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1.  Weight loss required by the severely obese to achieve clinically important differences in health-related quality of life: two-year prospective cohort study 
BMC Medicine  2014;12(1):175.
Guidelines and experts describe 5% to 10% reductions in body weight as ‘clinically important’; however, it is not clear if 5% to 10% weight reductions correspond to clinically important improvements in health-related quality of life (HRQL). Our objective was to calculate the amount of weight loss required to attain established minimal clinically important differences (MCIDs) in HRQL, measured using three validated instruments.
Data from the Alberta Population-based Prospective Evaluation of Quality of Life Outcomes and Economic Impact of Bariatric Surgery (APPLES) study, a population-based, prospective Canadian cohort including 150 wait-listed, 200 medically managed and 150 surgically treated patients were examined. Two-year changes in weight and HRQL measures (Short-Form (SF)-12 physical (PCS; MCID = 5) and mental (MCS; MCID = 5) component summary score, EQ-5D Index (MCID = 0.03) and Visual Analog Scale (VAS; MCID = 10), Impact of Weight on Quality of Life (IWQOL)-Lite total score (MCID = 12)) were calculated. Separate multivariable linear regression models were constructed within medically and surgically treated patients to determine if weight changes achieved HRQL MCIDs. Pooled analysis in all 500 patients was performed to estimate the weight reductions required to achieve the pre-defined MCID for each HRQL instrument.
Mean age was 43.7 (SD 9.6) years, 88% were women, 92% were white, and mean initial body mass index was 47.9 (SD 8.1) kg/m2. In surgically treated patients (two-year weight loss = 16%), HRQL MCIDs were reached for all instruments except the SF-12 MCS. In medically managed patients (two-year weight loss = 3%), MCIDs were attained in the EQ-index but not the other instruments. In all patients, percent weight reductions to achieve MCIDs were: 23% (95% confidence interval (CI): 17.5, 32.5) for PCS, 25% (17.5, 40.2) for MCS, 9% (6.2, 15.0) for EQ-Index, 23% (17.3, 36.1) for EQ-VAS, and 17% (14.1, 20.4) for IWQOL-Lite total score.
Weight reductions to achieve MCIDs for most HRQL instruments are markedly higher than the conventional threshold of 5% to 10%. Surgical, but not medical treatment, consistently led to clinically important improvements in HRQL over two years.
Trial registration NCT00850356.
Electronic supplementary material
The online version of this article (doi:10.1186/s12916-014-0175-5) contains supplementary material, which is available to authorized users.
PMCID: PMC4212133  PMID: 25315502
Health-related quality of life; Weight loss; Minimal clinically important difference; Obesity; Patient reported outcomes; Bariatric care
2.  A population-based study on care and clinical outcomes in remote dwellers with heavy proteinuria 
Kidney International Supplements  2013;3(2):254-258.
Patients with proteinuria are at high risk of cardiovascular and renal complications. Since this risk can be reduced by appropriate interventions, we hypothesized that remote dwellers, who are known to have lower access to health care, might have a higher risk of complications. Using a database of all adults with at least one measure of urine protein between May 2002 and March 2009, we examined the frequency of heavy proteinuria, quality of care delivery, and rates of adverse clinical outcomes across travel distance categories to the nearest nephrologist. Heavy proteinuria was defined by an albumin:creatinine ratio ⩾60 mg/mmol, protein:creatinine ratio ⩾100 mg/mmol, or protein ⩾2+ on dipstick urinalysis. Of 1,359,330 subjects in the study, 262,209 were remote dwellers. The overall prevalence of proteinuria was 2.3%, 2.9%, and 2.5% in those who live >200, 100.1–200, and 50.1–100 km, respectively, as compared to 1.5% in those who live within 50 km of the nearest nephrologist (P<0.001). Similarly, the prevalence of heavy proteinuria was increased among remote dwellers compared to urban dwellers (P=0.001 for trend). There were no differences in markers of good-quality care or the rate of adverse outcomes (all-cause mortality, heart failure, and renal outcomes) across distance categories. However, the rates of hospitalizations and stroke were significantly higher with increased distance from the nearest nephrologist (P<0.001and 0.02, respectively). In conclusion, heavy proteinuria was common in Alberta residents, especially in remote dwellers. Care seemed similar across distance categories of travel, but with higher risk of hospitalizations and stroke among remote dwellers. Further work is needed to understand the basis for the increased risk of hospitalizations and stroke.
PMCID: PMC4089650  PMID: 25018993
adverse clinical outcomes; population; proteinuria; quality of care; remote dwellers
3.  Health Care Costs in People With Diabetes and Their Association With Glycemic Control and Kidney Function 
Diabetes Care  2013;36(5):1172-1180.
To determine the association between laboratory-derived measures of glycemic control (HbA1c) and the presence of renal complications (measured by proteinuria and estimated glomerular filtration rate [eGFR]) with the 5-year costs of caring for people with diabetes.
We estimated the cumulative 5-year cost of caring for people with diabetes using a province-wide cohort of adults with diabetes as of 1 May 2004. Costs included physician visits, hospitalizations, ambulatory care (emergency room visits, day surgery, and day medicine), and drug costs for people >65 years of age. Using linked laboratory and administrative clinical and costing data, we determined the association between baseline glycemic control (HbA1c), proteinuria, and kidney function (eGFR) and 5-year costs, controlling for age, socioeconomic status, duration of diabetes, and comorbid illness.
We identified 138,662 adults with diabetes. The mean 5-year cost of diabetes in the overall cohort was $26,978 per patient, excluding drug costs. The mean 5-year cost for the subset of people >65 years of age, including drug costs, was $44,511 (Canadian dollars). Cost increased with worsening kidney function, presence of proteinuria, and suboptimal glycemic control (HbA1c >7.9%). Increasing age, Aboriginal status, socioeconomic status, duration of diabetes, and comorbid illness were also associated with increasing cost.
The cost of caring for people with diabetes is substantial and is associated with suboptimal glycemic control, abnormal kidney function, and proteinuria. Future studies should assess if improvements in the management of diabetes, assessed with laboratory-derived measurements, result in cost reductions.
PMCID: PMC3631826  PMID: 23238665
4.  A Systematic Review of Cost-Sharing Strategies Used within Publicly-Funded Drug Plans in Member Countries of the Organisation for Economic Co-Operation and Development 
PLoS ONE  2014;9(3):e90434.
Publicly-funded drug plans vary in strategies used and policies employed to reduce continually increasing pharmaceutical expenditures. We systematically reviewed the utilization of cost-sharing strategies and physician-directed prescribing regulations in publicly-funded formularies within member nations of the Organization of Economic Cooperation and Development (OECD).
Methods & Findings
Using the OECD nations as the sampling frame, a search for cost-sharing strategies and physician-directed prescribing regulations was done using published and grey literature. Collected data was verified by a system expert within the prescription drug insurance plan in each country, to ensure the accuracy of key data elements across plans.
Significant variation in the use of cost-sharing mechanisms was seen. Copayments were the most commonly used cost-containment measure, though their use and amount varied for those with certain conditions, most often chronic diseases (in 17 countries), and by socio-economic status (either income or employment status), or with age (in 15 countries). Caps and deductibles were only used by five systems. Drug cost-containment strategies targeting physicians were also identified in 24 countries, including guideline-based prescribing, prescription monitoring and incentive structures.
There was variable use of cost-containment strategies to limit pharmaceutical expenditures in publicly funded formularies within OECD countries. Further research is needed to determine the best approach to constrain costs while maintaining access to pharmaceutical drugs.
PMCID: PMC3949707  PMID: 24618721
5.  Prioritization and willingness to pay for bariatric surgery: the patient perspective 
Canadian Journal of Surgery  2014;57(1):33-39.
Access to publicly funded bariatric surgery is limited, potential candidates face lengthy waits, and no universally accepted prioritization criteria exist. We examined patients’ perspectives regarding prioritization for surgery.
We surveyed consecutively recruited patients awaiting bariatric surgery about 9 hypothetical scenarios describing patients waiting for surgery. Respondents were asked to rank the priority of these hypothetical patients on the wait list relative to their own. Scenarios examined variations in age, clinical severity, functional impairment, social dependence and socioeconomic status. Willingness to pay for faster access was assessed using a 5-point ordinal scale and analyzed using multivariable logistic regression.
The 99 respondents had mean age of 44.7 ± 9.9 years, 76% were women, and the mean body mass index was 47.3 ± SD 7.6. The mean wait for surgery was 34.4 ± 9.4 months. Respondents assigned similar priority to hypothetical patients with characteristics identical to theirs (p = 0.22) and higher priority (greater urgency) to those exhibiting greater clinical severity (p < 0.001) and functional impairment (p = 0.003). Lower priority was assigned to patients at the extremes of age (p = 0.006), on social assistance (p < 0.001) and of high socioeconomic status (p < 0.001). Most (85%) respondents disagreed with payment to expedite access, although participants earning more than $80 000/year were less likely to disagree.
Most patients waiting for bariatric surgery consider greater clinical severity and functional impairments related to obesity to be important prioritization indicators and disagreed with paying for faster access. These findings may help inform future efforts to develop acceptable prioritization strategies for publicly funded bariatric surgery.
PMCID: PMC3908993  PMID: 24461224
6.  The evaluating self-management and educational support in severely obese patients awaiting multidisciplinary bariatric care (EVOLUTION) trial: rationale and design 
In Canada, demand for multidisciplinary bariatric (obesity) care far outstrips capacity. Consequently, prolonged wait times exist and contribute to substantial health impairments.
A supportive, educational intervention (with in-person and web-based versions) designed to enhance the self-management skills of patients wait-listed for multidisciplinary bariatric medical and surgical care has been variably implemented across Alberta, Canada. However, its effectiveness has not been evaluated. Our objectives were: 1. To determine if this program improves clinical and humanistic outcomes and is cost-effective compared to a control intervention; and 2. To compare the effectiveness and cost-effectiveness of in-person group-based versus web-based care. We hypothesize that both the web-based and in-person programs will reduce body weight and improve outcomes compared to the control group. Furthermore, we hypothesize that the in-person version will be more effective but more costly than the web-based version.
This pragmatic, prospective controlled trial will enrol 660 wait-listed subjects (220 per study arm) from regional bariatric programs in Alberta and randomly assign them to: 1. an in-person, group-based intervention (9 modules delivered over 10 sessions); 2. a web-based intervention (13 modules); and 3. controls who will receive mailed literature. Subjects will have three months to review the content assigned to them (the intervention period) after which they will immediately enter the weight management clinic. Data will be collected at baseline and every 3 months for 9 months (study end), including: 1. Clinical [5% weight loss responders (primary outcome), absolute and % weight losses, changes in obesity-related comorbidities]; 2. Humanistic (health related quality of life, patient satisfaction, depression, and self-efficacy); and 3. Economic (incremental costs and utilities and cost per change in BMI assessed from the third party health care payor perspective) outcomes. Covariate-adjusted baseline-to-nine-month change-scores will be compared between groups for each outcome using linear regression for continuous outcomes and logistic regression for dichotomous ones.
Our findings will determine whether this intervention is effective and cost-effective compared to controls and if online or in-person care delivery is preferred. This information will be useful for clinicians, health-service providers and policy makers and should be generalizable to similar publically-funded bariatric care programs.
Trial registration
Trial Identifier: NCT01860131
PMCID: PMC3751526  PMID: 24059346
Bariatric care; Wait list; Severe obesity; Randomized controlled trial; Self management
7.  Prevalence and Predictors of Self-Reported Sexual Abuse in Severely Obese Patients in a Population-Based Bariatric Program 
Journal of Obesity  2013;2013:374050.
Background. Sexual abuse may be associated with poorer weight loss outcomes following bariatric treatment. Identifying predictors of abuse would enable focused screening and may increase weight management success. Methods. We analyzed data from 500 consecutively recruited obese subjects from a population-based, regional bariatric program. The prevalence of self-reported sexual abuse was ascertained using a single interview question. Health status was measured using a visual analogue scale (VAS). Multivariable logistic regression was performed to identify sexual abuse predictors. Results. The mean age was 43.7 y (SD 9.6), 441 (88.2%) were females, 458 (91.8%) were white, and the mean body mass index (BMI) was 47.9 kg/m2 (SD 8.1). The self-reported prevalence of past abuse was 21.8% (95% CI 18.4–25.4%). Abused subjects had worse health status (VAS score 53.1 (SD 21.2) versus 58.0 (SD 20.1), P = 0.03). BMI was not associated with abuse (P > 0.5). Age, sex, BMI, and covariate-adjusted independent predictors of abuse included alcohol addiction (adjusted odds ratio 15.8; 95% CI 4.0–62.8), posttraumatic stress disorder (4.9; 2.5–9.5), borderline personality (3.8; 1.0–13.8), depression (2.4; 1.3–4.3), and lower household income (3.4; 1.6–7.0). Conclusions. Abuse was common amongst obese patients managed in a population-based bariatric program; alcohol addiction, psychiatric comorbidities, and low-income status were highly associated with sexual abuse.
PMCID: PMC3705987  PMID: 23864941
9.  Bariatric Surgery: A Systematic Review of the Clinical and Economic Evidence 
Journal of General Internal Medicine  2011;26(10):1183-1194.
Use of bariatric surgery for severe obesity has increased dramatically.
To systematically review 1. the clinical efficacy and safety, 2. cost-effectiveness of bariatric surgery, and 3. the association between number of surgeries performed (surgical volume) and outcomes.
MEDLINE (from 1950), EMBASE (from 1980), CENTRAL, EconLit, EURON EED, Harvard Center for Risk Analysis, trial registries and HTA websites were searched to January 2011.
1. Randomized controlled trials (RCTs) and 2. cost-utility and cost-minimisation studies comparing a contemporary bariatric surgery (i.e., adjustable gastric banding, Roux-en-Y gastric bypass, sleeve gastrectomy) to another contemporary surgical comparator or a non-surgical treatment or 3. Any study reporting the association between surgical volume and outcome.
Outcomes included changes in weight and obesity-related comorbidity, quality of life and mortality, surgical complications, resource utilization, and incremental cost-utility.
RCT data evaluating mortality and obesity-related comorbidity endpoints were lacking. A small RCT of 16 patients reported that adjustable gastric banding reduced weight by 27% (p < 0.01) compared to diet-treated controls over 40 weeks. Six small RCTs reported comparisons of commonly used, contemporary procedures. Gastric banding reduced weight to a lower extent than gastric bypass and sleeve gastrectomy and resulted in shorter operating times, fewer serious complications, lower weight loss efficacy, and more frequent reoperations compared to gastric bypass. Sleeve gastrectomy and gastric bypass reduced weight to a similar extent. A 2-year RCT in 50 adolescents reported that gastric banding substantially reduced weight compared to lifestyle modification (35 kg vs. 3 kg; p <0.001). Based on findings of 14 observational studies, higher volume centers and surgeons had lower mortality and complication rates. Surgery resulted in long-term incremental cost–utility ratios of $ <1.000–$40,000 (2009 USD) per quality-adjusted-life-year compared with non-surgical treatment.
Contemporary bariatric surgery appears to result in sustained weight reduction with acceptable costs but rigorous, longer-term (≥5 year) data are needed and a paucity of RCT data on mortality and obesity related comorbidity is evident. Procedure-specific variations in efficacy and risks exist and require further study to clarify the specific indications for and advantages of different procedures.
PMCID: PMC3181300  PMID: 21538168
randomized controlled trials; clincical evidence; economic evidence; systematic review
10.  Characteristics of the population eligible for and receiving publicly funded bariatric surgery in Canada 
Bariatric surgery is the most effective current treatment for severe obesity. Capacity to perform surgery within Canada’s public health system is limited and potential candidates face protracted wait times. A better understanding of the gaps between demand for surgery and the capacity to provide it is required. The purpose of this study was to quantify and characterize the bariatric surgery-eligible population in Canada in comparison to surgery-ineligible subjects and surgical recipients.
Data from adult (age > 20) respondents of the 2007–09 nationally representative Canadian Health Measures Survey (CHMS) were analyzed to estimate the prevalence and characteristics of the surgery-eligible and ineligible populations. Federally mandated administrative healthcare data (2007–08) were used to characterize surgical recipients.
In 2007–09, an estimated 1.5 million obese Canadian adults met eligibility criteria for bariatric surgery. 19.2 million were surgery-ineligible (3.4 million obese and 15.8 million non-obese). Surgery-eligible Canadians had a mean BMI of 40.1 kg/m2 (95% CI 39.3 to 40.9 kg/m2) and, compared to the surgery-ineligible obese population, were more likely to be female (62 vs. 44%), 40–59 years old (55 vs. 48%), less educated (43 vs. 35%), in the lowest socioeconomic tertile (41 vs. 34%), and inactive (73 vs. 59%). Self-rated mental health and quality of life were lower and comorbidity was higher in surgery-eligible respondents compared with the ineligible populations. The annual proportion of Canadians eligible for surgery that actually underwent a publicly funded bariatric surgery between 2007–09 was 0.1%. Surgical recipients (n = 847) had a mean age of 43.6 years (SD 11.1) and 82% were female. With the exception of type 2 diabetes, obesity-related comorbidity prevalence was much lower in surgical recipients compared to those eligible for surgery.
The proportion of bariatric surgery-eligible Canadians that undergo publicly funded bariatric surgery is very low. There are notable differences in sociodemographic profiles and prevalence of comorbidities between surgery-eligible subjects and surgical recipients.
PMCID: PMC3495843  PMID: 22984790
Canada; Bariatric surgery; Health services research; Population health; Access
11.  The impact of nocturnal hemodialysis on sexual function 
BMC Nephrology  2012;13:67.
Sexual dysfunction is common in patients with end stage renal disease (ESRD) and treatment options are limited. Observational studies suggest that nocturnal hemodialysis may improve sexual function. We compared sexual activity and responses to sexual related questions in the Kidney Disease Quality of Life Short Form questionnaire among patients randomized to frequent nocturnal or thrice weekly conventional hemodialysis.
We performed a secondary analysis of data from an RCT which enrolled 51 patients comparing frequent nocturnal and conventional thrice weekly hemodialysis. Sexual activity and responses to sexual related questions were assessed at baseline and six months using relevant questions from the Kidney Disease Quality of Life Short Form questionnaire.
Overall, there was no difference in sexual activity, or the extent to which people were bothered by the impact of kidney disease on their sex life between the two groups between randomization and 6 months. However, women and patients age < 60 who were randomized to frequent nocturnal hemodialysis were less bothered by the impact of kidney disease on their sex life at 6 months, compared with patients allocated to conventional hemodialysis (p = 0.005 and p = 0.024 respectively).
Our results suggest that frequent nocturnal hemodialysis is not associated with an improvement in sexual activity in all patients but might have an effect on the burden of kidney disease on sex life in women and patients less than 60 years of age. The validity of these subgroup findings require confirmation in future RCTs.
PMCID: PMC3457870  PMID: 22834992
Nocturnal hemodialysis; Sex; Sexual function; Frequent hemodialysis
12.  Health status, quality of life, and satisfaction of patients awaiting multidisciplinary bariatric care 
Protracted, multi-year wait times exist for bariatric care in Canada. Our objective was to examine wait-listed patients’ health status and perceptions regarding the consequences of prolonged wait times using a cross-sectional study design nested within a prospective cohort.
150 consecutive consenting subjects wait-listed for multi-disciplinary bariatric assessment in a population-based medical/surgical bariatric program were surveyed. Health status was measured using a visual analogue scale (VAS). A Waiting List Impact Questionnaire (WLIQ) examined employment, physical stress, social support, frustration, quality of life, and satisfaction with care. Multivariable linear regression analysis adjusted for age, sex and BMI identified independent predictors of lower VAS scores.
136 (91%) subjects were women, mean age was 43 years (SD 9), mean BMI was 49.4 (SD 8.3) kg/m2 and average time wait-listed was 64 days (SD 76). The mean VAS score was 53/100 (SD 22). According to the WLIQ, 47% of subjects agreed/strongly agreed that waiting affected their quality of life, 65% described wait times as ‘concerning’ and 81% as ‘frustrating’. 86% reported worsening of physical symptoms over time. Nevertheless, only 31% were dissatisfied/very dissatisfied with their overall medical care. Independent predictors of lower VAS scores were higher BMI (beta coefficient 0.42; p = 0.03), unemployment (13.7; p = 0.01) and depression (10.3; p = 0.003).
Patients wait-listed for bariatric care self-reported very impaired health status and other adverse consequences, attributing these to protracted waits. These data may help benchmark the level of health impairment in this population, understand the physical and mental toll of waiting, and assist with wait list management.
Trial registration NCT00850356
PMCID: PMC3520121  PMID: 22681857
Canada; Bariatric care; Wait list; Quality-of-life; Health services research
13.  Acute dialysis risk in living kidney donors 
Nephrology Dialysis Transplantation  2012;27(8):3291-3295.
It is crucial to carefully screen donors and essential to resist compromises. If this is respected the survival, the co-morbidity, ESRD or even acute renal failure, as shown by Lam et al. in the current issue of this journal, appear to be similar to those in the general population.
Reduced kidney function confers a higher risk of acute kidney injury at the time of an inciting event, such as sepsis. Whether the same is true in those with reduced renal mass from living kidney donation is unknown.
We conducted a population-based matched cohort study of all living kidney donors in the province of Ontario, Canada who underwent donor nephrectomy from 1992 to 2009. We manually reviewed the medical records of these living kidney donors and linked this information to provincial health care databases. Non-donors were selected from the healthiest segment of the general population.
There were 2027 donors and 20 270 matched non-donors. The median age was 43 years (interquartile range 34–50) and individuals were followed for a median of 6.6 years (maximum 17.7 years). The primary outcome was acute dialysis during any hospital stay. Reasons for hospitalization included infectious diseases, cardiovascular diseases and hematological malignancies. Only one donor received acute dialysis in follow-up (6.5 events per 100 000 person-years), a rate which was statistically no different than 14 non-donors (9.4 events per 100 000 person-years).
These results are reassuring for the practice of living kidney donation. Longer follow-up of this and other donor cohorts will provide more precise estimates about this risk.
PMCID: PMC3408936  PMID: 22290988
acute kidney injury; administrative health database; dialysis; living kidney donors
14.  Cost-effectiveness of second-line antihyperglycemic therapy in patients with type 2 diabetes mellitus inadequately controlled on metformin 
Metformin is widely accepted as first-line pharmacotherapy for patients with type 2 diabetes mellitus when glycemic control cannot be achieved by lifestyle interventions alone. However, uncertainty exists regarding the optimal second-line therapy for patients whose diabetes is inadequately controlled by metformin monotherapy. Increased use of newer, more costly agents, along with the rising incidence of type 2 diabetes, carries significant budgetary implications for health care systems. We conducted this analysis to determine the relative costs, benefits and cost-effectiveness of options for second-line treatment of type 2 diabetes.
We used the United Kingdom Prospective Diabetes Study Outcomes Model to forecast diabetes-related complications, quality-adjusted life-years and costs of alternative second-line therapies available in Canada for adults with type 2 diabetes inadequately controlled by metformin. We obtained clinical data from a systematic review and mixed treatment comparison meta-analysis, and we obtained information on costs and utilities from published sources. We performed extensive sensitivity analyses to test the robustness of results to variation in inputs and assumptions.
Sulphonylureas, when added to metformin, were associated with the most favourable cost-effectiveness estimate, with an incremental cost of $12 757 per quality-adjusted life-year gained, relative to continued metformin monotherapy. Treatment with other agents, including thiazolidinediones and dipeptidyl peptidase-4 inhibitors, had unfavourable cost-effectiveness estimates compared with sulphonylureas. These results were robust to extensive sensitivity analyses.
For most patients with type 2 diabetes that is inadequately controlled with metformin monotherapy, the addition of a sulphonylurea represents the most cost-effective second-line therapy.
PMCID: PMC3216433  PMID: 21969406
15.  Cost-effectiveness of the use of low- and high-potency statins in people at low cardiovascular risk 
Although statins have been shown to reduce the risk of cardiovascular events in patients at low cardiovascular risk, their absolute benefit is small in the short term, which may adversely affect cost-effectiveness. We sought to determine the long-term cost-effectiveness (beyond the duration of clinical trials) of low- and high-potency statins in patients at low cardiovascular risk and to estimate the impact on Canada’s publicly funded health care system.
Using Markov modelling, we performed a cost-utility analysis in which we compared low-potency statins (fluvastatin, lovastatin, pravastatin and simvastatin) and high-potency statins (atorvastatin and rosuvastatin) with no statins in a simulated cohort of low-risk patients over a lifetime horizon. Model outcomes included costs (in 2010 Canadian dollars), quality-adjusted life-years (QALYs) gained and the cost per QALY gained.
Over a lifetime horizon, the cost of managing a patient at low cardiovascular risk was estimated to be about $10 100 without statins, $15 200 with low-potency statins and $16 400 with high-potency statins. The cost per QALY gained with high-potency statins (v. no statins) was $21 300; the use of low-potency statins was not considered economically attractive. These results were robust to sensitivity analyses, although their use became economically unattractive when the duration of benefit from statin use was assumed to be less than 10 years.
Use of high-potency statins in patients at low cardiovascular risk was associated with a cost per QALY gained that was economically attractive by current standards, assuming that the benefit from statin use would continue for at least 10 years. However, the overall expenditure on statins would be substantial, and the ramifications of this practice should be carefully considered by policy-makers.
PMCID: PMC3216439  PMID: 21989469
16.  Efficacy of statins for primary prevention in people at low cardiovascular risk: a meta-analysis 
Statins were initially used to improve cardiovascular outcomes in people with established coronary artery disease, but recently their use has become more common in people at low cardiovascular risk. We did a systematic review of randomized trials to assess the efficacy and harms of statins in these individuals.
We searched MEDLINE and EMBASE (to Jan. 28, 2011), registries of health technology assessments and clinical trials, and reference lists of relevant reviews. We included trials that randomly assigned participants at low cardiovascular risk to receive a statin versus a placebo or no statin. We defined low risk as an observed 10-year risk of less than 20% for cardiovascular-related death or nonfatal myocardial infarction, but we explored other definitions in sensitivity analyses.
We identified 29 eligible trials involving a total of 80 711 participants. All-cause mortality was significantly lower among patients receiving a statin than among controls (relative risk [RR] 0.90, 95% confidence interval [CI] 0.84–0.97) for trials with a 10-year risk of cardiovascular disease < 20% [primary analysis] and 0.83, 95% CI 0.73–0.94, for trials with 10-year risk < 10% [sensitivity analysis]). Patients in the statin group were also significantly less likely than controls to have nonfatal myocardial infarction (RR 0.64, 95% CI 0.49–0.84) and nonfatal stroke (RR 0.81, 95% CI 0.68–0.96). Neither metaregression nor stratified analyses suggested statistically significant differences in efficacy between high-and low-potency statins, or larger reductions in cholesterol.
Statins were found to be efficacious in preventing death and cardiovascular morbidity in people at low cardiovascular risk. Reductions in relative risk were similar to those seen in patients with a history of coronary artery disease.
PMCID: PMC3216447  PMID: 21989464
17.  Identification of factors driving differences in cost effectiveness of first-line pharmacological therapy for uncomplicated hypertension 
The Canadian Journal of Cardiology  2010;26(5):e158-e163.
Published practice guidelines and economic evaluations have come to different conclusions regarding optimal pharmacotherapy for the treatment of uncomplicated hypertension. The drivers of these disparities are not clear. Greater understanding is needed for clinicians, researchers and policy makers to determine the most effective and sustainable strategies.
To identify how cost and cost-effectiveness considerations are used to generate recommendations by major hypertension guidelines, and determine key drivers of cost-effectiveness conclusions in available economic evaluations.
A systematic search and narrative review of major hypertension guidelines and health technology assessments of first-line antihypertensive therapy were performed.
Of the eight guidelines identified, formal cost-effectiveness analysis was rarely integrated in the formulation of recommendations. When guidelines considered costs, recommendations remained incongruent. Two economic evaluations were identified (United Kingdom and Canada); however, these differed in their conclusion of the most cost-effective agent and attractiveness of calcium channel blockers. Review of these economic evaluations suggests that cost-effectiveness conclusions are strongly influenced by relative costs of drug classes; when relative differences in drug costs are lower, the impact on associated conditions such as heart failure and diabetes influences cost-effectiveness conclusions.
In the setting of finite health care resources and significant budget impact due to high population prevalence, cost effectiveness is an important consideration in the treatment of uncomplicated hypertension. Identification of key drivers of cost effectiveness will assist interpretation and conduct of current and future economic evaluations.
PMCID: PMC2886561  PMID: 20485695
Clinical practice guidelines; Cost; Cost effectiveness; Hypertension; Pharmacotherapy
18.  Nocturnal Hypoxia and Loss of Kidney Function 
PLoS ONE  2011;6(4):e19029.
Although obstructive sleep apnea (OSA) is more common in patients with kidney disease, whether nocturnal hypoxia affects kidney function is unknown.
We studied all adult subjects referred for diagnostic testing of sleep apnea between July 2005 and December 31 2007 who had serial measurement of their kidney function. Nocturnal hypoxia was defined as oxygen saturation (SaO2) below 90% for ≥12% of the nocturnal monitoring time. The primary outcome, accelerated loss of kidney function, was defined as a decline in estimated glomerular filtration rate (eGFR) ≥4 ml/min/1.73 m2 per year.
858 participants were included and followed for a mean study period of 2.1 years. Overall 374 (44%) had nocturnal hypoxia, and 49 (5.7%) had accelerated loss of kidney function. Compared to controls without hypoxia, patients with nocturnal hypoxia had a significant increase in the adjusted risk of accelerated kidney function loss (odds ratio (OR) 2.89, 95% confidence interval [CI] 1.25, 6.67).
Nocturnal hypoxia was independently associated with an increased risk of accelerated kidney function loss. Further studies are required to determine whether treatment and correction of nocturnal hypoxia reduces loss of kidney function.
PMCID: PMC3084745  PMID: 21559506
19.  The safety of combining angiotensin-converting-enzyme inhibitors with angiotensin-receptor blockers in elderly patients: a population-based longitudinal analysis 
The risks associated with using an angiotensin-converting-enzyme (ACE) inhibitor and an angiotensin-receptor blocker together are unclear. This study was designed to determine the safety of combination therapy with these two drugs in clinical practice.
We conducted a population-based longitudinal analysis using linked administrative and laboratory data for elderly patients who were new users of an ACE inhibitor, an angiotensin-receptor blocker or a combination of both medications between May 1, 2002, and Dec. 31, 2006. We compared outcomes in patients given combination therapy versus patients given monotherapy using Cox proportional hazards analyses with adjustment for baseline characteristics.
Of the 32 312 new users of either medication (mean age 76.1 years, median creatinine level 92 μmol/L), 1750 (5.4%) received combination therapy. However, 1512 (86.4%) of the patients who were given combination therapy did not have trial-established indications such as heart failure or proteinuria. Renal dysfunction was more common among patients given combination therapy (5.2 [95% confidence interval (CI) 3.4 to 7.9] events per 1000 patients per month) than among patients given monotherapy (2.4 [95% CI 2.2 to 2.7] events per 1000 patients per month) (adjusted hazard ratio [HR] 2.36, 95% CI 1.51 to 3.71). Hyperkalemia was also more common among patients given combination therapy (2.5 [95% CI 1.4 to 4.3] events per 1000 patients per month) than among patients given monotherapy (0.9 [95% CI 0.8 to 1.0] events per 1000 patients per month) (adjusted HR 2.42, 95% CI 1.36 to 4.32). Most patients took combination therapy for only a short time (median three months before at least one agent was stopped).
Combination therapy was frequently prescribed for patients without established indications and was associated with an increased risk of adverse renal outcomes when compared with monotherapy. These results mirrored data from randomized controlled trials.
PMCID: PMC3071385  PMID: 21422125
20.  Validation of a case definition to define chronic dialysis using outpatient administrative data 
Administrative health care databases offer an efficient and accessible, though as-yet unvalidated, approach to studying outcomes of patients with chronic kidney disease and end-stage renal disease (ESRD). The objective of this study is to determine the validity of outpatient physician billing derived algorithms for defining chronic dialysis compared to a reference standard ESRD registry.
A cohort of incident dialysis patients (Jan. 1 - Dec. 31, 2008) and prevalent chronic dialysis patients (Jan 1, 2008) was selected from a geographically inclusive ESRD registry and administrative database. Four administrative data definitions were considered: at least 1 outpatient claim, at least 2 outpatient claims, at least 2 outpatient claims at least 90 days apart, and continuous outpatient claims at least 90 days apart with no gap in claims greater than 21 days. Measures of agreement of the four administrative data definitions were compared to a reference standard (ESRD registry). Basic patient characteristics are compared between all 5 patient groups.
1,118,097 individuals formed the overall population and 2,227 chronic dialysis patients were included in the ESRD registry. The three definitions requiring at least 2 outpatient claims resulted in kappa statistics between 0.60-0.80 indicating "substantial" agreement. "At least 1 outpatient claim" resulted in "excellent" agreement with a kappa statistic of 0.81.
Of the four definitions, the simplest (at least 1 outpatient claim) performed comparatively to other definitions. The limitations of this work are the billing codes used are developed in Canada, however, other countries use similar billing practices and thus the codes could easily be mapped to other systems. Our reference standard ESRD registry may not capture all dialysis patients resulting in some misclassification. The registry is linked to on-going care so this is likely to be minimal. The definition utilized will vary with the research objective.
PMCID: PMC3055853  PMID: 21362182
21.  Design and implementation of the canadian kidney disease cohort study (CKDCS): A prospective observational study of incident hemodialysis patients 
BMC Nephrology  2011;12:10.
Many nephrology observational studies use renal registries, which have well known limitations. The Canadian Kidney Disease Cohort Study (CKDCS) is a large prospective observational study of patients commencing hemodialysis in five Canadian centers. This study focuses on delineating potentially reversible determinants of adverse outcomes that occur in patients receiving dialysis for end-stage renal disease (ESRD).
The CKDCS collects information on risk factors and outcomes, and stores specimens (blood, dialysate, hair and fingernails) at baseline and in long-term follow-up. Such specimens will permit measurements of biochemical markers, proteomic and genetic parameters (proteins and DNA) not measured in routine care. To avoid selection bias, all consenting incident hemodialysis patients at participating centers are enrolled, the large sample size (target of 1500 patients), large number of exposures, and high event rates will permit the exploration of multiple potential research questions.
Preliminary Results
Data on the baseline characteristics from the first 1074 subjects showed that the average age of patients was 62 (range; 50-73) years. The leading cause of ESRD was diabetic nephropathy (41.9%), and the majority of the patients were white (80.0%). Only 18.7% of the subjects received dialysis in a satellite unit, and over 80% lived within a 50 km radius of the nearest nephrologist's practice.
The prospective design, detailed clinical information, and stored biological specimens provide a wealth of information with potential to greatly enhance our understanding of risk factors for adverse outcomes in dialysis patients. The scientific value of the stored patient tissue will grow as new genetic and biochemical markers are discovered in the future.
PMCID: PMC3050805  PMID: 21324196
22.  Population based screening for chronic kidney disease: cost effectiveness study 
Objective To determine the cost effectiveness of one-off population based screening for chronic kidney disease based on estimated glomerular filtration rate.
Design Cost utility analysis of screening with estimated glomerular filtration rate alone compared with no screening (with allowance for incidental finding of cases of chronic kidney disease). Analyses were stratified by age, diabetes, and the presence or absence of proteinuria. Scenario and sensitivity analyses, including probabilistic sensitivity analysis, were performed. Costs were estimated in all adults and in subgroups defined by age, diabetes, and hypertension.
Setting Publicly funded Canadian healthcare system.
Participants Large population based laboratory cohort used to estimate mortality rates and incidence of end stage renal disease for patients with chronic kidney disease over a five year follow-up period. Patients had not previously undergone assessment of glomerular filtration rate.
Main outcome measures Lifetime costs, end stage renal disease, quality adjusted life years (QALYs) gained, and incremental cost per QALY gained.
Results Compared with no screening, population based screening for chronic kidney disease was associated with an incremental cost of $C463 (Canadian dollars in 2009; equivalent to about £275, €308, US $382) and a gain of 0.0044 QALYs per patient overall, representing a cost per QALY gained of $C104 900. In a cohort of 100 000 people, screening for chronic kidney disease would be expected to reduce the number of people who develop end stage renal disease over their lifetime from 675 to 657. In subgroups of people with and without diabetes, the cost per QALY gained was $C22 600 and $C572 000, respectively. In a cohort of 100 000 people with diabetes, screening would be expected to reduce the number of people who develop end stage renal disease over their lifetime from 1796 to 1741. In people without diabetes with and without hypertension, the cost per QALY gained was $C334 000 and $C1 411 100, respectively.
Conclusions Population based screening for chronic kidney disease with assessment of estimated glomerular filtration rate is not cost effective overall or in subgroups of people with hypertension or older people. Targeted screening of people with diabetes is associated with a cost per QALY that is similar to that accepted in other interventions funded by public healthcare systems.
PMCID: PMC2975430  PMID: 21059726
23.  The Alberta population-based prospective evaluation of the quality of life outcomes and economic impact of bariatric surgery (APPLES) study: background, design and rationale 
Extreme obesity affects nearly 8% of Canadians, and is debilitating, costly and ultimately lethal. Bariatric surgery is currently the most effective treatment available; is associated with reductions in morbidity/mortality, improvements in quality of life; and appears cost-effective. However, current demand for surgery in Canada outstrips capacity by at least 1000-fold, causing exponential increases in already protracted, multi-year wait-times. The objectives and hypotheses of this study were as follows: 1. To serially assess the clinical, economic and humanistic outcomes in patients wait-listed for bariatric care over a 2-year period. We hypothesize deterioration in these outcomes over time; 2. To determine the clinical effectiveness and changes in quality of life associated with modern bariatric procedures compared with medically treated and wait-listed controls over 2 years. We hypothesize that surgery will markedly reduce weight, decrease the need for unplanned medical care, and increase quality of life; 3. To conduct a 3-year (1 year retrospective and 2 year prospective) economic assessment of bariatric surgery compared to medical and wait-listed controls from the societal, public payor, and health-care payor perspectives. We hypothesize that lower indirect, out of pocket and productivity costs will offset increased direct health-care costs resulting in lower total costs for bariatric surgery.
Population-based prospective cohort study of 500 consecutive, consenting adults, including 150 surgically treated patients, 200 medically treated patients and 150 wait-listed patients. Subjects will be enrolled from the Edmonton Weight Wise Regional Obesity Program (Edmonton, Alberta, Canada), with prospective bi-annual follow-up for 2 years. Mixed methods data collection, linking primary data to provincial administrative databases will be employed. Major outcomes include generic, obesity-specific and preference-based quality of life assessment, patient satisfaction, patient utilities, anthropometric indices, cardiovascular risk factors, health care utilization and direct and indirect costs.
The results will identify the spectrum of potential risks associated with protracted wait times for bariatric care and will quantify the economic, humanistic and clinical impact of surgery from the Canadian perspective. Such information is urgently needed by health-service providers and policy makers to better allocate use of finite resources. Furthermore, our findings should be widely-applicable to other publically-funded jurisdictions providing similar care to the extremely obese.
Trial Registration NCT00850356
PMCID: PMC2964692  PMID: 20932316
24.  Residual renal function after partial or radical nephrectomy for renal cell carcinoma 
Renal cell carcinoma (RCC) is often detected incidentally and early. Currently, open partial nephrectomy and laparoscopic total nephrectomy form competing technologies. The former is invasive, but nephron-sparing; the other is considered less invasive but with more loss of renal mass. Traditionally, emphasis has been placed on oncologic outcomes. However, a patient with an excellent oncologic outcome may suffer from morbidity and mortality related to renal failure. Animal models with hypertension and diabetic renal disease indicate accelerated progression of pre-existing disease after nephrectomy. Patients with RCC are older and they have a high prevalence of diabetes and hypertension. The progression of renal failure may also be accelerated after a nephrectomy. Our analysis of the available literature indicates that renal outcomes in RCC patients after surgery are relatively poorly defined. A strategy to systematically evaluate the renal function of patients with RCC, with joint discussion between the nephrologist and the oncologic team, is strongly advocated.
PMCID: PMC2950769  PMID: 20944808
25.  Association between routine and standardized blood pressure measurements and left ventricular hypertrophy among patients on hemodialysis 
BMC Nephrology  2010;11:13.
Left ventricular (LV) hypertrophy is common among patients on hemodialysis. While a relationship between blood pressure (BP) and LV hypertrophy has been established, it is unclear which BP measurement method is the strongest correlate of LV hypertrophy. We sought to determine agreement between various blood pressure measurement methods, as well as identify which method was the strongest correlate of LV hypertrophy among patients on hemodialysis.
This was a post-hoc analysis of data from a randomized controlled trial. We evaluated the agreement between seven BP measurement methods: standardized measurement at baseline; single pre- and post-dialysis, as well as mean intra-dialytic measurement at baseline; and cumulative pre-, intra- and post-dialysis readings (an average of 12 monthly readings based on a single day per month). Agreement was assessed using Lin's concordance correlation coefficient (CCC) and the Bland Altman method. Association between BP measurement method and LV hypertrophy on baseline cardiac MRI was determined using receiver operating characteristic curves and area under the curve (AUC).
Agreement between BP measurement methods in the 39 patients on hemodialysis varied considerably, from a CCC of 0.35 to 0.94, with overlapping 95% confidence intervals. Pre-dialysis measurements were the weakest predictors of LV hypertrophy while standardized, post- and inter-dialytic measurements had similar and strong (AUC 0.79 to 0.80) predictive power for LV hypertrophy.
A single standardized BP has strong predictive power for LV hypertrophy and performs just as well as more resource intensive cumulative measurements, whereas pre-dialysis blood pressure measurements have the weakest predictive power for LV hypertrophy. Current guidelines, which recommend using pre-dialysis measurements, should be revisited to confirm these results.
PMCID: PMC2901323  PMID: 20576127

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