Alberta Kidney Disease Network Research Articles

Emergency Department Use Among Adults Receiving Dialysis

People with kidney failure receiving maintenance dialysis visit the emergency department (ED) 3 times per year on average, which is 3- to 8-fold more often than the general population. Little is known about the factors that contribute to potentially preventable ED use in this population. To identify the clinical and sociodemographic factors associated with potentially preventable ED use among patients receiving maintenance dialysis. This cohort study used linked administrative health data within the Alberta Kidney Disease Network to identify adults aged 18 years or older receiving maintenance dialysis (ie, hemodialysis or peritoneal dialysis) between April 1, 2010, and March 31, 2019. Patients who had been receiving dialysis for more than 90 days were followed up from cohort entry (defined as dialysis start date plus 90 days) until death, outmigration from the province, receipt of a kidney transplant, or end of study follow-up. The Andersen behavioral model of health services was used as a conceptual framework to identify variables related to health care need, predisposing factors, and enabling factors. Data were analyzed in March 2024. Rates of all-cause ED encounters and potentially preventable ED use associated with 4 kidney disease-specific ambulatory care-sensitive conditions (hyperkalemia, heart failure, volume overload, and malignant hypertension) were calculated. Multivariable negative binomial regression models were used to examine the association between clinical and sociodemographic factors and rates of potentially preventable ED use. The cohort included 4925 adults (mean [SD] age, 60.8 [15.5] years; 3071 males [62.4%]) with kidney failure receiving maintenance hemodialysis (3183 patients) or peritoneal dialysis (1742 patients) who were followed up for a mean (SD) of 2.5 (2.0) years. In all, 3877 patients had 34 029 all-cause ED encounters (3100 [95% CI, 2996-3206] encounters per 1000 person-years). Of these, 755 patients (19.5%) had 1351 potentially preventable ED encounters (114 [95% CI, 105-124] encounters per 1000 person-years). Compared with patients with a nonpreventable ED encounter, patients with a potentially preventable ED encounter were more likely to be in the lowest income quintile (38.8% vs 30.9%; P < .001); to experience heart failure (46.8% vs 39.9%; P = .001), depression (36.6% vs 32.5%; P = .03), and chronic pain (60.1% vs 54.9%; P = .01); and to have a longer duration of dialysis (3.6 vs 2.6 years; P < .001). In multivariable regression analyses, potentially preventable ED use was higher for younger adults (incidence rate ratio [IRR], 1.69 [95% CI, 1.33-2.15] for those aged 18 to 44 years) and patients with chronic pain (IRR, 1.35 [95% CI, 1.14-1.61]), greater material deprivation (IRR, 1.57 [95% CI, 1.16-2.12]), a history of hyperkalemia (IRR, 1.31 [95% CI, 1.09-1.58]), and historically high ED use (ie, ≥3 ED encounters in the prior year; IRR, 1.46 [95% CI, 1.23-1.73). In this study of adults receiving maintenance dialysis in Alberta, Canada, among those with ED use, 1 in 5 had a potentially preventable ED encounter; reasons for such encounters were associated with both psychosocial and medical factors. The findings underscore the need for strategies that address social determinants of health to avert potentially preventable ED use in this population.

Proton Pump Inhibitors Use in Kidney Transplant Recipients: A Population-Based Study.

Kidney transplant recipients are commonly prescribed proton-pump inhibitors (PPIs), but due to concern for polypharmacy, chronic use should be limited. The objective was to describe PPI use in kidney transplant recipients beyond their first year of transplant to better inform and support deprescribing initiatives. We conducted a retrospective, population-based cohort study using linked health care databases. This study was conducted in Alberta, Canada. We included all prevalent adult, kidney-only transplant recipients between April 2008 and December 2017 who received their transplant between May 2002 and December 2017. The primary outcome was ongoing or new PPI use and patterns of use, including frequency and duration of therapy, and assessment of indication for PPI use. We ascertained baseline characteristics, covariate information, and outcome data from the Alberta Kidney Disease Network (AKDN). We compared recipients with evidence of a PPI prescription in the 3 months prior to study entry to those with a histamine-2-receptor antagonist (H2Ra) fill and those with neither. We identified 1823 kidney transplant recipients, of whom 868 (48%) were on a PPI, 215 (12%) were on an H2Ra, and 740 (41%) were on neither at baseline. Over a median follow-up of 5.4 years (interquartile range [IQR] = 2.6-9.3), there were almost 45 000 unique PPI prescriptions dispensed, the majority (80%) of which were filled by initial PPI users. Recipients who were on a PPI at baseline would spend 91% (IQR = 70-98) of their graft survival time on a PPI in follow-up, and nephrologists were the main prescribers. We identified an indication for ongoing PPI use in 54% of recipients with the most common indication being concurrent antiplatelet use (26%). Our kidney transplant recipients have access to universal health care coverage which may limit generalizability. We identified common gastrointestinal indications for PPI use but did not include rare conditions due to concerns about the validity of diagnostic codes. In addition, symptoms suggestive of reflux may not be well coded as the focus of follow-up visits is more likely to focus on kidney transplant. Many kidney transplant recipients are prescribed a PPI at, or beyond, the 1-year post-transplant date and are likely to stay on a PPI in follow-up. Almost half of the recipients in our study did not have an identifiable indication for ongoing PPI use. Nephrologists frequently prescribe PPIs to kidney transplant recipients and should be involved in deprescribing initiatives to reduce polypharmacy.

Cost of Potentially Preventable Hospitalizations Among Adults With Chronic Kidney Disease: A Population-Based Cohort Study.

Background:Prior studies report high hospitalization rates among patients with chronic kidney disease (CKD) and approximately 10% to 20.9% of hospitalizations are potentially preventable.Objective:To determine the rate, proportion, and cost of potentially preventable hospitalizations and whether this varied by CKD category.Design:Retrospective cohort study using population-based data.Setting:Alberta, Canada.Patients:All adults with an outpatient serum creatinine measurement between January 1 and December 31, 2017 in the Alberta Kidney Disease Network data repository.Measurements:CKD risk categories were based on measures of proteinuria (where available), eGFR, and use of dialysis. Patients were linked to administrative data to capture frequency and cost of hospital encounters and followed until death or end of study (December 31, 2018). The outcomes of interest were the rate and cost of potentially preventable hospitalizations, as identified using the Canadian Institute for Health Information (CIHI)-defined ambulatory care sensitive condition (ACSC) algorithm and a CKD-related ACSC algorithm.Methods:Unadjusted and adjusted rates per 1000-patient years, proportions, and cost attributable to preventable hospitalizations were identified for the cohort as a whole and for patients within each CKD risk category.Results:Of the 1,110,895 adults with eGFR and proteinuria measurements, 181,422 had CKD. During a median follow-up of 1 year, there were 62,023 hospitalizations among patients with CKD resulting in a total cost of $946 million CAD; 6907 (11.1%) of these hospitalizations were for CIHI-defined ACSCs while 4323 (7.0%) were for CKD-related ACSCs. Adjusted rates of hospitalization for ACSCs increased with CKD risk category and were highest among patients treated with dialysis. Among CKD patients, the total cost of potentially preventable hospitalizations was $79 million and $58 million CAD for CIHI-defined and CKD-related ACSCs (8.4% and 6.2% of total hospitalization cost, respectively).Limitations:Based on the ACSC construct, we were unable to determine if these hospitalizations were truly preventable.Conclusions:Potentially preventable hospitalizations have a substantial cost and burden on the health care system among people with CKD. Effective strategies that reduce preventable admissions among CKD patients may lead to significant cost savings.Trial registration:Not applicable—observational study design

Association of Angiotensin-Converting Enzyme Inhibitor or Angiotensin Receptor Blocker Use With Outcomes After Acute Kidney Injury

Patients with acute kidney injury (AKI) are at an increased long-term risk of death. Effective strategies that improve long-term outcomes in patients with AKI are unknown. To evaluate whether the use of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) after hospital discharge is associated with better outcomes in patients with AKI. This retrospective cohort study used data from the Alberta Kidney Disease Network population database to evaluate 46 253 adults 18 years or older with an episode of AKI during a hospitalization between July 1, 2008, and March 31, 2015, in Alberta, Canada. All patients who survived to hospital discharge were followed up for a minimum of 2 years. Use of an ACEI or ARB within 6 months after hospital discharge. The primary outcome was mortality; secondary outcomes included hospitalization for a renal cause, end-stage renal disease (ESRD), and a composite outcome of ESRD or sustained doubling of serum creatinine concentration. An AKI was defined as a 50% increase between prehospital and peak in-hospital serum creatinine concentrations. Propensity scores were used to construct a matched-pairs cohort of patients who did and did not have a prescription for an ACEI or ARB within 6 months after hospital discharge. The study evaluated 46 253 adults (mean [SD] age, 68.6 [16.4] years; 24 436 [52.8%] male). Within 6 months of discharge, 22 193 (48.0%) of the participants were prescribed an ACEI or ARB. After adjustment for comorbidities, ACEI or ARB use before admission, demographics, baseline kidney function, other factors related to index hospitalization, and prior health care services, ACEI or ARB use was associated with lower mortality in patients with AKI after 2 years (adjusted hazard ratio, 0.85; 95% CI, 0.81-0.89). However, patients who received an ACEI or ARB had a higher risk of hospitalization for a renal cause (adjusted hazard ratio, 1.28; 95% CI, 1.12-1.46). No association was found between ACEI or ARB use and progression to ESRD. Among patients with AKI, ACEI or ARB therapy appeared to be associated with lower mortality but a higher risk of hospitalization for a renal cause. These results suggest a potential benefit of ACEI or ARB use after AKI, but cautious monitoring for renal-specific complications may be warranted.

Risk of Hospital-Acquired Complications in Patients with Chronic Kidney Disease.

Unintended injuries or complications in hospitalized patients are common, potentially preventable, and associated with adverse consequences, including greater mortality and health care costs. Patients with CKD may be at higher risk of hospital-acquired complications (HACs). Adults from a population-based cohort (Alberta Kidney Disease Network) who were hospitalized from April 1, 2003, to March 31, 2008, made up the study cohort. Kidney function was defined using outpatient eGFR and proteinuria (protein-to-creatinine ratio or dipstick) in the year before index hospitalization. Comorbid conditions were identified using validated algorithms applied to administrative data. A specific diagnostic indicator was used to identify HACs. Complications were classified into clinically homogeneous groups and subclassified as potentially preventable (p-HACs) or always preventable (a-HACs). Multivariable logistic regressions models were used to examine the association of CKD with HACs, accounting for confounders. Of 536,549 patients, 8.5% had CKD; those with CKD were older and more likely to be admitted for circulatory system diseases than those without CKD. In fully adjusted models, the odds ratio (OR) of any hospital complication in patients with CKD (reference: no CKD) was 1.19 (95% confidence interval [95% CI], 1.18 to 1.26); there was a graded relation between the risk of HACs and CKD severity, with an OR of 1.81 (95% CI, 1.51 to 2.17) in those with the most severe CKD (eGFR, 15-29 ml/min per 1.73 m(2) and proteinuria, >30 mg/mmol). Findings were similar for p-HACs (OR, 1.20 [95% CI, 1.16 to 1.24] and 1.78 [95% CI, 1.43 to 2.11], respectively). The a-HACs had similar point estimates. The presence of CKD and its severity are associated with a higher risk of HACs, including those considered preventable. Targeted strategies to reduce complications in patients with CKD admitted to the hospital should be considered.

Vitamin D Supplementation Is Associated With Stabilization of Cardiac Autonomic Tone in IgA Nephropathy

Vitamin D deficiency is a cardiovascular risk factor.1,2 Deficiency in both 25-hydroxy vitamin D, the barometer of vitamin D status, and the more biologically active 1,25-dihydroxy vitamin D is associated with increased risk of sudden cardiac death (SCD),2–4 particularly in the chronic kidney disease (CKD) population.3,4 Studies have suggested that vitamin D supplementation may alter SCD risk by influencing activity of the cardiac autonomic nervous system, although this phenomenon has not been studied in the CKD population.5 Assessment of heart rate variability, including derivations of cardiac autonomic tone (CAT), provides predictive measures of cardiovascular risk, namely through quantification of the electric output of the cardiac autonomic nervous system.6 Patients with CKD show a marked withdrawal of parasympathetic tone,7 a strong indicator of loss of cardioprotective control and a risk factor for SCD.6 Alterations in CAT are attenuated by renin–angiotensin system (RAS)–interrupting medications, such as angiotensin-converting enzyme inhibitors.8 Given that vitamin D is a negative regulator of the RAS9 and supplementation with oral vitamin D3 is associated with improvements in CAT in healthy humans,10 we sought to determine whether oral vitamin D3 supplementation was associated with a similar improvement in CAT in humans with CKD due to IgA nephropathy. This study was approved by the Conjoint Health Research Ethics Board at the University of Calgary, and all subjects provided written informed consent. Fifteen subjects (87% men, 41±4 years) with IgA nephropathy (estimated glomerular filtration rate: 101±7 mL/min per 1.73 m2; proteinuria: 1.03±0.3 g/d) were studied after an overnight fast in high-salt balance before and after 28 days of vitamin D3 supplementation (10 000 IU/d). CAT, quantified by spectral analysis of heart rate variability (low-frequency power [LF], high-frequency power [HF], and …

Potentially Preventable Hospitalization as a Complication of CKD: A Cohort Study

Ambulatory care-sensitive conditions have been described as those that (if appropriately managed in an outpatient setting) generally do not require subsequent hospitalization. Our goal was to identify clinical populations of people who are at the highest risk of ambulatory care-sensitive conditions related to chronic kidney disease (CKD). Retrospective cohort study. 2,003,054 adults (including 238,747 adults with CKD) residing in Alberta, Canada, with at least one serum creatinine measurement between 2002 and2009. Estimated glomerular filtration rate and albuminuria categories, CKD status, demographics, and clinical characteristics. Hospitalization with heart failure, hyperkalemia, volume overload, or malignant hypertension. We used the Alberta Kidney Disease Network database, which incorporates data from Alberta Health, the Northern and Southern Alberta Renal Programs, and clinical laboratories in Alberta. During a median follow-up of 4.1 years, 43,863 participants were hospitalized for heart failure; 6,274 participants, for hyperkalemia; 2,035 participants, for volume overload; and 481 participants, for malignant hypertension. All 4 conditions were more common at lower estimated glomerular filtration rates and in the presence of albuminuria. In the subset of participants with CKD, heart failure, hyperkalemia, and volume overload were associated most strongly with older age, diabetes, chronic liver disease, and prior heart failure. Malignant hypertension was associated with prior hypertension, aboriginal status, and peripheral vascular disease. Remote-dwelling participants were more likely to experience heart failure and malignant hypertension than those living closer to providers. No data for medication use or potentially important process-based outcomes for study participants. Our findings suggest that future studies seeking to determine how to prevent ambulatory care-sensitive conditions in people with CKD should target remote dwellers and those with comorbid conditions such as concomitant heart failure and liver disease.

Distribution of cardiovascular disease and retinopathy in patients with type 2 diabetes according to different classification systems for chronic kidney disease: a cross-sectional analysis of the renal insufficiency and cardiovascular events (RIACE) Italian multicenter study

BackgroundThe National Kidney Foundation’s Kidney Disease Outcomes Quality Initiative (NKF’s KDOQI) staging system for chronic kidney disease (CKD) is based primarily on estimated GFR (eGFR). This study aimed at assessing whether reclassification of subjects with type 2 diabetes using two recent classifications based on both eGFR and albuminuria, the Alberta Kidney Disease Network (AKDN) and the Kidney Disease: Improving Global Outcomes (KDIGO), provides a better definition of burden from cardiovascular disease (CVD) and diabetic retinopathy (DR) than the NKF’s KDOQI classification.MethodsThis is a cross-sectional analysis of patients with type 2 diabetes (n = 15,773) from the Renal Insufficiency And Cardiovascular Events Italian Multicenter Study, consecutively visiting 19 Diabetes Clinics throughout Italy in years 2007-2008. Exclusion criteria were dialysis or renal transplantation. CKD was defined based on eGFR, as calculated from serum creatinine by the simplified Modification of Diet in Renal Disease Study equation, and albuminuria, as measured by immunonephelometry or immunoturbidimetry. DR was assessed by dilated fundoscopy. Prevalent CVD, total and by vascular bed, was assessed from medical history by recording previous documented major acute events.ResultsThough prevalence of complications increased with increasing CKD severity with all three classifications, it differed significantly between NKF’s KDOQI stages and AKDN or KDIGO risk categories. The AKDN and KDIGO systems resulted in appropriate reclassification of uncomplicated patients in the lowest risk categories and a more graded independent association with CVD and DR than the NKF’s KDOQI classification. However, CVD, but not DR prevalence was higher in the lowest risk categories of the new classifications than in the lowest stages of the NKF’s KDOQI, due to the inclusion of subjects with reduced eGFR without albuminuria. CVD prevalence differed also among eGFR and albuminuria categories grouped into AKDN and KDIGO risk category 1 and moderate, respectively, and to a lesser extent into higher risk categories.ConclusionsThough the new systems perform better than the NKF’s KDOQI in grading complications and identifying diabetic subjects without complications, they might underestimate CVD burden in patients assigned to lower risk categories and should be tested in large prospective studies.Trial registrationClinicalTrials.gov; NCT00715481

Using linked administrative data to study periprocedural mortality in obesity and chronic kidney disease (CKD)

Both obesity and chronic kidney disease (CKD) are associated with adverse periprocedural outcomes, but it is unknown how these two common conditions interact to influence risk. We examined the feasibility of combining a new procedure-related, obesity-specific flag with administrative and laboratory data and assessed the joint association between obesity and CKD with mortality. Since 2007, Alberta physicians may claim a fee supplement for performing eligible surgical and non-surgical procedures on patients with documented BMI ≥ 35 kg/m(2). We linked this information to the Alberta Kidney Disease Network registry. Participants were classified into four mutually exclusive groups based on the presence/absence of both obesity (BMI ≥ 35 kg/m(2)) and CKD (eGFR < 60 mL/min/1.73 m(2)). Mortality was assessed at 30 days following the index procedure. Of 393 659 participants, 9% were obese. Overall, 8% had obesity only, 78% neither obesity nor CKD, 13% CKD only and 1% both obesity and CKD. Unadjusted risks of mortality at 30 days were 0.3, 0.4, 2.0 and 2.1%, respectively--but decreased to 0.1, 0.2, 0.3 and 0.3%, respectively, after adjustment for age, sex, socioeconomic status, procedure type and other comorbidities. Administrative data can be feasibly combined with disease registries to study obesity-related outcomes. Results from the linked dataset demonstrated face validity--subjects with both obesity and CKD were at increased risk of periprocedural mortality, and this was driven in part by differences in age and comorbidity.

Assessment of Serum Creatinine and Kidney Function among Incident Metformin Users

Metformin is considered the first-line antihyperglycemic therapy for type 2 diabetes, but should be used with caution in people with renal insufficiency. Our study objective was to describe the proportion of patients who have an assessment of kidney function (serum creatinine [SCr] and estimated glomerular filtration rate [eGFR]) around the time of initiation of metformin in new users. We used data from the Alberta Kidney Disease Network to identify patients with diabetes (age, ≥66 y) with a new prescription for metformin from November 1, 2002, to March 31, 2008. We assessed whether SCr measurement was completed before and after metformin initiation. The eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and categorized into CKD stages. Frequency of metformin use based on SCr measurement and CKD stage was reported using descriptive statistics. A total of 22 051 subjects were identified as new metformin users. Overall, 25.4% (n=5608) had no measurement of SCr or assessment of eGFR before metformin prescription. In addition, of patients with an eGFR measurement, 38.7% (n=8544) of individuals had an eGFR of less than 60 mL/min/1.73 m(2). One quarter of patients started on metformin did not have a SCr measurement completed beforehand. Also, metformin was used commonly among patients with diabetes and CKD, potentially putting these individuals at risk for adverse events.

Association between LDL-C and risk of myocardial infarction in CKD.

LDL cholesterol (LDL-C) is an important marker of coronary risk in the general population, but its utility in people with CKD is unclear. We studied 836,060 adults from the Alberta Kidney Disease Network with at least one measurement of fasting LDL-C, estimated GFR (eGFR), and proteinuria between 2002 and 2009. All participants were free of stage 5 CKD at cohort entry. We followed participants from first eGFR measurement to March 31, 2009; we used validated algorithms applied to administrative data to ascertain primary outcome (hospitalization for myocardial infarction) and Cox regression to calculate adjusted hazard ratios (HRs) for myocardial infarction by LDL-C categories within eGFR strata. During median follow-up of 48 months, 7762 patients were hospitalized for myocardial infarction, with incidence highest among participants with the lowest eGFR. Compared with 2.6-3.39 mmol/L (referent), the risk associated with having LDL-C above 4.9 mmol/L seemed greatest for GFR≥90 ml/min per 1.73 m(2) and least for eGFR=15-59.9 ml/min per 1.73 m(2). Specifically, the adjusted HRs (95% confidence intervals) of myocardial infarction associated with LDL-C of ≥4.9 compared with 2.6-3.39 mmol/L in participants with eGFR=15-59.9, 60-89.9, and ≥90 ml/min per 1.73 m(2) were 2.06 (1.59, 2.67), 2.30 (2.00, 2.65), and 3.01 (2.46, 3.69). In conclusion, the association between higher LDL-C and risk of myocardial infarction is weaker for people with lower baseline eGFR, despite higher absolute risk of myocardial infarction. Increased LDL-C may be less useful as a marker of coronary risk among people with CKD than the general population.

Use of administrative databases for health-care planning in CKD

Good-quality information is required to plan healthcare services for patients with chronic diseases. Such information includes measures of disease burden, current care patterns and gaps in care based on quality-of-care indicators and clinical outcomes. Administrative data have long been used as a source of information for policy decisions related to the management of chronic diseases including cardiovascular disease, diabetes and hypertension. More recently, chronic kidney disease (CKD) has been acknowledged as a significant public health issue. Administrative data, particularly when supplemented by the use of routine laboratory data, have the potential to inform the development of optimal CKD care strategies, generate hypotheses about how to slow disease progression and identify risk factors for adverse outcomes. Available data may allow case identification and assessment of rates and patterns of disease progression, evaluation of risk and complications, including current gaps in care, and an estimation of associated costs. In this article, we use the example of the Alberta Kidney Disease Network to describe how researchers and policy makers can collaborate, using administrative data sources to guide health policy for the care of CKD patients.

Review: Statins reduce mortality and cardiovascular (CV) morbidity in patients with low CV risk

Source Citation Tonelli M, Lloyd A, Clement F, et al; Alberta Kidney Disease Network. Efficacy of statins for primary prevention in people at low cardiovascular risk: a meta-analysis. CMAJ. 2011;183:E1189-1202. 21989464

High eGFR and mortality: high true GFR or a marker of frailty?

A recent report from the Alberta Kidney Disease Network demonstrates that high estimated glomerular filtration rate is associated with an increased risk of all-cause mortality in both young and elderly individuals, as well as in those with and without proteinuria. Potential explanations and implications of these findings are discussed.

Referrals for Chronic Kidney Disease

CHRONIC KIDNEY DISEASE (CKD) IS CURRENTLY considered an increasing public health problem that may be ameliorated by greater patient and physician awareness, better and earlier detection, and timely management. In the past, the increasing numbers of patients with end-stage renal disease (ESRD) who received renal replacement therapy (dialysis and transplantation) seemed to be fueled by a large and increasing population of patients with CKD, but renal replacement therapy incidence rates have reached a plateau in the United States and in many other developed countries of the world. The so-called epidemic of CKD has largely abated, at least in industrialized nations. Although this may have been due in part to early detection and better management programs that resulted in slowing the rate of progression of CKD to ESRD, the reasons for the declines in rates of ESRD treated with renal replacement therapy remain obscure. The diagnosis and classification of generic CKD has been a recent development, stemming from the description of formulaic methods for estimating glomerular filtration rate (GFR) based on serum creatinine values and by efforts to define and stage CKD largely based on such estimated GFR values. In 2002, the Kidney Disease Outcomes Quality Initiative (KDOQI) of the National Kidney Foundation defined generic CKD as an estimated GFR of less than 60 mL/min/1.73 m ( stage 3 CKD). Soon thereafter, laboratories began to report calculated estimated GFR routinely along with notes regarding the KDOQI classification of CKD. This new definition of a generic “disease” combined with widespread testing of serum creatinine concentration in outpatient laboratories led to a marked increase in referrals from primary care physicians to nephrology subspecialists for evaluation of presumed CKD whenever an estimated GFR of less than 60 mL/min/1.73 m was reported. This phenomenon is documented in the study reported in this issue of JAMA by Hemmelgarn and colleagues from the Alberta Kidney Disease Network. The authors found a substantial increase in referrals to nephrologists (almost 70%) following the introduction of routine reporting of estimated GFR in a largely urban population in Alberta, Canada, with even larger increases in referral rates among patients with estimated GFR of less than 30 mL/min/1.73 m. The increases in referral rates predominantly occurred in women, patients who were middle-aged to very old, and in those with comorbidities (such as hypertension or diabetes). This study could not examine the relationship of these referrals with outcomes or cost. In a parallel study, also recently published in JAMA, Hemmelgarn and colleagues demonstrated that lower estimated GFR is linked with a higher risk of adverse outcomes, particularly when overt proteinuria was also present. The associations of proteinuria and estimated GFR with adverse outcomes were independent of each other, a finding confirmed in other studies of a similar nature. These 2 related observations from a community-wide cohort study involving a large population (approximately 920 000 to 1 135 000 participants) seem to complement each other and suggest that CKD is common, potentially harmful, and deserving of an evaluation by a subspecialist. Neither study provides any direct evidence that such evaluations would necessarily lead to better outcomes, but this hypothesis is reasonable (and testable). To date, no prospectively designed intervention study has demonstrated a reduction in rates of ESRD in an older cohort of patients with moderately reduced estimated GFR, in the range of stage 3 CKD as defined by the KDOQI. Because older patients have a lower risk of developing ESRD than of death due to cardiovascular disease, it is possible that aggressive management might paradoxically increase the incidence of treated ESRD in this group if the benefits of intervention on fatal cardiovascular disease events were disparately greater than those on progression of kidney disease. Closer inspection of the findings of Hemmelgarn et al generates some additional considerations. First, the threshold value of an estimated GFR of less than 60 mL/min/1.73 m, used by Hemmelgarn et al to define CKD, has been challenged as not being appropriate for individuals of more advanced age, particularly women,

Overview of the Alberta Kidney Disease Network

BackgroundThe Alberta Kidney Disease Network is a collaborative nephrology research organization based on a central repository of laboratory and administrative data from the Canadian province of Alberta.DescriptionThe laboratory data within the Alberta Kidney Disease Network can be used to define patient populations, such as individuals with chronic kidney disease (using serum creatinine measurements to estimate kidney function) or anemia (using hemoglobin measurements). The administrative data within the Alberta Kidney Disease Network can also be used to define cohorts with common medical conditions such as hypertension and diabetes. Linkage of data sources permits assessment of socio-demographic information, clinical variables including comorbidity, as well as ascertainment of relevant outcomes such as health service encounters and events, the occurrence of new specified clinical outcomes and mortality.ConclusionThe unique ability to combine laboratory and administrative data for a large geographically defined population provides a rich data source not only for research purposes but for policy development and to guide the delivery of health care. This research model based on computerized laboratory data could serve as a prototype for the study of other chronic conditions.