifactorial origin and often with an atypical presentation, like the "intermediate syndrome", which combines characteristics of pre-renal azotemia and acute tubular necrosis. Physical examination and laboratory blood and urine indices may sometimes be misleading occasionally leading to misdiagnosis. Prophylaxis remains the preferred approach to therapy: one should avoid nephrotoxic drugs and poly-pharmacy, adjust drug doses and achieve adequate hydration of the patient as cautiously as possible. Dialysis therapies can be used for treatment of ARF irrespective of age and carry a good prognosis.

Prophylactic hemodialysis does not prevent contrast-induced nephropathy after cardiac catheterization in patients with chronic renal insufficiency

BACKGROUND

In Japan, prophylactic hemodialysis has been considered useful for preventing contrast-induced nephropathy (CIN).

METHOD AND RESULTS

To assess whether hemodialysis prevented CIN, 391 patients (age: 69 +/- 8 years, 63 females) with chronic renal insufficiency (CRI, serum creatinine level (Scr) > or = 1.3 mg/dl) who underwent cardiac catheterization, were retrospectively analyzed. Patients were divided into 3 categories based on Scr: L (1.3 > or = Scr < 2.0 mg/dl, n = 332); M (2.0 > or = Scr < 3.0 mg/dl, n = 49); and H (Scr > or = 3.0 mg/dl, n = 10). To prevent CIN, 35 category M patients and all category L patients received hydration alone, whereas 14 category M patients and all category H patients received hemodialysis. CIN developed in 48 patients. The incidence of CIN in category H was significantly higher than that in category L or M (H, 40% vs L, 11% or M, 16% (p < 0.05)). In category M patients treated with hemodialysis, Scr increased from 2.4 +/- 0.3 to 3.0 +/- 0.5 mg/dl (p < 0.05) within 7 days, and 29% of patients developed CIN. However, in category M patients who did not receive hemodialysis, the Scr did not change (pre, 2.3 +/- 0.2 mg/dl to post, 2.2 +/- 0.4 mg/dl), and the incidence of CIN was 11%.

CONCLUSION

Prophylactic hemodialysis for CRI patients undergoing cardiac catheterization does not prevent CIN.

Multifactorial approach and superior treatment efficacy in renal patients with the aid of nurse practitioners. Design of The MASTERPLAN Study [ISRCTN73187232]

BACKGROUND

Patients with chronic kidney disease (CKD) are at a greatly increased risk of developing cardiovascular disease. Recently developed guidelines address multiple risk factors and life-style interventions. However, in current practice few patients reach their targets.A multifactorial approach with the aid of nurse practitioners was effective in achieving treatment goals and reducing vascular events in patients with diabetes mellitus and in patients with heart failure. We propose that this also holds for the CKD population.

DESIGN

MASTERPLAN is a multicenter randomized controlled clinical trial designed to evaluate whether a multifactorial approach with the aid of nurse-practicioners reduces cardiovascular risk in patients with CKD. Approximately 800 patients with a creatinine clearance (estimated by Cockcroft-Gault) between 20 to 70 ml/min, will be included. To all patients the same set of guidelines will be applied and specific cardioprotective medication will be prescribed. In the intervention group the nurse practitioner will provide lifestyle advice and actively address treatment goals. Follow-up will be five years. Primary endpoint is the composite of myocardial infarction, stroke and cardiovascular mortality. Secondary endpoints are cardiovascular morbidity, overall mortality, decline of renal function, change in markers of vascular damage and change in quality of life. Enrollment has started in April 2004 and the study is on track with 700 patients included on October 15th, 2005. This article describes the design of the MASTERPLAN study.

[Creatinine clearance and drug prescriptions for the elderly. A study of 419 patients older than 70 years admitted through the emergency department]

INTRODUCTION

The incidence of drug-related adverse events increases with age. In approximately 20% of cases, these events necessitate hospitalization. By taking into account the physiological changes associated with aging when prescribing drugs, physicians can prevent some of these events. The objective of this study was to analyze the prescriptions written by general practitioners for elderly patients admitted to the emergency department in relation to the patient's creatinine clearance.

PATIENTS AND METHODS

Of 968 consecutive patients older than 70 years, 419 underwent a plasma creatinine assay on admission and were included in this study. Creatinine clearance was calculated with Cockcroft's formula. The patients were classified into two groups according to creatinine clearance:<30 mL/min (group I) and >or=30 mL/min (group II).

RESULTS

Creatinine clearance was<30 mL/min in 84 of the 419 patients (group I) and >or=30 mL/min in 335 (group II). Mean age was significantly higher in group I than in group II (87 +/- 6 vs 81 +/- 6 years, p<0.001), as was mean plasma creatinine concentration (113 +/- 23 vs 83 +/- 19 mmol/L, p<0.001), while mean weight was significantly lower (57 +/- 10 vs 69 +/- 13 kg, p<0.001. In group I, 82 drugs with precautions concerning renal function had been prescribed for 69 (82%) patients, and in group II, 331 such drugs for 174 (52%) patients. Of the 82 drugs prescribed in group I that required precaution, 47 (57%) were contraindicated or prescribed at an inappropriate dose in view of the creatinine clearance. Irrespective of pharmacokinetic parameters, the mean number of drugs taken per patient was 5 +/- 2 in group I and 6 +/-2 in group II.

CONCLUSION

In prescribing drugs for elderly patients, especially those whose weight is low, careful attention should be paid to renal function.

Antibiotic abscess penetration: fosfomycin levels measured in pus and simulated concentration-time profiles

The present study was performed to evaluate the ability of fosfomycin, a broad-spectrum antibiotic, to penetrate into abscess fluid. Twelve patients scheduled for surgical or computer tomography-guided abscess drainage received a single intravenous dose of 8 g of fosfomycin. The fosfomycin concentrations in plasma over time and in pus upon drainage were determined. A pharmacokinetic model was developed to estimate the concentration-time profile of fosfomycin in pus. Individual fosfomycin concentrations in abscess fluid at drainage varied substantially, ranging from below the limit of detection up to 168 mg/liter. The fosfomycin concentrations in pus of the study population correlated neither with plasma levels nor with the individual ratios of abscess surface area to volume. This finding was attributed to highly variable abscess permeability. The average concentration in pus was calculated to be 182 +/- 64 mg/liter at steady state, exceeding the MIC(50/90)s of several bacterial species which are commonly involved in abscess formation, such as streptococci, staphylococci, and Escherichia coli. Hereby, the exceptionally long mean half-life of fosfomycin of 32 +/- 39 h in abscess fluid may favor its antimicrobial effect because fosfomycin exerts time-dependent killing. After an initial loading dose of 10 to 12 g, fosfomycin should be administered at doses of 8 g three times per day to reach sufficient concentrations in abscess fluid and plasma. Applying this dosing regimen, fosfomycin levels in abscess fluid are expected to be effective after multiple doses in most patients.

5-Aminosalicylates and effects on renal function in patients with Crohn's disease

BACKGROUND

Case reports concerning irreversible renal failure caused by 5-aminosalicylates (5-ASA) have been published. The aim of this study was to investigate the effect of long-term use of 5-ASA on renal function in patients with Crohn's disease (CD).

METHODS

This was a retrospective survey in 200 consecutive outpatients with CD. Endogenous creatinine clearance (ECC) was estimated from serum creatinine with the Cockroft and Gault formula. The first ECC was chosen close to the start of 5-ASA and the second was the most recent ECC available.

RESULTS

In 153 patients (59 men and 94 women), sufficient data were available for analysis. The interval between ECCs was 11 years, with a mean exposure to 5-ASA of 8.6 years. The cumulative dose of 5-ASA amounted to 9 kg. The ECC declined 0.3 +/- 5 mL/min/yr (from 100 +/- 25 to 92 +/- 28 mL/min; P < 0.01). In a multiple linear regression model, duration of the interval was a significant predictor for change in ECC (P < 0.0001), but cumulative dose of 5-ASA was not predictive (P = 0.30). No interstitial nephritis was reported, and in the 8 patients with the largest decline in ECC, comorbidity causing renal function impairment was present.

CONCLUSIONS

The mean decline in ECC of 0.3 mL/min/yr in patients with CD does not exceed the decline expected from physiologic aging. Furthermore, the cumulative dose of 5-ASA was not a predictor for change in renal function. However, as interstitial nephritis caused by 5-ASA may rarely occur, we still advocate measurements of serum creatinine before and during treatment.

Screening techniques for detecting chronic kidney disease

PURPOSE OF REVIEW

As patients with impaired kidney function are at increased risk not only for progressive renal function loss, but also for cardiovascular disease, it is of importance to have accurate techniques to screen patients for the presence of an impaired kidney function.

RECENT FINDINGS

Glomerular filtration rate can in mass screenings best be evaluated using a formula based upon a serum creatinine measurement and anthropometric parameters. The Cockcroft-Gault and Modification of Diet in Renal Disease (MDRD) formulas are mostly used. Both are easy to use, but have their limitations. Interpreting the results of such glomerular filtration rate estimates requires a good knowledge of these limitations. Urinary albumin excretion can best be measured from 24 h urine collections. As these collections are difficult to perform, however, an early morning spot urine sample for the measurement of urinary albumin concentration can be applied as preselection for screening purposes.

SUMMARY

Mass screening for early kidney function impairment, expressed by an impaired glomerular filtration rate or elevated urinary albumin excretion, may help to detect patients at increased cardiac and renal risk. This can best be done using formulas to estimate glomerular filtration rate and by measuring urinary albumin loss.

Predictive performance of renal function equations in renal transplant recipients: an analysis of patient factors in bias

Creatinine-based equations are available to estimate GFR. After renal transplantation body composition usually changes, thus specific validation is required for transplant recipients. Nine equations were compared with iothalamate glomerular filtration rate (GFR) at 1 year after transplantation in 798 recipients. Equations were analyzed for precision, bias and accuracy. Sources of bias were analyzed by univariate and multivariate analysis, with body mass index (BMI), age and sex as independent variables and bias as dependent variable. Four hundred and seventy-eight patients were studied to assess whether the equations can be used to monitor renal function over time. Predictive performance was modest for all equations. MDRD and Jelliffe 2 were the best predictors of GFR. Bias was significantly related to BMI, age and gender in most equations. Multivariate analysis confirmed their independent contribution to the bias of MDRD, Jelliffe 2 and most other equations. Over time, bias was relatively stable at group level, but predictive performance in individuals was modest. The predictive performance of renal function equations is modest in renal transplants, which hampers their use for accurate assessment of renal function in the individual. The role of patient factors in the systematic error suggests that development of better equations should be feasible by better incorporation of these factors.

Incidence of renal insufficiency in cancer patients

The frequency of chronic renal insufficiency among cancer patients is unclear. The aim of this study was to determine the frequency of impaired renal function within a population of cancer patients. One thousand two hundred seventeen patients (563 women, 654 men) with cancer underwent serum creatinine concentration and glomerular filtration rate (GFR) evaluations. The Cockcroft-Gault formula was used to estimate the GFR from the creatinine clearance (Cl(cr)). Renal insufficiency was defined as a GFR <or=90 mL/min. Among this population, 72 (5.9%) demonstrated an abnormal serum creatinine concentration (>1.2 mg/dL). According to the Cockcroft-Gault formula evaluations, however, 330 (27.1%) of the patients had an estimated GFR <90 mL/min. Among these, the Clcr was between 60 and 89 mL/min in 241 patients (19.8%); 30 and 59 mL/min in 75 patients (6.2%); and 15 and 29 mL/min in 7 patients (0.6%); 7 patients (6%) had a Cl(cr) <15 mL/min. As a result, 21.2% of patients demonstrating a normal serum creatinine level had abnormal renal function. Renal function should be evaluated in all cancer patients, regardless of their serum creatinine level, before any drug regimen is administered. The Cockcroft-Gault formula appears to be more accurate than serum creatinine concentration for diagnosing renal insufficiency in patients with cancer, but more prospective studies in this population will be necessary to confirm this finding.

Pharmacokinetics and pharmacodynamics of cefpirome in subcutaneous adipose tissue of septic patients

The objective of the present study was to evaluate whether cefpirome, a member of the latest class of broad-spectrum cephalosporins, sufficiently penetrates subcutaneous adipose tissue in septic patients. After the administration of the drug at 2 g, tissue cefpirome concentrations in septic patients (n = 11) and healthy controls (n = 7) were determined over a period of 4 h by means of microdialysis. To assess the antibacterial effect of cefpirome at the target site, the measured pharmacokinetic profiles were simulated in vitro with select strains of Staphylococcus aureus and Pseudomonas aeruginosa. The tissue penetration of cefpirome was significantly impaired in septic patients compared with that in healthy subjects. For subcutaneous adipose tissue, the area under the concentration-versus-time curve values from 0 to 240 min were 13.11 +/- 5.20 g . min/liter in healthy subjects and 6.90 +/- 2.56 g . min/liter in septic patients (P < 0.05). Effective bacterial growth inhibition was observed in all in vitro simulations. This was attributed to the significantly prolonged half-life in tissue (P < 0.05), which kept the tissue cefpirome levels above the MICs for relevant pathogens for extended periods in the septic group. By consideration of a dosing interval of 8 h, the values for the time above MIC (T > MIC) in tissue were greater than 60% for pathogens for which the MIC was Collapse

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MESH Headings

• Adipose Tissue/metabolism
• Adult
• Area Under Curve
• Cephalosporins/adverse effects
• Cephalosporins/pharmacokinetics
• Chromatography, Micellar Electrokinetic Capillary
• Colony Count, Microbial
• Female
• Humans
• Male
• Microbial Sensitivity Tests
• Microdialysis
• Pseudomonas aeruginosa/drug effects
• Sepsis/metabolism
• Staphylococcus aureus/drug effects
• Cefpirome

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Affiliation(s)

Robert Sauermann Department of Clinical Pharmacology, Division of Clinical Pharmacokinetics, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
Georg Delle-Karth
Claudia Marsik
Ilka Steiner
Markus Zeitlinger
Bernhard X Mayer-Helm
Apostolos Georgopoulos
Markus Müller
Christian Joukhadar

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Trace microalbuminuria in inflammatory cystoid macular edema

PURPOSE

To assess the role of cardiovascular morbidity, its risk factors, and microalbuminuria in the development of inflammatory cystoid macular edema (CME).

DESIGN

A matched case-control study.

METHODS

study population: We included 24 consecutive patients with uveitis and CME. Twenty four uveitis patients without CME, matched for age and duration of uveitis served as controls. intervention and observation procedures: Patients and controls were interviewed for the presence of cardiovascular risk factors and cardiovascular morbidity. All medications were registered. Morning urinary albumin concentration was measured, as well as blood pressure, C-reactive protein, and creatinine in blood. Patients suffering from diabetes mellitus were excluded from this study. main outcome measures: The presence of cardiovascular morbidity and its risk factors and microalbuminuria in uveitis patients with and without CME.

RESULTS

We found a positive association between trace- and/or microalbuminuria and inflammatory CME (P = .001; odds ratio 13.0, 95% CI 2.5 to 68.1 and P = .015; odds ratio 5.9, 95% CI 1.6 to 22.6), but no relation between CME and cardiovascular morbidity or its risk factors. No additional association between trace- and/or any microalbuminuria and general characteristics of patients, specific factors related to general disease as a cause of ocular inflammation, location of uveitis, duration of uveitis, and medication was found.

CONCLUSIONS

The presence of trace- and/or microalbuminuria in inflammatory CME might indicate the presence of early systemic vascular disease and carry the risk of developing CME. This finding brings new insight into the pathogenesis of CME and could open up new avenues for the treatment of CME.

Performance of different prediction equations for estimating renal function in kidney transplantation

Numerous formulas have been developed to estimate renal function from biochemical, demographic and anthropometric data. Here we compared renal function derived from 12 published prediction equations with glomerular filtration rate (GFR) measurement by plasma iohexol clearance as reference method in a group of 81 renal transplant recipients enrolled in the Mycophenolate Mofetil Steroid Sparing (MY.S.S.) trial. Iohexol clearances and prediction equations were carried out in all patients at months 6, 9 and 21 after surgery. All equations showed a tendency toward GFR over-estimation: Walser and MDRD equations gave the best performance, however not more than 45% of estimated values were within +/-10% error. These formulas showed also the lowest bias and the highest precision: 0.5 and 9.2 mL/min/1.73 m2 (Walser), 2.7 and 10.4 mL/min/1.73 m2 (MDRD) in predicting GFR. A significantly higher rate of GFR decline ranging from -5.0 mL/min/1.73 m2/year (Walser) to -7.4 mL/min/1.73 m2/year (Davis-Chandler) was estimated by all the equations as compared with iohexol clearance (-3.0 mL/min/1.73 m2/year). The 12 prediction equations do not allow a rigorous assessment of renal function in kidney transplant recipients. In clinical trials of kidney transplantation, graft function should be preferably monitored using a reference method of GFR measurement, such as iohexol plasma clearance.

Estimation of glomerular filtration rate in the elderly: a comparison of creatinine-based formulae with serum cystatin C

OBJECTIVES

To estimate the prevalence of decreased kidney function in an elderly population and to evaluate the impact of using alternative markers of glomerular filtration rate (GFR), focusing on serum cystatin C (Cys C) and the Modification of Diet in Renal Disease (MDRD) Study prediction equation.

DESIGN AND METHODS

In a cross-sectional community-based survey renal function was assessed by serum creatinine (SCreat), Cys C and GFR predicted by the Cockcroft-Gault (CG) and the MDRD Study formulae. Associations with age, gender and proteinuria were analysed by linear models.

SUBJECTS

A total of 1246 elderly residents in Lieto, Finland, 64-100 years of age.

RESULTS

The prevalence of moderately or severely decreased renal function, estimated by the MDRD Study equation, was 35.7%; the CG formula yielded 58.6%. The profile of Cys C performance, including variation across age groups and level of health status, showed greater similarity to GFR estimated using the MDRD Study equation than to SCreat alone, or GFR estimated using the CG formula. Discordance between high Cys C levels and only mildly decreased GFR estimates was observed in subjects with functional limitations. Microalbuminuria was associated with Cys C levels only (P =0.047).

CONCLUSION

Prevalence estimates of decreased renal function amongst the elderly vary considerably depending on prediction formula used. Variation in creatinine metabolism amongst elderly comorbid patients and the critical dependence on the SCreat assay and exact calibration, make the use of creatinine-based formulae to predict GFR questionable in geriatric clinical practice. In this setting, Cys C is a promising alternative.

Can creatinine clearance be accurately predicted by formulae in octogenarian in-patients?

BACKGROUND

As serum creatinine is relatively inaccurate for estimating renal function, prediction formulae are commonly used for more precise renal function estimation. However, these equations have not been studied in acutely hospitalized octogenarian patients.

AIM

To compare three commonly used formulae for estimating GFR to measured creatinine clearance (CCR) in patients aged >/=80 years admitted to an acute geriatric department.

DESIGN

Prospective, observational study.

METHODS

Consecutive patients aged >/=80 years with urinary catheters, admitted over a 12-month period to the acute geriatric ward of a 600-bed university hospital, were enrolled in the study. All had an accurate 24-h urinary collection, as well as serum and urinary urea and creatinine determinations. CCR was calculated and compared with GFRs derived from the three formulae.

RESULTS

Of the 154 patients enrolled in the study, 107 (69.5%) had normal serum creatinine (</=1.4 mg/dl), but 77/107 (50.0%) of these had measured CCR </=60 ml/min/1.73 m(2). Mean CCR was 45.1 ml/min/1.73 m(2) declining at the rate of 1.1 ml/min/1.73 m(2) each year. Only 9% of patients according to the Cockcroft and Jelliffe formulae, and 17% by the MDRD formula, fell within -10% and +10% of the measured CCR, which were the limits of agreement decided prior to the initiation of the study.

DISCUSSION

Many elderly in-patients with moderate renal dysfunction will remain misidentified by relying on serum creatinine or commonly used prediction equations. The best practical approach in these patients is to avoid potentially nephrotoxic drugs and drugs excreted mainly through the kidneys.

Cystatin C vs creatinine as markers of renal function in patients on digoxin treatment

BACKGROUND

The kidney function is a major determinant of the serum concentration of digoxin as this drug is mainly eliminated unchanged through the kidneys. Since digoxin is widely prescribed among the elderly, and the glomerular filtration rate (GFR) declines with age, it is important that the clinician takes the patient's GFR into account when prescribing digoxin. Serum cystatin C has been suggested to be superior to creatinine for estimation of GFR, which may have relevance for the optimization of treatment with digoxin.

METHODS

To evaluate which of the two GFR markers serum creatinine and serum cystatin C that best correlates with serum digoxin, we compared the serum levels of digoxin with the serum levels of creatinine and cystatin C in 149 patients on therapeutic drug monitoring of digoxin at our hospital.

RESULTS

Overall, there was a stronger correlation between serum digoxin concentrations and cystatin C (p=0.00001) as compared to creatinine (p= 0.00003). Interestingly, of the patients with a serum digoxin concentration > or = 1.5 nmol/L, 29% had a serum creatinine level within normal limits, as compared to 20% with normal cystatin C levels.

CONCLUSIONS

In this study, serum cystatin C correlated better to serum digoxin than did serum creatinine. With improved GFR monitoring, digoxin concentrations should be better controlled.