In chronic kidney disease staging the use of the chronicity criterion affects prognosis and the rate of progression

Variations in Incidence and Prognosis of Stage 4 CKD Among Adults Identified Using Different Algorithms: A Population-Based Cohort Study

RATIONALE & OBJECTIVE

Clinical guidelines define chronic kidney disease (CKD) as abnormalities of kidney structure or function for>3 months. Assessment of the duration criterion may be implemented in different ways, potentially impacting estimates of disease incidence or prevalence in the population, individual diagnosis, and treatment decisions, especially for more severe cases. We investigated differences in incidence and prognosis of CKD stage G4 identified by 1 of 4 algorithms.

STUDY DESIGN

Population-based cohort study in Alberta, Canada.

SETTING & PARTICIPANTS

Residents>18 years old with incident CKD stage G4 (eGFR 15-29mL/min/1.73m2) diagnosed between April 1, 2015, and March 31, 2018, based on administrative and laboratory data.

EXPOSURE

Four outpatient eGFR-based algorithms, increasing in stringency, for defining cohorts with CKD G4 were evaluated: (1) a single test, (2) first eGFR<30mL/min/1.73m2 and a second eGFR 15-29mL/min/1.73m2 measured>90 days apart (2 tests), (3) ≥2 eGFR measurements of<30mL/min/1.73m2 sustained for>90 days (qualifying period) and the last eGFR in the qualifying period of 15-29mL/min/1.73m2 (relaxed sustained), and (4) ≥2 consecutive measurements of 15-29mL/min/1.73m2 for>90 days (rigorous sustained).

OUTCOME

Time to the earliest of death, eGFR improvement (a sustained increase in eGFR to≥30mL/min/1.73m2 for>90 days and>25% increase from the index eGFR), or kidney failure.

ANALYTICAL APPROACH

For each of the 4 cohorts, incidence rates and event-specific cumulative incidence functions at 1 year from cohort entry were estimated.

RESULTS

The incidence rates of CKD G4 decreased as algorithms became more stringent, from 190.7 (single test) to 79.9 (rigorous sustained) per 100,000 person-years. The 2 cohorts based on sustained reductions in eGFR were of comparable size and 1-year event-specific probabilities. The 2 cohorts based on a single test and a 2-test sequence were larger and experienced higher probabilities of eGFR improvement.

LIMITATIONS

A short follow-up period of 1 year and a predominantly White population.

CONCLUSIONS

The use of more stringent algorithms for defining CKD G4 results in substantially lower estimates of disease incidence, the identification of a group with a lower probability of eGFR improvement, and a higher risk of kidney failure. These findings can inform implementation decisions of disease definitions in clinical reporting systems and research studies.

PLAIN-LANGUAGE SUMMARY

Although guidelines recommend>3 months to define chronic kidney disease (CKD), the methods for defining specific stages, particularly G4 (eGFR 15-29mL/min/1.73m2) when referral to nephrology services is recommended, have been implemented differently across studies and surveillance programs. We studied differences in incidence and prognosis of CKD G4 cohorts identified by 4 algorithms using administrative and outpatient laboratory databases in Alberta, Canada. We found that, compared with a single-test definition, more stringent definitions resulted in a lower disease incidence and identified a group with worse short-term kidney outcomes. These findings highlight the impact of the choice of algorithm used to define CKD G4 on disease burden estimates at the population level, on individual prognosis, and on treatment/referral decisions.

Kidney function monitoring and trajectories in patients with atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) and chronic kidney disease (CKD) frequently co-exist. The frequency of kidney monitoring and range of kidney function in patients with AF in clinical practice are uncertain.

METHODS

All adult Albertans with AF between 2008 and 2017 were identified using ICD-9 and -10 codes 427.3 and I48. Kidney Disease Improving Global Outcomes (KDIGO) risk categories were defined using eGFR by the Chronic Kidney Disease Epidemiology Collaborative equation and albuminuria results within 6 months of eGFR measurement. eGFR trajectories were compared from baseline to maximum value within the following year.

RESULTS

Among 105,946 patients with AF, 16.0% were KDIGO category G1 (eGFR ≥ 90), 49.0% G2 (60-89.9), 19.8% G3a (45-59.9), 11.4% G3b (30-44.9), and G4 3.8% (15-29.9). Albuminuria was normal/mild 83.4%, moderate 11.7%, and severe 4.9%. Kidney monitoring was more common among people with lower eGFR and worse albuminuria, from approximately twice annually for G1-2/A1-2 to 8 times annually in stage G4A3. Approximately 60-80% of patients received guideline-recommended monitoring, consistent across KDIGO stages. With lower baseline eGFR, annual change in eGFR decreased while the relative proportion of patients who worsened compared to improved increased: for baseline eGFR 60-89.9, 16.7% worsened vs 6.7% improved, but for eGFR 30-44.9, 8.8% worsened but only 1.0% improved.

CONCLUSION

The frequency of kidney function monitoring in patients with AF increased with worsening KDIGO risk category and adhered to KDIGO guidelines in approximately three quarters of patients. A minority of patients had moderate to severe eGFR impairment, of whom most remained stable over 1 year.

Estimating the prevalence of definitive chronic kidney disease in the Japanese general population

BACKGROUND

Most data on chronic kidney disease (CKD) prevalence has been based on single measurements of renal function and proteinuria. The aim was to determine the prevalence of CKD diagnosed by chronic proteinuria and/or reduced eGFR in a recent year in Japan.

METHODS

In the main study, using a population-based cohort in Japan, the overall prevalence of CKD, defined as persistent positive proteinuria and/or eGFR < 60 ml/min/1.73 m², was determined. Of 2,849,557 persons, 763,104 had data for eGFR and proteinuria in both 2014 and 2015. For estimating number of CKD cases in Japanese adults, a regional cohort data with age ranging 22-87 years (N = 22,037) was further applied to the analysis.

RESULTS

Definitive CKD was present in 2.3-23.0% of men and 1.7-17.1% of women age from 40 to 74 years in the main cohort. The estimated prevalence of reduced eGFR and/or proteinuria in the baseline year alone was 15.7% in men and 13.6% in women; the prevalence of definitive CKD was 10.9% in men and 9.2% in women. The number of CKD cases based on a single-year test in Japanese adults over 20 years of age increased from 13.3 million to 14.8 million between 2005 and 2015.

CONCLUSIONS

Recent changes in prevalence of CKD seem to be mainly caused by an increase in Japan's elderly population. Although past reports may lead to overdiagnosis of CKD by a single-year test, the estimated number of definitive CKD was 10.2 million in 2015.

The prevalence of chronic kidney disease in Iceland according to KDIGO criteria and age-adapted estimated glomerular filtration rate thresholds

Most epidemiological studies on chronic kidney disease (CKD) are based solely on estimated glomerular filtration rate (eGFR). Few studies have included proteinuria, while the chronicity criterion is usually omitted. To explore this, we examined the prevalence of CKD stages 1-5 in Iceland based on multiple markers of kidney damage. All serum creatinine values, urine protein measurements and diagnostic codes for kidney diseases and comorbid conditions for people aged 18 years and older were obtained from electronic medical records of all healthcare institutions in Iceland in 2008-2016. CKD was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline using diagnoses indicative of a chronic kidney disease, proteinuria and/or an eGFR under 60 mL/min/1.73 m² for over three months. Mean annual age-standardized prevalence of CKD stages 1-5 was calculated based on the KDIGO criteria and age-adapted eGFR thresholds from 2,120,147 creatinine values for 218,437 individuals, 306,531 proteinuria measurements for 86,364 individuals and 6973 individuals carrying a kidney disease diagnosis. Median age was 63 years (range, 18-106) and 47% were male. The mean annual age standardized CKD prevalence was 5.13% for men and 6.75% for women using the KDIGO criteria but by age-adapted eGFR cut-offs, the prevalence was 3.27% for men and 4.01% for women. Thus, our nationwide study, defining CKD in Iceland with strict adherence to the KDIGO criteria, demonstrates a lower prevalence of CKD than anticipated from most previous studies.

Prevalence of chronic kidney disease in the community using data from OxRen: a UK population-based cohort study

Background

Chronic kidney disease (CKD) is a largely asymptomatic condition of diminished renal function, which may not be detected until advanced stages without screening.

Aim

To establish undiagnosed and overall CKD prevalence using a cross-sectional analysis.

Design and setting

Longitudinal cohort study in UK primary care.

Method

Participants aged ≥60 years were invited to attend CKD screening visits to determine whether they had reduced renal function (estimated glomerular filtration rate [eGFR] <60 ml/min/1.73 m² or albumin:creatinine ratio ≥3 mg/mmol). Those with existing CKD, low eGFR, evidence of albuminuria, or two positive screening tests attended a baseline assessment (CKD cohort).

Results

A total of 3207 participants were recruited and 861 attended the baseline assessment. The CKD cohort consisted of 327 people with existing CKD, 257 people with CKD diagnosed through screening (CKD prevalence of 18.2%, 95% confidence interval [CI] = 16.9 to 19.6), and 277 with borderline/transient decreased renal function. In the CKD cohort, 54.4% were female, mean standard deviation (SD) age was 74.0 (SD 6.9) years, and mean eGFR was 58.0 (SD 18.4) ml/min/1.73 m². Of the 584 with confirmed CKD, 44.0% were diagnosed through screening. Over half of the CKD cohort (51.9%, 447/861) fell into CKD stages 3–5 at their baseline assessment, giving an overall prevalence of CKD stages 3–5 of 13.9% (95% CI = 12.8 to 15.1). More people had reduced eGFR using the Modification of Diet in Renal Disease (MDRD) equation than with CKD Epidemiology Collaboration (CKD-EPI) equation in the 60–75-year age group and more had reduced eGFR using CKD-EPI in the ≥80-year age group.

Conclusion

This study found that around 44.0% of people living with CKD are undiagnosed without screening, and prevalence of CKD stages 1–5 was 18.2% in participants aged >60 years. Follow-up will provide data on annual incidence, rate of CKD progression, determinants of rapid progression, and predictors of cardiovascular events.

Impact of a single eGFR and eGFR-estimating equation on chronic kidney disease reclassification: a cohort study in primary care

Background

Chronic kidney disease (CKD) is diagnosed using the estimated glomerular filtration rate (eGFR) and the urinary albumin:creatinine ratio (ACR). The eGFR is calculated from serum creatinine levels using the Modification of Diet in Renal Disease (MDRD) or Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations.

Aim

To compare the performance of one versus two eGFR/ACR measurements, and the impact of equation choice, on CKD diagnosis and classification.

Design and setting

Cohort study in primary care in the Thames Valley region of the UK.

Method

Data were from 485 participants aged >60 years in the Oxford Renal Cohort Study with at least two eGFR tests. The proportion of study participants diagnosed and classified into different CKD stages using one and two positive tests were compared. Prevalence of CKD diagnosis and classification by CKD stage were compared when eGFR was calculated using MDRD and CKD-EPI equations.

Results

Participants included in the analysis had a mean age of 72.1 (±6.8) years and 57.0% were female. Use of a single screening test overestimated the proportion of people with CKD by around 25% no matter which equation was used, compared with the use of two tests. The mean eGFR was 1.4 ml/min/1.73 m² (95% CI = 1.1 to 1.6) higher using the CKD-EPI equation compared with the MDRD equation. More patients were diagnosed with CKD when using the MDRD equation, compared with the CKD-EPI equation, once (64% versus 63%, respectively) and twice (39% versus 38%, respectively), and 16 individuals, all of who had CKD stages 2 or 3A with MDRD, were reclassified as having a normal urinary ACR when using the CKD-EPI equation.

Conclusion

Current guidance to use two eGFR measures to diagnose CKD remains appropriate in an older primary care population to avoid overdiagnosis. A change from MDRD to CKD-EPI equation could result in one in 12 patients with a CKD diagnosis with MDRD no longer having a diagnosis of CKD.

Worldwide growing epidemic of CKD: fact or fiction?

Chronic kidney disease (CKD) is recognized as a major noncommunicable disease of growing epidemic dimension worldwide. However, recent surveys have shown a marked heterogeneity of CKD prevalence in the general population, from ∼5% to 13% across countries. Methodological issues, genetic diversity, and dietary factors may all play a role. An important, currently emerging aspect of CKD epidemiology is the variability of CKD trends over time, with some countries showing a stable or even a decreased prevalence.

Why overestimate or underestimate chronic kidney disease when correct estimation is possible?

There is no doubt that the introduction of the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines 14 years ago, and their subsequent updates, have substantially contributed to the early detection of different stages of chronic kidney disease (CKD). Several recent studies from different parts of the world mention a CKD prevalence of 8-13%. However, some editorials and reviews have begun to describe the weaknesses of a substantial number of studies. Maremar (maladies rénales chroniques au Maroc) is a recently published prevalence study of CKD, hypertension, diabetes and obesity in a randomized, representative and high response rate (85%) sample of the adult population of Morocco that strictly applied the KDIGO guidelines. When adjusted to the actual adult population of Morocco (2015), a rather low prevalence of CKD (2.9%) was found. Several reasons for this low prevalence were identified; the tagine-like population pyramid of the Maremar population was a factor, but even more important were the confirmation of proteinuria found at first screening and the proof of chronicity of decreased estimated glomerular filtration rate (eGFR), eliminating false positive results. In addition, it was found that when an arbitrary single threshold of eGFR (<60 mL/min/1.73 m2) was used to classify CKD stages 3, 4 and 5, it lead to substantial 'overdiagnosis' (false positives) in the elderly (>55 years of age), particularly in those without proteinuria, haematuria or hypertension. It also resulted in a significant 'underdiagnosis' (false negatives) in younger individuals with an eGFR >60 mL/min/1.73 m2 and below the third percentile of their age-/gender-category. The use of the third percentile eGFR level as a cut-off, based on age-gender-specific reference values of eGFR, allows the detection of these false positives and negatives. There is an urgent need for additional quality studies of the prevalence of CKD using the recent KDIGO guidelines in the correct way, to avoid overestimation of the true disease state of CKD by ≥50% with potentially dramatic consequences.

Epidemiology of chronic kidney disease: think (at least) twice!

The introduction of the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines has substantially contributed to the early detection of different stages of chronic kidney disease (CKD). Several recent studies from different parts of the world mention a CKD prevalence of between 8 and 13%. There are several reasons the CKD prevalence found in a study of a particular population is clearly overestimated. The structure of the population pyramid (young or older age) of the study sample may result in high or low CKD prevalence. The absence of using an isotope dilution mass spectrometry creatinine assay can be the source of high bias in CKD prevalence. In addition, using an arbitrary single threshold of estimated glomerular filtration rate (eGFR; <60 mL/min/1.73 m2) for classifying CKD leads to a substantial 'overdiagnosis' (false positives) in the elderly (>65 years of age), particularly in those without albuminuria (or proteinuria), haematuria or hypertension. It also results in a significant 'underdiagnosis' (false negatives) in younger individuals with an eGFR >60 mL/min/1.73 m2 and below the third percentile for their age/gender category. The use of third percentile eGFR rates as a cut-off based on age/gender-specific reference values of eGFR allows the detection of these false positives and negatives. In the present article, we focus on an important and frequently omitted criterion in epidemiological studies: chronicity. Indeed, the two most important factors introducing a high number (up to 50%) of false positives are lack of confirming proteinuria and the absence of proof of chronicity of the eGFR found at first screening. There is an urgent need for quality studies of the prevalence of CKD using representative randomized samples of the population, applying the KDIGO guidelines correctly.

Effect of Underlying Renal Disease on Nutritional and Metabolic Profile of Older Adults with Reduced Renal Function

Background

Chronic kidney disease is a common condition in the general population, particularly among older adults. Renal impairment is in turn associated with metabolic and nutritional derangements and with increased risk of cardiovascular disease.

Aim

To compare the metabolic, nutritional, and cardiovascular impact of reduced kidney function between patients with and without known renal disease.

Materials and Methods

We enrolled consecutive outpatients (age ≥65 years) with reduced renal function who were divided into two groups: Group A with history of renal disease and Group B with unknown renal disease. Metabolic and nutritional parameters, including involuntary body weight loss (BWL) in the previous 6 months, mineral metabolism, inflammatory indices, and left ventricular mass index (LVMI), were evaluated.

Results

A total of 76 patients were enrolled. Group A (n = 39, M: 24, F: 15) showed greater BWL with a significant reduction of 25-hydroxyvitamin D, transferrin, cholinesterase, albumin, and LVMI with respect to Group B (p < 0.01). Conversely, Group B (n = 37, M: 23, F: 14) showed significantly increased intact parathyroid hormone, total cholesterol, low-density lipoprotein, triglycerides, and C-reactive protein when compared to Group A (p < 0.05).

Conclusion

The positive history of renal disease may negatively impact on several metabolic and nutritional parameters related to increased cardiovascular risk among older adults.

Progression and outcomes of non-dialysis dependent chronic kidney disease patients: A single center longitudinal follow-up study

AIM

Despite increase global prevalence of End stage renal disease (ESRD) and subsequent need for renal replacement therapy (RRT), relatively little is known about disease progression and prognosis of earlier stages of CKD. Current study was conducted to examine rate of CKD progression, predictors of ESRD and death.

METHODS

A total 621 patients with estimated glomerular filtration rate (eGFR) of 15-59ml/min/1.73m² (CKD stage 3 & 4) were selected and followed up for 10 years or until ESRD or death, whichever occurred first. Subjects who did not meet inclusion criteria were excluded (n=1474).

RESULTS

Annual cumulative decline in eGFR was 3.01±0.40 ml/min/1.73m² . Overall disease progression was observed in 60% patients while 18% died. Among patients with CKD stage 3, 21% progressed to stage 4, 10% to stage 5ND (non-dialysis) and 31% to RRT while mortality was observed in 16% patients. On the other hand, 8% patients with CKD stage 4 progressed to stage 5ND, 31% to RRT and mortality was observed in 24% cases. Patients with CVD, higher systolic blood pressure, elevated phosphate levels, heavy proteinuria, microscopic hematuria and use of diuretics were more likely to develop ESRD. Advancing age, low eGFR, low systolic blood pressure, low hemoglobin and baseline diabetes were found to be significant predictors of mortality while being female reduced risk of mortality.

CONCLUSION

Our data suggest that, in this CKD cohort, patients were more likely to develop ESRD than death. Prime importance should be given to mild forms of CKD to retard and even reverse CKD progression.

The global burden of chronic kidney disease: estimates, variability and pitfalls

Chronic kidney disease (CKD) is currently defined by abnormalities of kidney structure or function assessed using a matrix of variables - including glomerular filtration rate (GFR), thresholds of albuminuria and duration of injury - and is considered by many to be a common disorder globally. However, estimates of CKD prevalence vary widely, both within and between countries. The reasons for these variations are manifold, and include true regional differences in CKD prevalence, vagaries of using estimated GFR (eGFR) for identifying CKD, issues relating to the use of set GFR thresholds to define CKD in elderly populations, and concerns regarding the use of one-off testing for assessment of eGFR or albuminuria to define the prevalence of CKD in large-scale epidemiological studies. Although CKD is common, the suggestion that its prevalence is increasing in many countries might not be correct. Here, we discuss the possible origins of differences in estimates of CKD prevalence, and present possible solutions for tackling the factors responsible for the reported variations in GFR measurements. The strategies we discuss include approaches to improve testing methodologies for more accurate assessment of GFR, to improve awareness of factors that can alter GFR readouts, and to more accurately stage CKD in certain populations, including the elderly.

Chronic kidney disease, hypertension, diabetes, and obesity in the adult population of Morocco: how to avoid "over"- and "under"-diagnosis of CKD

The prevalence of hypertension, diabetes, obesity, and chronic kidney disease (CKD) in an adult Arabic-Berber population was investigated according to 2012 KDIGO guidelines. A stratified, randomized, representative sample of 10,524 participants was obtained. Weight, height, blood pressure, proteinuria (dipstick), plasma creatinine, estimated glomerular filtration rate, and fasting glycemia were measured. Abnormal results were controlled within 2 weeks; eGFR was retested at 3, 6, and 12 months. The population adjusted prevalences were 16.7% hypertension, 23.2% obesity, 13.8% glycemia, 1.6% for eGFR under 60 ml/min/1.73 m(2) and confirmed proteinuria 1.9% and hematuria 3.4%. Adjusted prevalence of CKD was 5.1%; distribution over KDIGO stages: CKD1: 17.8%; CKD2: 17.2%; CKD3: 52.5% (3A: 40.2%; 3B: 12.3%); CKD4: 4.4%; CKD5: 7.2%. An eGFR distribution within the sex and age categories was constructed using the third percentile as threshold for decreased eGFR. A single threshold (under 60 ml/min/1.73 m(2)) eGFR classifying CKD3-5 leads to "overdiagnosis" of CKD3A in the elderly, overt "underdiagnosis" in younger individuals with eGFR over 60 ml/min/1.73 m(2), below the third percentile, and no proteinuria. By using the KDIGO guidelines in a correct way, "kidney damage" (confirmed proteinuria, hematuria) and the demonstration of chronicity of decreased eGFR <60 ml/min/1.73 m(2), combined with the third percentile as a cutoff for the normality of eGFR for age and sex, overcome false positives and negatives, substantially decrease CKD3A prevalence, and greatly increase the accuracy of identifying CKD.

Maremar, prevalence of chronic kidney disease, how to avoid over-diagnosis and under-diagnosis

Chronic kidney disease is considered as a major public health problem. Recent studies mention a prevalence rate between 8%-12%. Several editorials, comments, short reviews described the weaknesses (lack of confirmation of proteinuria, and of chronicity of decreased estimated glomerular filtration rate) of a substantial number of studies and the irrational of using a single arbitrary set point, i.e. diagnosis of chronic kidney disease whenever the estimated glomerular filtration rate is less than 60mL/min/1.73m(2). Maremar (Maladies rénales chroniques au Maroc) is a prevalence study of chronic kidney disease, hypertension, diabetes and obesity in a randomized, representative, high response rate (85%), sample of the adult population of Morocco, strictly applying the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Compared to the vast majority of the available studies, Maremar has a low prevalence of chronic kidney disease (2.9% adjusted to the actual adult population of Morocco). The population pyramid, and particularly the confirmation of proteinuria and "chronicity" of the decreased estimated glomerular filtration rate are the main reasons for this low prevalence of chronic kidney disease. The choice of arbitrary single threshold of estimated glomerular filtration rate for classifying stage 3-5 chronic kidney disease inevitably leads to "over-diagnosis" (false positives) of the disease in the elderly, particularly those without proteinuria, hematuria or hypertension, and to "under-diagnosed" (false negatives) in younger individuals with an estimated glomerular filtration rate above 60mL/min/1.73m(2) and below the 3rd percentile of their age/gender category. There is an urgent need for quality studies using in a correct way the recent KDIGO guidelines when investigating the prevalence of chronic kidney disease, in order to avoid a 50 to 100% overestimation of a disease state with potential dramatic consequences. The combination of the general population screening encompassing four different major health problems in the same screening procedure, using the correct methodologies and procedures, combined with a prevention/follow-up program results in a clinically/scientifically relevant program.

Epidemiology of CKD Regression in Patients under Nephrology Care

Chronic Kidney Disease (CKD) regression is considered as an infrequent renal outcome, limited to early stages, and associated with higher mortality. However, prevalence, prognosis and the clinical correlates of CKD regression remain undefined in the setting of nephrology care. This is a multicenter prospective study in 1418 patients with established CKD (eGFR: 60–15 ml/min/1.73m²) under nephrology care in 47 outpatient clinics in Italy from a least one year. We defined CKD regressors as a ΔGFR ≥0 ml/min/1.73 m²/year. ΔGFR was estimated as the absolute difference between eGFR measured at baseline and at follow up visit after 18–24 months, respectively. Outcomes were End Stage Renal Disease (ESRD) and overall-causes Mortality.391 patients (27.6%) were identified as regressors as they showed an eGFR increase between the baseline visit in the renal clinic and the follow up visit. In multivariate regression analyses the regressor status was not associated with CKD stage. Low proteinuria was the main factor associated with CKD regression, accounting per se for 48% of the likelihood of this outcome. Lower systolic blood pressure, higher BMI and absence of autosomal polycystic disease (PKD) were additional predictors of CKD regression. In regressors, ESRD risk was 72% lower (HR: 0.28; 95% CI 0.14–0.57; p<0.0001) while mortality risk did not differ from that in non-regressors (HR: 1.16; 95% CI 0.73–1.83; p = 0.540). Spline models showed that the reduction of ESRD risk associated with positive ΔGFR was attenuated in advanced CKD stage. CKD regression occurs in about one-fourth patients receiving renal care in nephrology units and correlates with low proteinuria, BP and the absence of PKD. This condition portends better renal prognosis, mostly in earlier CKD stages, with no excess risk for mortality.

The Practical Implications of Using Estimated GFR as the Presumed Reference Variable to Estimate Transplant Chronic Kidney Disease

We determined the proportions of matched kidney transplant isotope GFRs (iGFRs) to the estimated functions (eGFRs) calculated from Isotope Dilution Mass Spectrometry (IDMS), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), and Cockcroft-Gault (CG) equations. One thousand four hundred and three iGFR/eGFR pairs on 390 kidney transplant patients were compared considering the iGFR or eGFR as the reference or test variable. Conformity of iGFR to CG estimates demonstrated the least bias of 1.3±18.4 mL/min/1.73 m2 (compared to 1.5±19.4 and - 2.2±19.2 for IDMS and CKDI-EPI, P<0.05) and CKD-EPI estimates the highest precision of 4.1±41.8 (compared to 11.3±43.9 for IDMS and 5.7±37.3 for CG; P<0.05). IDMS eGFR cut off less than 60 and less than 30 mL/min/1.73m2 were correctly matched by iGFR in 79.4% and 49.1% of the times, while CKD-EPI was matched by iGFR in 83.5% and 52.5%. CG was matched in 78.3% and 53.6%. IGFR cut off levels of less than 60, and less than 30 mL/min/1.73m2 were predicted by IDMS in 83.8% and 64.0% of the times. CKD-EPI was correct in 77.8% and 59.0% and CG in 82.5% and 41.6%, respectively. Transplant eGFR results obtained by CKD-EPI or CG are likely to be more precise and less biased than IDMS.

Renal arterial resistive index is associated with severe histological changes and poor renal outcome during chronic kidney disease

Background

Chronic kidney disease (CKD) is a growing public health problem and end stage renal disease (ESRD) represents a large human and economic burden. It is important to identify patients at high risk of ESRD. In order to determine whether renal Doppler resistive index (RI) may discriminate those patients, we analyzed whether RI was associated with identified prognosis factors of CKD, in particular histological findings, and with renal outcome.

Methods

RI was measured in the 48 hours before renal biopsy in 58 CKD patients. Clinical and biological data were collected prospectively at inclusion. Arteriosclerosis, interstitial fibrosis and glomerulosclerosis were quantitatively assessed on renal biopsy in a blinded fashion. MDRD eGFR at 18 months was collected for 35 (60%) patients. Renal function decline was defined as a decrease in eGFR from baseline of at least 5 mL/min/ 1.73 m²/year or need for chronic renal replacement therapy. Pearson’s correlation, Mann–Whitney and Chi-square tests were used for analysis of quantitative and qualitative variables respectively. Kaplan Meier analysis was realized to determine renal survival according to RI value using the log-rank test. Multiple logistic regression was performed including variables with p < 0.20 in univariate analysis.

Results

Most patients had glomerulonephritis (82%). Median age was 46 years [21–87], eGFR 59 mL/min/ 1.73m² [5–130], percentage of interstitial fibrosis 10% [0–90], glomerulosclerosis 13% [0–96] and RI 0.63 [0.31-1.00]. RI increased with age (r = 0.435, p = 0.0063), pulse pressure (r = 0.303, p = 0.022), renal atrophy (r = −0.275, p = 0.038) and renal dysfunction (r = −0.402, p = 0.0018). Patients with arterial intima/media ratio ≥ 1 (p = 0.032), interstitial fibrosis > 20% (p = 0.014) and renal function decline (p = 0.0023) had higher RI. Patients with baseline RI ≥ 0.65 had a poorer renal outcome than those with baseline RI < 0.65 (p = 0.0005). In multiple logistic regression, RI≥0.65 was associated with accelerated renal function decline independently of baseline eGFR and proteinuria/creatininuria ratio (OR=13.04 [1.984-85.727], p = 0.0075). Sensitivity, specificity, predictive positive and predictive negative values of RI ≥ 0.65 for renal function decline at 18 months were respectively 77%, 86%, 71% and 82%.

Conclusions

Our results suggest that RI ≥ 0.65 is associated with severe interstitial fibrosis and arteriosclerosis and renal function decline. Thus, RI may contribute to identify patients at high risk of ESRD who may benefit from nephroprotective treatments.

Renal function trajectory is more important than chronic kidney disease stage for managing patients with chronic kidney disease

Management of patients with chronic kidney disease (CKD) emphasizes a current level of function as calculated from the modification of diet in renal disease glomerulofiltration rate equations (eGFR) and proteinuria for staging of CKD. Change in a patient's eGFR over time (renal function trajectory) is an additional and potentially more important consideration in deciding which patients will progress to the point where they will require renal replacement therapy (RRT). Many patients with CKD 3-5 have stable renal function for years. Proteinuria/albuminuria is a primary determinant of renal trajectory which may be slowed by medications that decrease proteinuria and/or aggressively lower blood pressure. A renal trajectory of >3 ml/min/1.73 m(2)/year may relate to a need for closer renal follow-up and increased morbidity and mortality. Additional CKD population-based studies need to examine the relationship of renal trajectory to: baseline renal function; acute kidney injury episodes; age, race, sex and primary etiologies of renal disease; blood pressure control and therapies; dietary protein intake; blood glucose control in diabetics and the competitive risk of death versus the requirement for renal replacement therapy. In the elderly CKD 4 population with significant comorbidities and slow decline in renal function, the likelihood of death prior to the need for RRT should be considered before placing AV access for dialysis. Prediction models of renal progression must account for the competitive risk of death as well as stable or improved renal function to be clinically useful.

Glomerular dysfunction and associated risk factors over 4-5 years following antiretroviral therapy initiation in Africa

BACKGROUND

The aim of this study was to investigate long-term renal function in HIV-infected adults initiating antiretroviral therapy (ART) with a CD4(+) T-cell count < 200 cells/mm³ in Africa.

METHODS

This was an observational analysis within the DART trial randomizing 3,316 adults to routine laboratory and clinical monitoring (LCM) or clinically driven monitoring (CDM). Serum creatinine was measured pre-ART (all ≤ 360 μmol/l), at weeks 4 and 12, then every 12 weeks for 4-5 years; estimated glomerular filtration rate (eGFR) was determined using the Cockcroft-Gault formula. We analysed eGFR changes, and cumulative incidences of eGFR< 30 ml/min/1.73 m² and chronic kidney disease (CKD; <60 ml/min/1.73 m² or 25% decrease if <60 ml/min/1.73 m² pre-ART; confirmed >3 months).

RESULTS

At ART initiation, median CD4(+) T-cell count was 86 cells/mm³; 1,492 (45%) participants had mild (60-< 90 ml/min/1.73 m²), 237 (7%) moderate (30-<60 ml/min/1.73 m² and 7 (0.2%) severe (15-<30 ml/min/1.73 m²) decreases in eGFR. First-line ART was zidovudine/lamivudine plus tenofovir (74%), abacavir (9%) or nevirapine (17%). By 4 years, cumulative incidence of eGFR<30 ml/min/1.73 m² was 2.8% (n=90) and CKD was 5.0% (n=162). Adjusted eGFR increases to 4 years were 1, 9 and 6 ml/min/1.73 m² with tenofovir, abacavir and nevirapine, respectively (P<0.001), and 4 and 2 ml/min/1.73 m² for LCM and CDM, respectively (P=0.005; 2 and 3 ml/min/1.73 m² to 5 years; P=0.81).

CONCLUSIONS

On all regimens and monitoring strategies, severe eGFR impairment was infrequent; differences in eGFR changes were small, suggesting that first-line ART, including tenofovir, can be given safely without routine renal function monitoring.

Renal dysfunction in patients with heart failure with preserved versus reduced ejection fraction: impact of the new Chronic Kidney Disease-Epidemiology Collaboration Group formula

BACKGROUND

Prior studies in heart failure (HF) have used the Modification of Diet in Renal Disease (MDRD) equation to calculate estimated glomerular filtration rate (eGFR). The Chronic Kidney Disease-Epidemiology Collaboration Group (CKD-EPI) equation provides a more-accurate eGFR than the MDRD when compared against the radionuclide gold standard. The prevalence and prognostic import of renal dysfunction in HF if the CKD-EPI equation is used rather than the MDRD is uncertain.

METHODS AND RESULTS

We used individual patient data from 25 prospective studies to stratify patients with HF by eGFR using the CKD-EPI and the MDRD equations and examined survival across eGFR strata. In 20 754 patients (15 962 with HF with reduced ejection fraction [HF-REF] and 4792 with HF with preserved ejection fraction [HF-PEF]; mean age, 68 years; deaths per 1000 patient-years, 151; 95% CI, 146-155), 10 589 (51%) and 11 422 (55%) had an eGFR <60 mL/min using the MDRD and CKD-EPI equations, respectively. Use of the CKD-EPI equation resulted in 3760 (18%) patients being reclassified into different eGFR risk strata; 3089 (82%) were placed in a lower eGFR category and exhibited higher all-cause mortality rates (net reclassification improvement with CKD-EPI, 3.7%; 95% CI, 1.5%-5.9%). Reduced eGFR was a stronger predictor of all-cause mortality in HF-REF than in HF-PEF.

CONCLUSIONS

Use of the CKD-EPI rather than the MDRD equation to calculate eGFR leads to higher estimates of renal dysfunction in HF and a more-accurate categorization of mortality risk. Renal function is more closely related to outcomes in HF-REF than in HF-PEF.

Repeat testing is essential when estimating chronic kidney disease prevalence and associated cardiovascular risk

BACKGROUND

Investigations into chronic kidney disease (CKD) and cardiovascular disease in the CKD population may be misleading as they are often based on a single test of kidney function.

AIM

To determine whether repeat testing at 3 months to confirm a diagnosis of CKD impacts on the estimated prevalence of CKD and the estimated 10-year general cardiovascular risk of the CKD population.

DESIGN AND METHODS

Blood and urine samples from presumed healthy volunteers were analysed for evidence of CKD on recruitment and again 3 months later. Estimated 10-year cardiovascular risk was calculated using criteria determined by the Framingham study. Preliminary study: 512 volunteers were screened for CKD. Of the initial results, 206 indicated CKD or eGFR within one standard deviation of abnormal, and 142 (69%) of these were retested. Validation study: 528 volunteers were recruited and invited to return for repeat testing. A total of 214 (40.5%) participants provided repeat samples.

RESULTS

A single test indicating CKD had a positive predictive value of 0.5 (preliminary) and 0.39 (validation) for repeat abnormalities 3 months later. Participants with CKD confirmed on repeat testing had a significant increase in estimated 10-year cardiovascular risk over the population as a whole (preliminary: 16.5 vs. 11.9%, P < 0.05; validation: 18.1 vs. 9.2%, P < 0.01). Participants with a solitary test indicating CKD had no elevation in cardiovascular risk.

CONCLUSION

Repeat testing for CKD after 3 months significantly reduces the estimated prevalence of disease and identifies a population with true CKD and a cardiovascular risk significantly in excess of the general population.

Classification of chronic kidney disease in the elderly: pitfalls and errors

The average glomerular filtration rate (GFR) is lower in the elderly than in the young and is usually a consequence of biological ageing, the rate of which varies between individuals. In some subjects, the decline is aggravated by concomitant vascular disease. The prevalence of significant kidney disease in the elderly has been overestimated - largely by rendering a diagnosis of chronic kidney disease by reference to estimates of GFR which are found in the young. A stable low GFR in the elderly, provided it is physiologically sufficient to meet homeostatic demands, is not a disease per se and seldom progresses to true kidney failure. However, it can be a risk factor for acute kidney injury drug misdosing, and possibly cardiovascular disease, so it should be noted.

Prognosis of CKD patients receiving outpatient nephrology care in Italy

BACKGROUND AND OBJECTIVES

Prognosis in nondialysis chronic kidney disease (CKD) patients under regular nephrology care is rarely investigated. Design, setting, participants, & measurements We prospectively followed from 2003 to death or June 2010 a cohort of 1248 patients with CKD stages 3 to 5 and previous nephrology care ≥1 year in 25 Italian outpatient nephrology clinics. Cumulative incidence of ESRD or death before ESRD were estimated using the competing-risk approach.

RESULTS

Estimated rates (per 100 patient-years) of ESRD and death 8.3 (95% confidence interval [CI], 7.4 to 9.2) and 5.9 (95% CI 5.2 to 6.6), respectively. Risk of ESRD and death increased progressively from stages 3 to 5. ESRD was more frequent than death in stage 4 and 5 CKD, whereas the opposite was true in stage 3 CKD. Younger age, lower body mass index, proteinuria, and high phosphate predicted ESRD, whereas older age, diabetes, previous cardiovascular disease, ESRD, proteinuria, high uric acid, and anemia predicted death (P < 0.05 for all). Among modifiable risk factors, proteinuria accounted for the greatest contribution to the model fit for either outcome.

CONCLUSIONS

In patients receiving continuity of care in Italian nephrology clinics, ESRD was a more frequent outcome than death in stage 4 and 5 CKD, but the opposite was true in stage 3. Outcomes were predicted by modifiable risk factors specific to CKD. Proteinuria used in conjunction with estimated GFR refined risk stratification. These findings provide information, specific to CKD patients under regular outpatient nephrology care, for risk stratification that complement recent observations in the general population.

Definition of chronic kidney disease and measurement of kidney function in original research papers: a review of the literature

BACKGROUND

Over the past decade, chronic kidney disease (CKD) has become an area of intensive clinical and epidemiological research. Despite the clarity provided by the Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines, there appears to be within the CKD research literature significant disagreement on how to define CKD and measure kidney function.

METHODS

The objectives of this study were to investigate the variety of methods used to define CKD and to measure kidney function in original research papers as well as to investigate whether the quality of the journal had any effect on the quality of the methodology used. This was a descriptive review and not a meta-analysis. Information was extracted from each article including publication details (including the journal's impact factor), definition of CKD, method used to estimate kidney function and quantity of serum creatinine readings used to define CKD. An electronic search of MEDLINE through OVID was completed using the search term CKD. The search was limited to articles in English published in 2009. Studies were included in the review only if they were original research articles including patients with CKD. Articles were excluded if they reported data from a paediatric population, a population solely on dialysis or if there was no full-text access through OVID. Each article was assessed for quality with respect to using KDOQI CKD definition criteria. A description of the pooled data was completed and chi-square tests were used to investigate the relation between article quality and journal quality. Analysis was carried out using SPSS (15.0) and a P-value of <0.05 was considered to indicate statistical significance.

RESULTS

The final review included 301 articles. There were a variety of methods used to define CKD in original research articles. Less than 20% (n = 59) of the articles adhered to the established international criteria for defining CKD. The majority of articles (52.1%) did not indicate the quantity of serum creatinine measurements used to define CKD. The impact factor or specialist nature of the scientific journal appears to have no bearing on whether or not published articles use the gold standard KDOQI guidelines for labelling a patient with a diagnosis of CKD.

CONCLUSIONS

This review of literature found that a variety of definitions are being used in original research articles to define CKD and measure kidney function which calls into question the validity and reliability of such research findings and associated clinical guidelines. International consensus is urgently required to improve validity and generalizability of CKD research findings.

Interaction of aging and chronic kidney disease

Our goals in this review are to describe what is known about the prevalence and clinical implications of non-dialysis-dependent chronic kidney disease in the elderly and to discuss some of the most common challenges to managing older patients with chronic kidney disease.

CKD classification based on estimated GFR over three years and subsequent cardiac and mortality outcomes: a cohort study

Background

It is unknown whether defining chronic kidney disease (CKD) based on one versus two estimated glomerular filtration rate (eGFR) assessments changes the prognostic importance of reduced eGFR in a community-based population.

Methods

Participants in the Atherosclerosis Risk in Communities Study and the Cardiovascular Health Study were classified into 4 groups based on two eGFR assessments separated by 35.3 ± 2.5 months: sustained eGFR < 60 mL/min per 1.73 m² (1 mL/sec per 1.73 m²); eGFR increase (change from below to above 60); eGFR decline (change from above to below 60); and eGFR persistently ≥60. Outcomes assessed in stratified multivariable Cox models included cardiac events and a composite of cardiac events, stroke, and mortality.

Results

There were 891 (4.9%) participants with sustained eGFR < 60, 278 (1.5%) with eGFR increase, 972 (5.4%) with eGFR decline, and 15,925 (88.2%) with sustained eGFR > 60. Participants with eGFR sustained < 60 were at highest risk of cardiac and composite events [HR = 1.38 (1.15, 1.65) and 1.58 (1.41, 1.77)], respectively, followed by eGFR decline [HR = 1.20 (1.00, 1.45) and 1.32 (1.17, 1.49)]. Individuals with eGFR increase trended toward increased cardiac risk [HR = 1.25 (0.88, 1.77)] and did not significantly differ from eGFR decline for any outcome. Results were similar when estimating GFR with the CKD-EPI equation.

Conclusion

Individuals with persistently reduced eGFR are at highest risk of cardiovascular outcomes and mortality, while individuals with an eGFR < 60 mL/min per 1.73 m² at any time are at intermediate risk. Use of even a single measurement of eGFR to classify CKD in a community population appears to have prognostic value.

Screening for kidney disease in vascular patients: SCreening for Occult REnal Disease (SCORED) experience

BACKGROUND

SCreening for Occult REnal Disease (SCORED) is a novel screening guideline recently developed to identify individuals with a high likelihood of having prevalent chronic kidney disease (CKD). This simple scoring system, developed from general US representative samples and independently validated, was shown to outperform current clinical practice guidelines. Recently, CKD screening in individuals with cardiovascular disease (CVD) has been emphasized. We therefore evaluated the SCORED model in CVD patients in order to better understand the implications of CKD screening in this population.

METHODS

Two clinical trials that enrolled patients with heart attack (N = 2481) or stroke (N = 3680) were combined to create our sample. The performance of the SCORED guideline was evaluated by standard diagnostic measures. Correlations among various risk scores and their predictive abilities for recurrent CVD were ascertained.

RESULTS

For heart attack and stroke patients, respectively, the SCORED guideline yielded sensitivity of 94 and 97%, specificity of 27 and 11%, positive predictive value of 32 and 30%, negative predictive value of 93 and 89%, with AUC of 0.75 and 0.68. SCORED was strongly correlated with other risk scores and exhibited a similar performance in the prediction of recurrent CVD.

CONCLUSIONS

The higher risk of CKD in CVD patients with high SCORED values is demonstrated. This simple education and screening tool may help promote awareness of CKD in CVD patients, in addition to general populations, and assess the CKD risk and its relationship with recurrent CVD.

Chronic kidney disease definition and classification: no need for a rush to judgment

The unified approach to chronic kidney disease (CKD) as per the Kidney Disease Outcomes Initiative (KDOQI) guideline for the definition and classification of kidney disease provided a paradigm shift in the detection, evaluation, and stratification of what was a neglected clinical problem. The guideline, based on the then-available evidence, determined the problems, limitations, and gaps in the knowledge of the proposed approach. Since then, solutions to the identified problems have been sought, resolutions are in place or are forthcoming, and longitudinal and cohort studies have been undertaken to better define the epidemiology of the disease and its prognostic determinants. The guideline also fostered considerable debate on the precision of the glomerular filtration rate equations, the implications of mislabeling cases, and the large estimates of prevalent cases of CKD. Winearls and Glassock now propose a new staging of CKD, centered on its progression to end-stage renal disease. A systematic analysis of the data accrued, since the publication of the original guideline in 2002, is necessary for the consideration of any refinement or redesign of the current staging. The Kidney Disease: Improving Global Outcomes (KDIGO) has undertaken that initiative. There is no need for a rush to judgment.