Chronic kidney disease and automatic reporting of estimated glomerular filtration rate: a position statement

A pipeline to further enhance quality, integrity and reusability of the NCCID clinical data

The National COVID-19 Chest Imaging Database (NCCID) is a centralized UK database of thoracic imaging and corresponding clinical data. It is made available by the National Health Service Artificial Intelligence (NHS AI) Lab to support the development of machine learning tools focused on Coronavirus Disease 2019 (COVID-19). A bespoke cleaning pipeline for NCCID, developed by the NHSx, was introduced in 2021. We present an extension to the original cleaning pipeline for the clinical data of the database. It has been adjusted to correct additional systematic inconsistencies in the raw data such as patient sex, oxygen levels and date values. The most important changes will be discussed in this paper, whilst the code and further explanations are made publicly available on GitLab. The suggested cleaning will allow global users to work with more consistent data for the development of machine learning tools without being an expert. In addition, it highlights some of the challenges when working with clinical multi-center data and includes recommendations for similar future initiatives.

Can patterns of medication use explain the increasing incidence of end stage kidney disease among people with diabetes in Australia?

AIMS

Recently, an increase in the incidence of end-stage kidney disease (ESKD) among people with type 2 diabetes (T2D) aged < 50 years and ≥ 80 years has been observed in Australia. We examined whether patterns of medication use are likely to explain these trends.

METHODS

Among National Diabetes Services Scheme registrants, we determined the annual prevalence of dispensed glucose-lowering (GL), blood-pressure-lowering (BPL) and lipid-lowering (LL) agents with ≥3, ≥6 or ≥9 dispensings per year from 2003 to 2013. Relative changes in the prevalence were determined via Poisson regression.

RESULTS

During 2003-2013, the percentage of people with T2D dispensed GL, BPL and LL agents with ≥3, ≥6 or ≥9 dispensings per year increased in all age-groups. From 2003 to 2013, GL, BPL and LL agents use with ≥3 dispensings per year increased by 17%, 8.2%, and 53%, respectively. The use of renin-angiotensin-aldosterone-system-blockers over time also increased but more slowly in those aged <60 years compared to those aged ≥80 years (6% vs 18%, p < 0.001).

CONCLUSIONS

Changes in medication use are not likely to explain increasing incidence of ESKD in younger Australians with T2D. Studies are needed to provide insights into the major drivers of the rising incidence of ESKD in this population.

Effect of differences in serum creatinine estimation methodologies on estimated glomerular filtration rate

INTRODUCTION

Serum creatinine is crucial in glomerular filtration rate (GFR) estimation. Various methods of measuring GFR have been developed, which vary in their ability to estimate the prevalence of chronic kidney disease (CKD) and predict consequences associated with CKD. The use of different laboratory devices also results in uncertainty in estimated GFR (eGFR). The purpose of our study was to discuss the effect of differences in laboratory devices on eGFR when performing serum creatinine measurements.

METHODS

163 participants aged 51.22 ± 18.66 years were enrolled during a community health screening programme conducted on 18 June 2011. Samples were sent to four different hospitals using four different devices to check serum creatinine by the Jaffe and enzymatic creatinine methods.

RESULTS

Using Roche Cobas Integra 400, Beckman LX20, Hitachi 7180 and Toshiba TBA - c8000, the proportion of the population with eGFR < 60 mL/min/1.73 m² was 11.04%, 6.75%, 20.25% and 20.86%, respectively. Moreover, 3.68% of the participants had eGFR < 60 mL/min/1.73 m² in the laboratory when Roche Cobas Integra 400 was used with the enzymatic creatinine method and compensated Jaffe method.

CONCLUSION

Although standardisation of serum creatinine measurement has been achieved by using isotope dilution mass spectrometry, differences in measurement devices still cause substantial bias in the overall results. This affects the application of GFR in the estimation of CKD progression and outcomes associated with CKD.

Chronic kidney disease, Queensland: Profile of patients with chronic kidney disease from regional Queensland, Australia: A registry report

BACKGROUND

Chronic kidney disease, Queensland (CKD.QLD) is a multidisciplinary, collaborative research platform for CKD in Queensland. Most public renal services contribute towards the CKD Registry, including Toowoomba Hospital, which is a referral hospital for Darling Downs Health serving a largely regional population in Queensland. We aim to present the profile of the CKD cohort recruited to the CKD.QLD Registry from Toowoomba Hospital, the first comprehensive report on a pre-dialysis population from regional Australia.

METHODS

Study subjects were patients in the Darling Downs Health Service who consented to be included in the CKD.QLD registry from June 2011 to December 2016. Those who were on renal replacement therapy (RRT) were excluded. Patients were followed until date of RRT, death, discharge or loss to follow up or a censor date of 30th June 2017.

RESULTS

Overall 1051 subjects, representing 13% of all CKD.QLD Registry patients gave consent of whom, 42.7% were ≥70 years of age. The mean age was 63.8 ± 15.1 years (median age 67 years) with male predominance (55.4%). The majority were born in Australia (86.4%). Aboriginal and Torre Strait Islanders (A&TSI) constituted 9.6% of the cohort. The predominant CKD stages were 3b (28.9%) and 4 (27.7%). Hypertension and diabetes were noted in 91% and 44% of subjects, respectively. Diabetic nephropathy was the leading cause of CKD (26.7%) followed by renovascular disease (17.3%) and glomerulonephritis (14.8%). In 12%, the diagnosis was uncertain. Major co-morbidities included coronary artery disease (24.7%) chronic lung disease (14.8%), cerebrovascular disease (11.6%) and peripheral vascular disease (8.9%). Non-vascular co-morbidities included arthritis (24.6%), gout (23.6%) and gastro-oesophageal reflux disease (19%). The multi-morbidity profile was differed by gender, diabetic status and age. Over a follow-up period upto 72 months, 93 (8.8%) started RRT and 175 (16.6%) died. Of those 82% died without RRT and 18% died after RRT.

CONCLUSION

This CKD Registry cohort from regional Queensland consisted mainly of older Caucasians with male predominance. A&TSI patients were overrepresented compared to the overall population. A significant proportion had cardio-vascular disease and multiple co-morbidities which differed by gender, diabetic status and age. This report provides valuable data for health services planning and delivery in regional Queensland.

Incidence and Impact of Hypoalbuminaemia on Outcomes Following Acute Pulmonary Embolism

BACKGROUND

Clinical features and outcomes of patients with hypoalbuminaemia in acute pulmonary embolism (PE) have never been studied. The present study investigated the incidence and determined the prognostic significance of hypoalbuminaemia in patients with confirmed acute PE.

METHODS

From a dedicated tertiary-referral centre database involving 1,426 consecutive patients admitted with confirmed PE (2000-2012), 1,032 patients had serum albumin assessed on admission (day-1). Patients were stratified into hypoalbuminaemia (<35 g/L) or normal serum albumin (≥35 g/L). Multivariable logistic and Cox proportional-hazards regression methods were used to assess 30-day and 90-day all-cause mortality.

RESULTS

Hypoalbuminaemia was present in 160 (15.5%) patients at day-1 and was associated with higher mean (±SD) heart rate (94.4 ± 21.8 vs 87.8 ± 21.5 bpm), lower systolic blood pressure (131.0 ± 24.7 vs 142.3 ± 24.7 mmHg), lower arterial oxyhaemoglobin saturation (93.3 ± 6.1% vs 95.6 ± 4.0%), lower day-1 serum sodium (137.0 ± 4.7 vs 138.8 ± 3.8 mmol/L) and haemoglobin levels (114.4 ± 20.7 vs 131.5 ± 18.7 g/L). Patients with hypoalbuminaemia had higher incidence of malignancy (44.4% vs 18.8%) and chronic renal disease (9.4% vs 5.2%), and at admission were less likely to be taking aspirin/clopidogrel (19.3% vs 27.7%) and more likely to be using enoxaparin (6.7% vs 3.0%). During a mean follow-up of 5.0 ± 4.0 years, patients with hypoalbuminaemia had higher 30-day (16.3% vs 3.6%) and 90-day (26.3% vs 6.2%) mortality. Multivariable analyses showed hypoalbuminaemia independently predicted both 30-day (odds ratio 2.57, 95% confidence interval [CI] 1.03-6.41) and 90-day (hazard ratio 2.42 95% CI 1.38-4.22) mortality.

CONCLUSION

Hypoalbuminaemia is an independent predictor of mortality following PE and may improve risk stratification of patients in risk prediction models.

Trends in Incidence of ESKD in People With Type 1 and Type 2 Diabetes in Australia, 2002-2013

RATIONALE & OBJECTIVE

The number of people with diabetes and end-stage kidney disease (ESKD) is increasing worldwide, but it is unknown whether this indicates an increasing risk for ESKD in people with diabetes. We examined temporal trends in the incidence of ESKD within the Australian population with diabetes from 2002 to 2013.

STUDY DESIGN

Follow-up study using a national health care services registry.

SETTING & PARTICIPANTS

Registrants with type 1 or type 2 diabetes in Australia's National Diabetes Services Scheme (NDSS).

PREDICTORS

Age, sex, indigenous status, diabetes type, and calendar year.

OUTCOME

Incidence of ESKD (dialysis or kidney transplantation) or death ascertained using the Australian and New Zealand Dialysis and Transplant Registry and the Australian national death index.

ANALYTICAL APPROACH

NDSS registrants were followed up from 2002 or date of registration until onset of ESKD, death, or December 31, 2013. The incidence of ESKD in type 1 diabetes was calculated only in those younger than 55 years.

RESULTS

Among 1,375,877 registrants between 2002 and 2013, a total of 9,977 experienced incident ESKD, representing an overall incidence of ESKD in people with diabetes of 10.0 (95% CI, 9.8-10.2) per 10,000 person-years. Among those with type 1 diabetes, the age-standardized annual incidence was stable during the study period. Among those with type 2 diabetes, the incidence increased in nonindigenous people (annual percentage change, 2.2%; 95% CI, 0.4%-4.1%) with the greatest increases in those younger than 50 and those older than 80 years. No significant change over time was observed in indigenous people, although the adjusted incident rate ratio for indigenous versus nonindigenous was 4.03 (95% CI, 3.68-4.41).

LIMITATIONS

Lack of covariates such as comorbid conditions, medication use, measures of quality of care, and baseline kidney function.

CONCLUSIONS

The age-standardized annual incidence of ESKD increased in Australia from 2002 to 2013 for nonindigenous people with type 2 diabetes but was stable for people with type 1 diabetes. Efforts to prevent the development of ESKD, especially among indigenous Australians and those with early-onset type 2 diabetes, are warranted.

Comparison of equations for dosing of medications in renal impairment

AIM

The aim of this study is to determine the concordance among the Cockcroft-Gault, the Modification of Diet in Renal Disease and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in hypothetical dosing of renally cleared medications.

METHODS

A total of 2163 patients prescribed at least one of the 31 renally cleared drugs under review were included in the study. Kidney function was estimated using the three equations. We compared actual prescribed dosages of the same drug with recommended dosages based on the kidney function as calculated by each of the equations and applying dosing recommendations in the Australian Medicines Handbook.

RESULTS

There was a significant difference in the kidney function values estimated from the three equations (P < 0.001). Despite the good overall agreement in renal drug dosing, we found selected but potentially important discrepancies among the doses rendered from the equations. The CKD-EPI equation non-normalized for body surface area had a greater rate of concordance with the Cockcroft-Gault equation than the Modification of Diet in Renal Disease equation for renal drug dosing.

CONCLUSIONS

There is need for a long-term multi-centre study in a diverse population to define the clinical effects of the discrepancies among the equations for drug dosing. Given the greater concordance of the non-normalized CKD-EPI equation with the Cockcroft-Gault equation for dosing, the recommendation by Kidney Health Australia and the United States National Kidney Disease Education Program that 'dosing based on either eCrCl or an eGFR with body surface area normalization removed are acceptable' seems suitable and practicable for the purpose of dosing of non-critical drugs in the primary care setting.

Acute pulmonary embolism during warfarin therapy and long-term risk of recurrent fatal pulmonary embolism

The clinical characteristics and long-term outcomes of patients presenting with acute pulmonary embolism (PE) during treatment with warfarin have not been described. Clinical details of all patients admitted to a tertiary institution from 2000-2007 with acute PE were retrieved retrospectively, baseline warfarin status and the international normalised ratio (INR) were recorded, and their outcomes tracked using a statewide death registry. Of 923 patients with clearly documented warfarin status included in this study, 83 (9%) were taking warfarin. Mean (± standard deviation) day-1 INR of those taking warfarin was 2.3 ± 0.9, with 67% of patients therapeutically anti-coagulated (INR ≥2.0) at presentation (49 patients with INR <2.5 and 34 with INR ≥2.5). Patients taking warfarin on admission were more likely to have heart failure, atrial fibrillation and valvular heart disease, with similar prevalence of malignancy and ischaemic heart disease, compared to patients not on warfarin. Total mortality of the cohort (mean follow-up 4.0 ± 2.5 years) was 31.6% (in-hospital mortality 1.5%), and was similar between warfarin and no warfarin groups. There was however a greater than four-fold increased risk of post-discharge death due to recurrent PE for the patients taking warfarin on admission (hazard ratio [HR] 4.43, 95% confidence interval [CI] 1.36-14.42, p=0.01). Among patients taking warfarin on admission, day-1 INR <2.5 significantly increased long-term all-cause mortality compared to INR ≥2.5 (adjusted HR 2.51, 95% CI 1.08-5.86, p=0.03). In conclusion, patients presenting with PE during treatment with warfarin have an increased risk of death from recurrent PE. Admission INR appears to have independent long-term prognostic importance in these patients.

CKD.QLD: establishment of a chronic kidney disease [CKD] registry in Queensland, Australia

Background

Chronic kidney disease [CKD] is recognised as a global public health problem. Until recently, the majority of information informing on CKD has been generated from renal registries reporting on patients with end-stage kidney disease [ESKD] and on renal replacement therapy [RRT]. There has been a paucity of information on pre-dialysis CKD cohorts, and many issues related to these poorly described populations are unresolved. To this end, international organizations have called for CKD surveillance systems across all countries.

Description

In Australia, we have responded by developing the Chronic Kidney Disease in Queensland [CKD.QLD] with three main platforms consisting of CKD Registry, clinical trials and development of biobank. This registry which is the core component of CKD surveillance was conceptualized specifically for the pre-dialysis population in the public health system in Queensland, Australia. Recruitment started in May 2011, and to date the Registry has evolved as one of the largest CKD cohorts in the world with recruitment close to 7000 patients. The Registry has had many outcomes, including being the nidus for Australia’s first National Health and Medical Research Council [NHMRC] CKD Centre of Research Excellence [CKD.CRE].

Conclusions

The Registry, with its linkage to Queensland Health datasets, is reporting, and is expected to continue generating, significant information on multiple aspects of CKD, its trajectory, management and patient outcomes. Intent of the CKD.CRE is to facilitate an expanded Registry network that has representation from health services, both public and private, across Australia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0607-5) contains supplementary material, which is available to authorized users.

Diabetic kidney disease: a role for advanced glycation end-product receptor 1 (AGE-R1)?

Diabetic patients are postulated to be in a perpetual state of oxidative stress and inflammation at sites where chronic complications occur. The accumulation of AGEs derived from both endogenous and exogenous sources (such as the diet) have been implicated in the development and progression of diabetic complications, particularly nephropathy. There has been some interest in investigating the potential for reducing the AGE burden in chronic disease, through the action of AGE "clearance" receptors, such as the advanced glycation end-product receptor 1 (AGE-R1). Reducing the burden of AGEs has been linked to attenuation of inflammation, slower progression of diabetic complications (in particular vascular and renal complications) and has been shown to extend lifespan. To date, however, there have been no direct investigations into whether AGE-R1 has any role in modulating normal kidney function, or specifically during the development and progression of diabetes. This mini-review will focus on the recent advances in knowledge around the mechanistic function of AGE-R1 and the implications of this for the pathogenesis of diabetic kidney disease.

Correlation between trough plasma dabigatran concentrations and estimates of glomerular filtration rate based on creatinine and cystatin C

AIMS

Dabigatran is largely cleared by renal excretion. Renal function is thus a major determinant of trough dabigatran concentrations, which correlate with the risk of thromboembolic and haemorrhagic outcomes. Current dabigatran dosing guidelines use the Cockcroft-Gault (CG) equation to gauge renal function, instead of contemporary equations including the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations employing creatinine (CKD-EPI_Cr), cystatin C (CKD-EPI_Cys) and both renal biomarkers (CKD-EPI_CrCys).

METHODS

A linear regression model including the dabigatran etexilate maintenance dose rate, relevant interacting drugs and genetic polymorphisms (including CES1), was used to analyse the relationship between the values from each renal function equation and trough steady-state plasma dabigatran concentrations.

RESULTS

The median dose-corrected trough steady-state plasma dabigatran concentration in 52 patients (38-94 years) taking dabigatran etexilate was 60 µg/L (range 9-279). The dose-corrected trough concentration in a patient on phenytoin and phenobarbitone was >3 standard deviations below the cohort mean. The CG, CKD-EPI_Cr, CKD-EPI_Cys and CKD-EPI_CrCys equations explained (R (2), 95 % CI) 32 % (9-55), 37 % (12-60), 41 % (16-64) and 47 % (20-69) of the variability in dabigatran concentrations between patients, respectively. One-way analysis of variance (ANOVA) comparing the R (2) values for each equation was not statistically significant (p = 0.74).

DISCUSSION

Estimates of renal function using the four equations accounted for 32-47 % of the variability in dabigatran concentrations between patients. We are the first to provide evidence that co-administration of phenytoin/phenobarbitone with dabigatran etexilate is associated with significantly reduced dabigatran exposure.

Is renal function associated with early age-related macular degeneration?

PURPOSE

Age-related macular degeneration (AMD) and chronic kidney disease both involve immune dysregulation and may share underlying pathophysiologic changes to systemic homeostasis. Hence, we aim to evaluate associations between impaired kidney function and early AMD, in a search for urinary biomarkers for AMD.

METHODS

A population-based, cross-sectional analysis of persons aged 45 to 84 years was conducted with renal function measured using serum creatinine and cystatin C levels and the estimated glomerular filtration rate (eGFR) calculated. Age-related macular degeneration status was ascertained from retinal photographs.

RESULTS

Of 5874 participants, 221 had early AMD. High serum cystatin C and low eGFR (≤60 ml/min/1.73 m) were not associated with early AMD in our multivariate analyses. Among normotensive persons, however, highest versus other deciles of cystatin C were associated with an increased prevalence of early AMD (odds ratio, 1.80; 95% confidence interval, 1.00 to 3.23).

CONCLUSIONS

Results could not confirm an association between kidney function and early AMD. The borderline association between cystatin C and early AMD in normotensive persons require further verification.

Dose adjustment guidelines for medications in patients with renal impairment: how consistent are drug information sources?

BACKGROUND

It is known that patients with renal disease are often administered inappropriate dosages of drugs. A lack of quantitative data in the available drug information sources and inconsistency in dosing information may augment the problem of dosing error.

AIMS

To determine the concordance among five drug information sources regarding the dosing recommendations provided for drugs considered problematic in patients with renal impairment and to determine the consistency among the sources regarding the definition of renal impairment and categorisation of chronic kidney disease.

METHODS

Five standard drug information sources were reviewed for 61 drugs recommended to be used with caution in renal impairment. Information on recommendations for dosage adjustment in renal impairment was extracted and analysed. Further, the definition and classification of renal impairment were recorded. The recommendation for each drug was coded into six different categories and the intersource reliability was calculated.

RESULTS

Only slight agreement was observed among the sources (Fleiss Kappa: 0.3). Qualitative data were not well defined, and there was a lack of consistency in quantitative values. Some drugs marked as contraindicated in one source were not mentioned as such in others. Also, drugs considered as not requiring dosage adjustment in one source had explicit recommendations in other sources. The definition and classification of renal impairment differed among the five information sources.

CONCLUSIONS

There should be an evidence-based approach to drug dosage adjustment in order to bring uniformity to the recommendations. Regular updating of the content of the drug information sources is also important.

Long-term complications and mortality in young-onset diabetes: type 2 diabetes is more hazardous and lethal than type 1 diabetes

OBJECTIVE

To evaluate long-term clinical outcomes and survival in young-onset type 2 diabetes (T2DM) compared with type 1 diabetes (T1DM) with a similar age of onset.

RESEARCH DESIGN AND METHODS

Records from the Royal Prince Alfred Hospital Diabetes Clinical Database, established in 1986, were matched with the Australian National Death Index to establish mortality outcomes for all subjects until June 2011. Clinical and mortality outcomes in 354 patients with T2DM, age of onset between 15 and 30 years (T2DM15-30), were compared with T1DM in several ways but primarily with 470 patients with T1DM with a similar age of onset (T1DM15-30) to minimize the confounding effect of age on outcome.

RESULTS

For a median observation period of 21.4 (interquartile range 14-30.7) and 23.4 (15.7-32.4) years for the T2DM and T1DM cohorts, respectively, 71 of 824 patients (8.6%) died. A significant mortality excess was noted in T2DM15-30 (11 vs. 6.8%, P = 0.03), with an increased hazard for death (hazard ratio 2.0 [95% CI 1.2-3.2], P = 0.003). Death for T2DM15-30 occurred after a significantly shorter disease duration (26.9 [18.1-36.0] vs. 36.5 [24.4-45.4] years, P = 0.01) and at a relatively young age. There were more cardiovascular deaths in T2DM15-30 (50 vs. 30%, P < 0.05). Despite equivalent glycemic control and shorter disease duration, the prevalence of albuminuria and less favorable cardiovascular risk factors were greater in the T2DM15-30 cohort, even soon after diabetes onset. Neuropathy scores and macrovascular complications were also increased in T2DM15-30 (P < 0.0001).

CONCLUSIONS

Young-onset T2DM is the more lethal phenotype of diabetes and is associated with a greater mortality, more diabetes complications, and unfavorable cardiovascular disease risk factors when compared with T1DM.

The performances of the Cockcroft-Gault, modification of diet in renal disease study and chronic kidney disease epidemiology collaboration equations in predicting gentamicin clearance

BACKGROUND

It is unclear which renal function equation, employing an isotope dilution mass spectrometry (IDMS)-aligned creatinine assay, best predicts gentamicin clearance.

METHODS

The performances of the Cockcroft-Gault, Modification of Diet in Renal Disease (MDRD) Study and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations for predicting gentamicin clearances were assessed retrospectively in 240 patients treated with gentamicin during 2011-2012, when the local creatinine assay was IDMS-aligned. Comparisons were based on the percentage within 30% of gentamicin clearance (P 30) and the root-mean-square error (RMSE) of each equation. Gentamicin clearance was calculated from plasma concentrations using a one-compartment model.

RESULTS

The Cockcroft-Gault equation and the CKD-EPI equation corrected for individual body surface area (BSA) were associated with the highest P 30 (69% and 67%, respectively) and lowest RMSE (39 and 36 mL/min, respectively) in the 240 patients. Correction for individual BSA improved the performances of the MDRD Study and CKD-EPI equations in patients with body mass indices <18.5 or ≥30 kg/m(2). The equations systematically underestimated gentamicin clearance as gentamicin clearance increased, with performance being inferior with gentamicin clearance ≥90 versus <90 mL/min.

CONCLUSIONS

The CKD-EPI equation corrected for individual BSA, and the Cockcroft-Gault equation, provided the best estimates of gentamicin clearance. The CKD-EPI and MDRD Study equations should be corrected for individual BSA at the extremes of body size, if used for guiding gentamicin therapy. The performances of the equations were inferior in patients with higher values of gentamicin clearance.

The impact of introducing automated eGFR reporting on uncovering new cases of chronic kidney disease in a University Hospital in Saudi Arabia

OBJECTIVE

To determine the impact of introducing eGFR automated reporting on uncovering new cases of Chronic Kidney Disease.

METHODS

All serum creatinine (SCr) in adult patients attending outpatient clinics over a two-month period were recorded and eGFR estimated. Cases with a SCr within normal limits but were in CKD stage 3 (<60 mL/min) or higher were recorded and their numbers, percentages and mean ages calculated. Stages 1 and 2 were excluded from analysis because urinary albumin and other urinary abnormalities were not checked.

RESULTS

A total of 26,422 SCr from different patients were included. The mean SCr was 92.5 ± 130.9 μmol/ and the mean eGFR was 99.8 ± 32.4 mL/min/1.73 m(2). Of all the10,601 males with normal SCr, 0.84% were in CKD stage 3 and in all the 14,695 female, 19.24% were in stage 2 in stage. Of all the 14,695 females with serum creatinine in the normal range, 200 (1.36%) were in CKD stage 3. The patients in stages 2 and 3 were significantly older.

CONCLUSION

If our findings are shown to be true for the rest of Saudi Arabia, one could extrapolate that for each 100,000 serum creatinine assayed for males, 840 new cases will be uncovered in CKD stage 3. The corresponding number for females would be 1360 cases.

Vancomycin AUC/MIC ratio and 30-day mortality in patients with Staphylococcus aureus bacteremia

A ratio of the vancomycin area under the concentration-time curve to the MIC (AUC/MIC) of ≥ 400 has been associated with clinical success when treating Staphylococcus aureus pneumonia, and this target was recommended by recently published vancomycin therapeutic monitoring consensus guidelines for treating all serious S. aureus infections. Here, vancomycin serum trough levels and vancomycin AUC/MIC were evaluated in a "real-world" context by following a cohort of 182 patients with S. aureus bacteremia (SAB) and analyzing these parameters within the critical first 96 h of vancomycin therapy. The median vancomycin trough level at this time point was 19.5 mg/liter. There was a significant difference in vancomycin AUC/MIC when using broth microdilution (BMD) compared with Etest MIC (medians of 436.1 and 271.5, respectively; P < 0.001). Obtaining the recommended vancomycin target AUC/MIC of ≥ 400 using BMD was not associated with lower 30-day all-cause or attributable mortality from SAB (P = 0.132 and P = 0.273, respectively). However, an alternative vancomycin AUC/MIC of >373, derived using classification and regression tree analysis, was associated with reduced mortality (P = 0.043) and remained significant in a multivariable model. This study demonstrated that we obtained vancomycin trough levels in the target therapeutic range early during the course of therapy and that obtaining a higher vancomycin AUC/MIC (in this case, >373) within 96 h was associated with reduced mortality. The MIC test method has a significant impact on vancomycin AUC/MIC estimation. Clinicians should be aware that the current target AUC/MIC of ≥ 400 was derived using the reference BMD method, so adjustments to this target need to be made when calculating AUC/MIC ratio using other MIC testing methods.

Case report of interstitial nephritis induced by bevacizumab therapy for glioblastoma multiforme

Glioblastoma multiforme is an aggressive malignant brain tumor. The monoclonal antibody, bevacizumab, is active in recurrent disease via inhibition of angiogenesis. Proteinuria and renal thrombotic microangiopathy are known complications. We report a case of a patient developing acute renal failure with biopsy-proven interstitial nephritis while receiving bevacizumab for recurrent disease. The patient was otherwise well with a history of controlled hypertension. Renal function improved with discontinuation of bevacizumab and the administration of corticosteroid therapy.

Chronic kidney disease and automatic reporting of estimated glomerular filtration rate: new developments and revised recommendations

The publication of the Australasian Creatinine Consensus Working Group's position statements in 2005 and 2007 resulted in automatic reporting of estimated glomerular filtration rate (eGFR) with requests for serum creatinine concentration in adults, facilitated the unification of units of measurement for creatinine and eGFR, and promoted the standardisation of assays. New advancements and continuing debate led the Australasian Creatinine Consensus Working Group to reconvene in 2010. The working group recommends that the method of calculating eGFR should be changed to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula, and that all laboratories should report eGFR values as a precise figure to at least 90 mL/min/1.73 m(2). Age-related decision points for eGFR in adults are not recommended, as although an eGFR < 60 mL/min/1.73 m(2) is very common in older people, it is nevertheless predictive of significantly increased risks of adverse clinical outcomes, and should not be considered a normal part of ageing.If using eGFR for drug dosing, body size should be considered, in addition to referring to the approved product information. For drugs with a narrow therapeutic index, therapeutic drug monitoring or a valid marker of drug effect should be used to individualise dosing. The CKD-EPI formula has been validated as a tool to estimate GFR in some populations of non-European ancestry living in Western countries. Pending publication of validation studies, the working group also recommends that Australasian laboratories continue to automatically report eGFR in Aboriginal and Torres Strait Islander peoples. The working group concluded that routine calculation of eGFR is not recommended in children and youth, or in pregnant women. Serum creatinine concentration (preferably using an enzymatic assay for paediatric patients) should remain as the standard test for kidney function in these populations.

Chronic kidney disease and measurement of albuminuria or proteinuria: a position statement

Optimal detection and subsequent risk stratification of people with chronic kidney disease (CKD) requires simultaneous consideration of both kidney function (glomerular filtration rate [GFR]) and kidney damage (as indicated by albuminuria or proteinuria). Measurement of urinary albuminuria and proteinuria is hindered by a lack of standardisation regarding requesting, sample collection, reporting and interpretation of tests. A multidisciplinary working group was convened with the goal of developing and promoting recommendations that achieve consensus on these issues. The working group recommended that the preferred method for assessment of albuminuria in both diabetic and non-diabetic patients is urinary albumin-to-creatinine ratio (UACR) measurement in a first-void spot urine specimen. Where a first-void specimen is not possible or practical, a random spot urine specimen for UACR is acceptable. The working group recommended that adults with one or more risk factors for CKD should be assessed using UACR and estimated GFR every 1-2 years, depending on their risk-factor profile. Recommended testing algorithms and sex-specific cut-points for microalbuminuria and macroalbuminuria are provided. The working group recommended that all pathology laboratories in Australia should implement the relevant recommendations as a vital component of an integrated national approach to detection of CKD.

Foxp3+ T cells in peripheral blood of renal transplant recipients and clinical correlations

AIM

Immunophenotype peripheral blood T cells from renal transplant recipients (RTR) using cellular markers of regulatory T cells (Tregs) and flow cytometry, including Foxp3, and correlate these findings with clinical parameters.

METHODS

Expression of phenotypic markers of Tregs was assessed by flow cytometric analysis of peripheral blood lymphocytes (PBL) from (i) RTR (n = 95); (ii) patients with end-stage renal failure (ESRF) awaiting transplantation (n = 17); and (iii) normal healthy controls (n = 18).

RESULTS

The percentage of CD4(+) CD25(+) Foxp3(+) cells within the CD4(+) cell population did not significantly alter at different time points post-transplant. However, the percentage of CD4(+) CD25(+) Foxp3(+) cells within the CD4(+) population was significantly lower in RTR compared with patients with ESRF. In contrast, RTR and ESRF had a similar percentage of CD4(+) CD25(+) cells expressing Foxp3. Multivariate analysis of PBL and clinical parameters demonstrated (i) a positive linear relationship between the percentage CD4(+) CD25(+) cells expressing Foxp3 and estimated glomerular filtration rate and (ii) a higher percentage of CD4(+) CD25(+) cells in the CD4(+) cell population in patients with malignancy (the majority were skin cancers). Malignancy also correlated strongly with time post-transplant and age of the RTR.

CONCLUSION

Immune monitoring of the PBL phenotype in RTR using CD4, CD25 and Foxp3 may stratify RTR and predict graft outcome and function, and risk of complications from immunosuppression. Longitudinal and functional studies of Tregs are essential to extend the findings of the present study.

Change in appropriate referrals to nephrologists after the introduction of automatic reporting of the estimated glomerular filtration rate

BACKGROUND

Use of the serum creatinine concentration, the most widely used marker of kidney function, has been associated with under-reporting of chronic kidney disease and late referral to nephrologists, especially among women and elderly people. To improve appropriateness of referrals, automatic reporting of the estimated glomerular filtration rate (eGFR) by laboratories was introduced in the province of Ontario, Canada, in March 2006. We hypothesized that such reporting, along with an ad hoc educational component for primary care physicians, would increase the number of appropriate referrals.

METHODS

We conducted a population-based before-after study with interrupted time-series analysis at a tertiary care centre. All referrals to nephrologists received at the centre during the year before and the year after automatic reporting of the eGFR was introduced were eligible for inclusion. We used regression analysis with autoregressive errors to evaluate whether such reporting by laboratories, along with ad hoc educational activities for primary care physicians, had an impact on the number and appropriateness of referrals to nephrologists.

RESULTS

A total of 2672 patients were included in the study. In the year after automatic reporting began, the number of referrals from primary care physicians increased by 80.6% (95% confidence interval [CI] 74.8% to 86.9%). The number of appropriate referrals increased by 43.2% (95% CI 38.0% to 48.2%). There was no significant change in the proportion of appropriate referrals between the two periods (-2.8%, 95% CI -26.4% to 43.4%). The proportion of elderly and female patients who were referred increased after reporting was introduced.

INTERPRETATION

The total number of referrals increased after automatic reporting of the eGFR began, especially among women and elderly people. The number of appropriate referrals also increased, but the proportion of appropriate referrals did not change significantly. Future research should be directed to understanding the reasons for inappropriate referral and to develop novel interventions for improving the referral process.

Cardiovascular risk management in chronic kidney disease in general practice (the AusHEART study)

BACKGROUND

Chronic kidney disease (CKD) is common and increasing in prevalence. Adverse outcomes of CKD can be prevented through early detection and treatment. There is limited data on the awareness of CKD and the quality of care offered to patients with CKD in the primary care setting. The objectives of this study were to assess the prevalence, general practitioner (GP) awareness and extent of current evidence-practice gaps in the management of CKD in Australian primary care.

METHODS

The Australian Hypertension and Absolute Risk Study (AusHEART) was a nationally representative, cluster stratified, cross-sectional survey among 322 GPs. Each GP was asked to provide data for 15-20 consecutive patients (age ≥ 55 years) who presented between April and June, 2008. The main outcome measures were CKD prevalence based on proteinuria and decreased estimated glomerular filtration rate. Evidence-practice gaps in management of patients with CKD were identified.

RESULTS

Among a total of 4966 patients with kidney function test data, 1845 (37%) had abnormal kidney function. Of the 1312 patients with abnormal kidney function known to the GP at the time of visit, only 235 were correctly identified as having CKD. GPs under-estimated cardiovascular (CV) risks in patients with CKD when compared with the prevailing guidelines at the time of survey and the recent national guidelines, particularly in later stages of CKD. Among CKD patients not prescribed blood pressure-lowering agents or lipid-lowering agents, treatment was indicated as per relevant guidelines in 51 and 46%, respectively. For CKD patients who were already prescribed blood pressure-lowering and lipid-lowering agents, 61 and 50%, respectively, did not meet the treatment targets recommended by the relevant guidelines.

CONCLUSIONS

CKD is common, significantly under-recognized and under-treated in primary care. Effort to increase awareness and provide opportunities for improved screening and assessment should improve the management and outcome of these patients at high risk of CV disease.

Evaluation of the accuracy of a pharmacokinetic dosing program in predicting serum vancomycin concentrations in critically ill patients

BACKGROUND

Optimization of the timing of appropriate antibiotics is crucial to improve the management of patients in severe sepsis and septic shock. Vancomycin is commonly used empirically in cases of nosocomial infections in critically ill patients. Therefore, early optimization of vancomycin pharmacokinetics is likely to improve outcomes.

OBJECTIVE

To evaluate a pharmacokinetic program to predict serum vancomycin concentrations in accordance with administered dose, weight, height, and creatinine clearance in a critically ill population.

METHODS

We conducted a prospective observational single-center study in a 45-bed intensive care unit (ICU). All patients hospitalized in the ICU requiring intravenous treatment with vancomycin for a suspected infection were enrolled. The modalities of vancomycin therapy and the monitoring of serum concentrations were left to the discretion of the treating clinician. We compared the measured serum vancomycin concentrations with those predicted by the MM-USCPACK program and analyzed the factors influencing the prediction.

RESULTS

Fifty-four intravenous vancomycin courses were administered in 48 critically ill patients over the 3-month study. The precision was considered acceptable, based on a relative precision equal to 8.9% (interquartile range 3.5-18.9%) and the relative bias for all predictions was equal to -1.3%. Overall, 77.3% of predictions were within 20% of observed concentrations; factors correlating with a poorer prediction were a change in renal function, obesity, and the magnitude of organ dysfunction on initiation of vancomycin (expressed by a Systemic Organ Failure Assessment score >11).

CONCLUSIONS

The MM-USCPACK program is a useful and reliable tool for prediction of serum vancomycin concentrations in patients hospitalized in ICU and likely reflects the close monitoring of renal function in this setting. For some patients (more severely ill, obese, or significant change in renal function during vancomycin therapy), predictions were less precise.

High rates of albuminuria but not of low eGFR in urban indigenous Australians: the DRUID study

Background

Indigenous Australians have an incidence of end stage kidney disease 8-10 times higher than non-Indigenous Australians. The majority of research studies concerning Indigenous Australians have been performed in rural or remote regions, whilst the majority of Indigenous Australians actually live in urban settings. We studied prevalence and factors associated with markers of kidney disease in an urban Indigenous Australian cohort, and compared results with those for the general Australian population.

Methods

860 Indigenous adult participants of the Darwin Region Urban Indigenous Diabetes (DRUID) Study were assessed for albuminuria (urine albumin-creatinine ratio≥2.5 mg/mmol males, ≥3.5 mg/mmol females) and low eGFR (estimated glomular filtration rate < 60 mls/min/1.73 m²). Associations between risk factors and kidney disease markers were explored. Comparison was made with the AusDiab cohort (n = 8,936 aged 25-64 years), representative of the general Australian adult population.

Results

A high prevalence of albuminuria (14.8%) was found in DRUID, whilst prevalence of low eGFR was 2.4%. Older age, higher HbA1c, hypertension, higher C-reactive protein and current smoking were independently associated with albuminuria on multiple regression. Low eGFR was independently associated with older age, hypertension, albuminuria and higher triglycerides. Compared to AusDiab participants, DRUID participants had a 3-fold higher adjusted risk of albuminuria but not of low eGFR.

Conclusions

Given the significant excess of ESKD observed in Indigenous versus non-Indigenous Australians, these findings could suggest either: albuminuria may be a better prognostic marker of kidney disease than low eGFR; that eGFR equations may be inaccurate in the Indigenous population; a less marked differential between Indigenous and non-Indigenous Australians for ESKD rates in urban compared to remote regions; or that differences in the pathophysiology of chronic kidney disease exist between Indigenous and non-Indigenous populations.

Gentamicin pharmacokinetics in old age and frailty

AIMS

Frailty, a syndrome of decreased physiological reserve that is prevalent in old age, impacts on clinical pharmacology. The aims of the study were to (1) determine whether frailty affects the pharmacokinetics of gentamicin and (2) assess the accuracy of different estimates of body size and renal clearance as estimates of gentamicin pharmacokinetics in older inpatients.

METHODS

This was an observational study of gentamicin pharmacokinetics in a cohort of Australian hospital inpatients aged ≥65 years, who were administered prophylactic intravenous gentamicin.

RESULTS

Of the 31 participants, 14 were frail and 17 non frail on the Reported Edmonton Frail Scale. The mean volume of distribution of gentamicin was 14.8 ± 1.4 l in frail participants and 15.3 ± 2.2 l in non frail (NS). Volume of distribution correlated best with lean bodyweight. Gentamicin clearance was significantly lower in frail participants (46.6 ± 10.7 ml min(-1)) than in non frail (58.2 ± 12.4 ml min(-1), P=0.01). The Cockcroft Gault estimate of creatinine clearance calculated using ideal bodyweight gave the best estimate of gentamicin clearance (mean error -0.15 ml min(-1), 95% CI -2.67, 2.39). The Cockcroft Gault creatinine clearance calculated using actual bodyweight and the estimated glomerular filtration rate from the modified diet in renal disease equation overestimated gentamicin clearance, with mean errors of -10.15 ml min(-1) (95%CI -13.60, -6.71) and -18.86 ml min(-1) (95% CI -22.45, -15.27), respectively. The Cockcroft Gault creatinine clearance calculated using lean bodyweight underestimated gentamicin clearance (mean error 6.54 ml min(-1), 95% CI 4.18, 8.90).

CONCLUSIONS

Frail older people have significantly lower gentamicin clearance than non frail. The best estimate of gentamicin clearance is obtained from the Cockcroft Gault creatinine clearance calculated using ideal bodyweight.

Characterizing pre-dialysis care in the era of eGFR reporting: a cohort study

Background

Chronic kidney disease (CKD) is a common disorder associated with increased morbidity and mortality. Primary care physicians (PCPs) care for the majority of pre-dialysis CKD patients; however, PCPs often do not recognize the presence of CKD based on serum creatinine levels. Prior studies suggest that PCPs and nephrologists deliver suboptimal CKD care. One strategy to improve disease awareness and treatment is estimated glomerular filtration rate (eGFR) reporting. We examined PCP and nephrologist CKD practices before and after routine eGFR reporting.

Methods

We conducted a retrospective cohort study of patients with CKD 3b-4 (eGFR < 45) seen at a university-based, outpatient primary care clinic. Using a chi-square or Fisher's exact test, we compared co-management rates, renal protective strategies, CKD documentation, and laboratory processes of care in 274 patients and 266 patients seen in a 6-month period prior to and following eGFR implementation, respectively.

Results

CKD co-management increased from 22.6% pre-eGFR to 48.5% post-eGFR (P < 0.0001). eGFR reporting did not improve angiotensin converting enzyme inhibitor or angiotensin receptor blocker use or quantitative urinary testing. However, non-steroidal anti-inflammatory drug avoidance (pre-eGFR 81.8% vs. post- eGFR 90.6%, P = 0.003) and phosphorus and parathyroid hormone testing improved (pre-eGFR vs. post-eGFR: 32.5% vs. 51.5%, P < 0.0001; 12.4% vs. 36.1%, P < 0.0001 respectively).

Conclusions

A marked increase in CKD co-management was observed following eGFR implementation. Although some improvements in processes of care were noted, this did not include angiotensin converting enzyme inhibitor or angiotensin receptor blocker use. Overall care remained suboptimal despite eGFR reporting; further strategies are needed to improve PCP and nephrologist CKD care.

Targeted urine microscopy in Anderson-Fabry disease: a cheap, sensitive and specific diagnostic technique

BACKGROUND

Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder resulting from the deficiency of trihexosylceramide α-galactosidase (α-Gal A). The diagnosis is often missed or delayed, and specific diagnostic tests (serum α-Gal A activity, genotyping or biopsy) are expensive and not widely available. We evaluated the diagnostic potential of urine microscopy in AFD.

METHODS

We studied 35 male and female AFD patients across a wide phenotypic spectrum and 21 controls with other renal diseases. Fresh urine sediment was examined under phase-contrast microscopy using polarized light for Maltese cross (MC) particles, anti-CD77 antibody to detect globotriaosylceramide (GL3, the substrate of α-Gal A), and anti-podocalyxin antibody to assess podocyte excretion.

RESULTS

Characteristic MC 2 particles and anti-CD77 binding within vacuolated urinary epithelial cells were both detected in AFD with high sensitivity and specificity (MC 2 detection sensitivity 100%, 95% confidence interval (CI) 85.4-100%, specificity 100%, CI 80.8-100%; anti-CD77-binding sensitivity 97.1%, CI 83.3-99.9, specificity 100%, CI 80.8-100%). Albuminuria (urinary albumin-to-creatinine ratio, ACR) correlated with quantitative particle excretion--in low, intermediate and high MC excretors, and median ACR was 1.6, 6.9 and 20.0 mg/μmol, respectively (analysis of variance P = 0.017). Podocyte staining was positive in ~50% of all AFD patients and was similar in those with and without clinical Fabry nephropathy (FN), whether or not treated with enzyme replacement.

CONCLUSIONS

Targeted urinary microscopy is a non-invasive, inexpensive, accessible and rapid diagnostic technique, especially applicable where serum α-Gal A activity and genotyping are not affordable or available. As the number of urinary MC 2 particles increases with rising albuminuria, the technique may also be useful in assessing FN burden.

Is estimated glomerular filtration rate superior to serum creatinine in predicting mortality on the waiting list for liver transplantation?

Serum creatinine is an important prognostic indicator in patients on the liver transplant waiting-list, being a component of the Model for End Stage Liver Disease (MELD) score. However, creatinine is influenced by age, gender and race, and in this role may disadvantage some individuals. The Modification of Diet in Renal Disease (MDRD) estimated glomerular filtration rate (eGFR) takes into account these variables and may be a superior measure of renal function. Our aim was to examine whether the MDRD 4-variable, 5-variable and 6-variable eGFRs are superior to serum creatinine in predicting 3-month waiting-list mortality in patients with end-stage liver disease. This was a retrospective single-centre study of 427 adults listed for first liver transplantation. The median listing MDRD 4-variable, 5-variable and 6-variable eGFR was 69, 71 and 73 ml/min/1.73 m(2) , respectively. The median listing serum creatinine was 89 μm. MDRD 4-variable (P = 0.002), 5-variable (P < 0.001) and 6-variable eGFR (P < 0.001), and serum creatinine (P < 0.001), were all predictors of mortality on the transplant waiting-list. Of the three MDRD equations, the 6-variable eGFR was the better prognostic indicator. The substitution of 6-variable eGFR for serum creatinine did not improve the prognostic accuracy of the MELD (P = 0.825) and UK score for Patients with End-Stage Liver Disease (P = 0.781) scores. In conclusion the MDRD eGFR is comparable, but not superior to serum creatinine, in predicting death within 3 months of listing for liver transplantation.

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.

Prognostic value of different laboratory measures of renal function for long-term mortality after contrast media-associated renal impairment

BACKGROUND

Contrast media-induced nephropathy (CIN) is associated with markedly increased morbidity and mortality. Although creatinine is at present routinely used to characterize renal function, many studies and guidelines recommend using the estimated glomerular filtration rate (eGFR) since it was found to be much more accurate.

HYPOTHESIS

To assess whether the eGFR or creatinine alone provided a better predictive value for long-term mortality after contrast media-associated renal impairment.

METHODS

From a prospective trial with 412 patients undergoing heart catheterization, creatinine and eGFR before and after 24 h, 48-72 h, and 30 d after contrast-media exposure were assessed as well as long-term mortality.

RESULTS

Univariate Cox regression models identified increases in creatinine after 48 h (hazard rate ratio [HRR] 1.754, 95% confidence interval [CI] 1.134-2.712) and 30 d (HRR 3.157, 95% CI 1.968-5.064) as well as decreases in eGFR after 30 d (HRR 0.962, 95% CI 0.939-0.986) to be significant predictors of long-term mortality. However, by multivariable Cox regression, only increases in creatinine after 48 h (HRR 1.608, 95% CI 1.002-2.581) and after 30 d (HRR 2.685, 95% CI 1.598-4.511) turned out to be significant and independent predictors of mortality. With regard to a possibly critical threshold of creatinine increase, our data confirmed the historically grown increase in creatinine of 0.5 mg/dl or more during the first 48 h as being associated with increased mortality (p = 0.016, log rank test).

CONCLUSIONS

Serum creatinine, but not eGFR, was predictive for long-term mortality, with a threshold of 0.5 mg/dl or more indicating worse prognosis.

Advances in glomerular filtration rate-estimating equations

PURPOSE OF REVIEW

Estimated glomerular filtration rate (eGFR) is now commonly reported by clinical laboratories. Here, we review the performance of current creatinine and cystatin C-based estimating equations as well as demonstration of their utility in public health and clinical practice.

RECENT FINDINGS

Lower levels of GFR are associated with multiple adverse outcomes, including acute kidney injury and medical errors. The new Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation improves performance and risk prediction compared with the Modification of Diet in Renal Disease study equation. Current cystatin C-based equations are not accurate in all populations, even in those with reduced muscle mass or chronic illness, in which cystatin C would be expected to outperform creatinine. eGFR reporting has led to a greater number of referrals to nephrologists, but the increased numbers do not appear to be excessive or burdensome. The Modification of Diet in Renal Disease study equation appears to be able to provide drug dosage adjustments similar to the Cockcroft-Gault equation.

SUMMARY

Estimated GFRs and their reporting can improve and facilitate clinical practice for chronic kidney disease. Understanding strengths and limitations facilitates their optimal use. Endogenous filtration markers, alone or in combination, which are less dependent on non-GFR determinants of the filtration markers, are necessary to lead to more accurate eGFRs.

Prevalence of chronic kidney disease in the Black Sea Region, Turkey, and investigation of the related factors with chronic kidney disease

We aimed to assess the prevalence of CKD in the Black Sea Region, Turkey, and to evaluate any relationship between age, gender, diabetes, obesity, hypertension, and CKD. This study was conducted in 70 different areas in Tokat Province in the Black Sea Region, in the northern part of Turkey. The estimated glomerular filtration rate (eGFR) was calculated from the serum creatinine using MDRD formulas. CKD-defined estimated GFR was lower than 60 mL/min/1.73 m(2). A total of 1,079 persons were included in this study (mean age 41.4+/-17 years [range: 18-95 years], 49.4% males, 50.6% living in an urban area). Of the 1,079 individuals, 5.28% were diabetic, 22.9% were obese, and 37.8% were hypertensive. CKD was found in 62 of them (5.75%). The prevalence of CKD was 5.58% in non-diabetics and 8.77% in diabetics. No significant differences were found between two groups. The prevalence of CKD was 3.77% in non-hypertensive individuals and 8.82% in hypertensive patients, and 4.46% in non-obese and 9.31% in obese. The evident significant differences were found between groups (p < 0.0001 and p = 0.004, respectively). The prevalence of CKD increased with age within our population. A salient observation was the markedly higher prevalence of CKD in females than males (p = 0.046). There was an inverse correlation between eGFR and age (r = 0.529, p < 0.0001). The overall prevalence of CKD was 5.75% in general population. The prevalence of CKD increased with age within our population. Age, gender, obesity and hypertension were found to be significant risk factors for development of CKD in our population.

Chronic kidney disease in Tasmania

AIM

Chronic kidney disease (CKD) is a progressive disease which is becoming a major public health issue due to its high rate of premature death, poor quality of life and expensive end-stage treatment (dialysis or transplantation). The burden of this chronic condition in a community setting was examined.

METHODS

Data were obtained from 369,098 Tasmanian adults (aged >or=18 years) and included 1,640,687 measurements of creatinine taken between 1995 and 2007. In 2007 alone, testing comprised 25.5% of the state's adult population. A modelled estimate of CKD prevalence was developed.

RESULTS

For those at risk of CKD (aged >50 years), 50.6%, 70.2% and 82% had a measured creatinine (and reported estimated glomerular filtration rate (eGFR)) during the last 1, 2 and 3 years respectively. However, only 9.4% of people with eGFR of less than 60 mL/min per 1.73 m(2) had albuminuria formally measured. Estimated prevalence of stage III or greater CKD (eGFR <60 mL/min per 1.73 m(2)) was at least 11.4% of women and 8.6% of men during 2007. Detection of low eGFR increased significantly over the last 13 years. There was a large geographic variation throughout Tasmania and high relative mortality with lower eGFR. There is a broad gap between the number of people with eGFR of less than 15 mL/min per 1.73 m(2) (stage V CKD) and those receiving dialysis treatment.

CONCLUSION

The number of people identified with low eGFR has increased significantly since 1995 with a large geographic variation. Despite this, testing for kidney disease (by measuring serum creatinine and albuminuria) in people at risk is still suboptimal.

Study Protocol--accurate assessment of kidney function in Indigenous Australians: aims and methods of the eGFR study

BACKGROUND

There is an overwhelming burden of cardiovascular disease, type 2 diabetes and chronic kidney disease among Indigenous Australians. In this high risk population, it is vital that we are able to measure accurately kidney function. Glomerular filtration rate is the best overall marker of kidney function. However, differences in body build and body composition between Indigenous and non-Indigenous Australians suggest that creatinine-based estimates of glomerular filtration rate derived for European populations may not be appropriate for Indigenous Australians. The burden of kidney disease is borne disproportionately by Indigenous Australians in central and northern Australia, and there is significant heterogeneity in body build and composition within and amongst these groups. This heterogeneity might differentially affect the accuracy of estimation of glomerular filtration rate between different Indigenous groups. By assessing kidney function in Indigenous Australians from Northern Queensland, Northern Territory and Western Australia, we aim to determine a validated and practical measure of glomerular filtration rate suitable for use in all Indigenous Australians.

METHODS/DESIGN

A cross-sectional study of Indigenous Australian adults (target n = 600, 50% male) across 4 sites: Top End, Northern Territory; Central Australia; Far North Queensland and Western Australia. The reference measure of glomerular filtration rate was the plasma disappearance rate of iohexol over 4 hours. We will compare the accuracy of the following glomerular filtration rate measures with the reference measure: Modification of Diet in Renal Disease 4-variable formula, Chronic Kidney Disease Epidemiology Collaboration equation, Cockcroft-Gault formula and cystatin C- derived estimates. Detailed assessment of body build and composition was performed using anthropometric measurements, skinfold thicknesses, bioelectrical impedance and a sub-study used dual-energy X-ray absorptiometry. A questionnaire was performed for socio-economic status and medical history.

DISCUSSION

We have successfully managed several operational challenges within this multi-centre complex clinical research project performed across remote North, Western and Central Australia. It seems unlikely that a single correction factor (similar to that for African-Americans) to the equation for estimated glomerular filtration rate will prove appropriate or practical for Indigenous Australians. However, it may be that a modification of the equation in Indigenous Australians would be to include a measure of fat-free mass.

Clinical presentation of renal failure in the aged: chronic renal failure

Chronic kidney disease is increasingly being recognized in elderly individuals across the world. An understanding of the methods used to estimate or to measure kidney function, the likelihood and factors associated with progressive decline in renal function, and the clinical syndromes associated with poor renal function are key topics for individuals working across many medical disciplines. This review addresses some of the important aspects of chronic kidney disease, and summarizes some of the clinical and laboratory features associated with progressive disease.

Preoperative Estimated Glomerular Filtration Rate and RIFLE-Classified Postoperative Acute Kidney Injury Predict Length of Stay Post-Coronary Bypass Surgery in an Australian Setting

We investigated the influence of preoperative estimated glomerular filtration rate and postoperative acute kidney injury on outcomes after coronary bypass surgery in a local setting, with the focus on length of stay.

A retrospective analysis of prospectively collected data for 3302 consecutive patients who underwent coronary artery bypass graft surgery (June 1997 through to January 2007) at St Vincent's Public Hospital, Melbourne, was undertaken. Preoperative estimated glomerular filtration rate was calculated and categorised using US National Kidney Foundation cut-offs for chronic kidney disease (normal function; mild, moderate and severe dysfunction). Postoperative acute kidney injury was categorised using serum creatinine RIFLE criteria (no acute kidney injury, risk, injury and failure). Postoperative intensive care and hospital length of stay was determined.

The hazard ratios for time to hospital discharge up to one month decreased (indicating a longer length of stay) as severity of preoperative renal dysfunction category increased when compared to those with normal renal function: mild hazard ratio=1.02 (95% confidence interval: 0.91 to 1.15, P=0.70), moderate 0.87 (0.76 to 1.00, P=0.047), severe 0.47 (0.35 to 0.64, P < 0.001). Hazard ratios also decreased as severity of postoperative acute kidney injury category increased, when compared to those with no acute kidney injury: risk 0.67 (0.58 to 0.77, P <0.001), injury 0.52 (0.41 to 0.65, P <0.001), failure 0.35 (0.20 to 0.60, P <0.001).

The increasing severity of preoperative renal dysfunction and postoperative acute kidney injury were associated with increased hospital length of stay. This has implications for resource use, informed consent and case selection.

Exogenous interferences with Jaffe creatinine assays: addition of sodium dodecyl sulfate to reagent eliminates bilirubin and total protein interference with Jaffe methods

BACKGROUND

The study evaluated the impact of interferences on the analytical specificity of three commercial and commonly used creatinine methods (two Jaffe and one enzymatic).

METHODS

Manufacturer creatinine methods plus modified methods were tested with the following interferences: spiking serum with bilirubin, albumin, glucose, hemoglobin and lipid, and patient sera with maximum concentrations of bilirubin, 1,090 micromol/l and protein, 117.8 g/l.

RESULTS

Hemoglobin, 7.5 g/l and lipaemic with triglyceride concentration of 6.27 mmol/l, did not interfere with all assays. Glucose >33.3 mmol/l increased creatinine recovery for Dimension method. Samples spiked with bilirubin imparted a negative bias for Dimension and Architect methods but imparted a positive bias for Vitros assay. However, using patient sera, negative bias with bilirubin was found for all methods, from which Architect method gave the highest effect (R(2)=0.861), followed by Vitros (R(2)=0.239) and Dimension (R(2)=0.163). Protein provided the positive bias for all creatinine measurements that increased with increasing concentration (R(2) ranging from 0.104 to 0.182, P<0.0001). Addition of sodium dodecyl sulfate (SDS) in alkaline-picrate reagent reduced the effect of bilirubin and protein for kinetic Jaffe method. Although adding potassium ferricyanide was well effective for eliminating negative interference of bilirubin, it was prone to interference from protein.

CONCLUSIONS

Endogenous interferences continue to plague creatinine accuracy measurement in both Jaffe and enzymatic methods, and consequentially the estimated glomerular filtration rate. The addition of SDS to the alkaline-pirate reagent was shown to be effective in reducing bilirubin and protein interferences.