Mechanisms of the cardiorenal syndromes

The kidney and heart have essential roles in maintaining blood volume homeostasis and in the regulation of systemic blood pressure. Acute or chronic dysfunction in either the heart or kidneys can induce dysfunction in the other organ, resulting in the so-called cardiorenal syndromes, which are classified into five different types. Abrupt worsening of cardiac function predisposes an individual to acute kidney injury from renal hypoperfusion or renal congestion. Progressive, sometimes permanent, chronic kidney impairment can result from chronic renal hypoperfusion or congestion. Heart failure is common in patients with acute kidney injury. Chronic kidney disease predisposes individuals to atherosclerotic, arteriosclerotic and cardiomyopathic disease. Finally, both cardiac and renal disease can also occur secondary to systemic conditions, such as diabetes or autoimmune disease. This Review examines the mechanisms presiding over the first four types of cardiorenal syndromes. These mechanisms provide a template that accounts for the heart-kidney interactions that occur in patients whose concomitant cardiac and renal conditions result from a third cause.

Validity of random-digit-dialing in recruiting controls in a case-control study

OBJECTIVES

To evaluate whether the participating controls represented the underlying population in a colorectal cancer case-control study in a geographically isolated North American population.

METHODS

The characteristics of the study controls recruited through Random-digit-dialing (RDD) were compared with those in the corresponding target population estimates.

RESULTS

Participating controls were more likely to have higher levels of education and income and were less likely to be smokers.

CONCLUSION

Study controls recruited through RDD tend to have higher socioeconomic status, which may lead to overestimation of a number of risk factors in this study.

The unintended (and costly) effects due to the introduction of an unrestricted reimbursement policy for atypical antipsychotic medications in a Canadian public prescription drug program: 1996/97 to 2005/06

BACKGROUND

Due to the increasing costs of pharmaceuticals, drug benefit programs often implement various policies that limit availability of drugs. These policies can have unforeseen consequences.

OBJECTIVES

To examine the utilization and expenditures for antipsychotic medications in a provincial government community-based drug program over a 10-year period when atypical antipsychotics were introduced and multiple reimbursement policy changes with respect to these agents were employed.

METHODS

Retrospective analysis of the Newfoundland and Labrador Prescription Drug Program (NLPDP) claims database from 1996/97 to 2005/06. Antipsychotic medication utilization and expenditure were measured and effects of changes in reimbursement policies examined. Excess expenditure was measured by subtracting the actual from modelled expenditure under different policies.

RESULTS

Between 1996/97 and 2005/06, the number of prescriptions for antipsychotic medications increased by 75% and expenditures by more than 720% to $7.2 million (peaking at $7.9 million in 2003/04), with atypical agents making up 96% of the total. Expenditure for antipsychotic medications grew by an annual average rate of 26.3%. At the same time, the number of people enrolled in the drug program declined by an annual average rate of 1.13%. The total excess amount of money spent was $266,195 per 1,000 beneficiaries during unlimited access to atypical agents.

CONCLUSION

There has been a substantial, unintentional, increase in the prescribing of atypical antipsychotics each year in Newfoundland and Labrador over the 10 years, likely due to off-label use following the unrestricted and partial restrictive access policies for these medications. Perhaps restricted access for recognized usage should be enforced.

Autosomal recessive Bardet-Biedl syndrome: first-degree relatives have no predisposition to metabolic and renal disorders

Bardet-Biedl Syndrome (BBS) is an autosomal recessive, multisystem, genetically heterogeneous, ciliopathic condition caused by mutations in multiple genes. Here we sought to determine if inheritance of a single BBS mutation increased the risks of frequent disorders of this syndrome such as obesity, hypertension, and diabetes. Various metabolic and renal diseases in a cohort of 46 patients with BBS, prospectively followed for up to 28 years, were compared to recent assessments of these factors in 96 relatives with a heterozygote mutation (carriers) and 37 relatives without a contributing mutation (non-carriers). Ten mutations in 6 genes causing this syndrome were identified in 21 families from whom DNA was obtained. The body mass index or the incidences of hypertension, diabetes, or stage 3 chronic kidney diseases were found to be similar between carriers and non-carriers but were all significantly less than those of family members with BBS. Similarly, the median age of onset of hypertension or diagnosis of stage 3 kidney disease, or the diagnosis of diabetes by age 70 were all significantly lower in those with BBS than in gene carriers or non-carriers. While our study shows that metabolic and renal events occurred frequently and at an early age in BBS, the heterozygous inheritance of any of the 10 described BBS mutations did not predispose family members to obesity, diabetes, hypertension, or renal impairment.

Erythropoietin therapy and left ventricular mass index in CKD and ESRD patients: a meta-analysis

BACKGROUND AND OBJECTIVES

The purpose was to evaluate changes in the left ventricular mass index (LVMi) among anemic chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients treated with recombinant human erythropoietin (EPO).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A systematic review of the literature, reporting LVMi for patients before and after EPO therapy, was performed. The change in LVMi from baseline to the end of treatment was calculated and stratified by severity of anemia at baseline, target hemoglobin (Hb), and stage of kidney disease.

RESULTS

Fifteen eligible studies involving 1731 patients were identified. Cohorts with severe anemia at baseline (<10 g/dl), when given EPO using a lower target level (Hb <or= 12 g/dl or Hct <or= 36%) experienced significant reductions in LVMi (-32.7 g/m(2); 95% CI: -49.4 to -16.1, P < 0.05). However, these studies lacked control groups. Cohorts with moderate anemia at baseline showed insignificant changes in LVMi: 5.3 g/m(2) (95% CI: -0.8 to 11.3) for patients assigned to a lower target, and -6.6 g/m(2) (95% CI: -17.2 to 4.0) for patients assigned to a higher target (Hb > 12 g/dl or Hct > 36%). The effect size was similar in direction for both CKD and ESRD cohorts.

CONCLUSIONS

Aggregated results from multiple studies suggest that in severe anemia conventional Hb targets for EPO therapy are associated with a reduction in LVMi, but that in moderate anemia target Hb above 12 g/dl does not have a significant beneficial impact on LVMi compared with conventional targets.

Erythropoietin therapy, hemoglobin targets, and quality of life in healthy hemodialysis patients: a randomized trial

BACKGROUND AND OBJECTIVES

The effects of different hemoglobin targets when using erythropoiesis-stimulating agents on quality of life are somewhat controversial, and predictors of change in quality of life in endstage renal disease have not been well characterized.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Five hundred ninety-six incident hemodialysis patients without symptomatic cardiac disease were randomly assigned to hemoglobin targets of 9.5 to 11.5 g/dl or 13.5 to 14.5 g/dl for 96 weeks, using epoetin_alfa as primary therapy. Patients and attending physicians were masked to treatment assignment. Quality of life, a secondary outcome, was prospectively recorded using the Kidney Disease Quality of Life (KDQoL) questionnaire at weeks 0, 24, 36, 48, 60, 72, 84, and 96, with prespecified outcomes being fatigue and quality of social interaction.

RESULTS

The mean age and prior duration of dialysis therapy of the study population were 50.8 and 0.8 yr. Mortality was low, reflecting the relatively healthy group enrolled. Of 20 domains within the KDQoL only the prespecified domain of fatigue showed significant change over time between the two groups. Improvement in fatigue scores in the high-target group ranged from 3.2 to 7.9 over time (P = 0.007) compared with change in the low-target group. Higher body mass index and lower erythropoietin dose at baseline were independent predictors of improvement in multiple KDQoL domains.

CONCLUSIONS

In relatively healthy hemodialysis patients, normal hemoglobin targets may have beneficial effects on fatigue. Improvement in multiple domains of quality of life is associated with higher body mass index and lower erythropoietin requirements.

Prediction of Lynch syndrome in consecutive patients with colorectal cancer

BACKGROUND

Lynch syndrome is caused by inherited mutations in DNA mismatch repair genes (primarily MSH2, MLH1, MSH6, and PMS2) and is one of the most prevalent inherited cancer syndromes. Several models have been developed to predict the occurrence of Lynch syndrome in high-risk patients and families, but it is not known how these models compare with one another or how they perform for colorectal cancer patients from the general population. We used data from such patients to test the ability of four models--Leiden, MMRpredict, PREMM(1,2), and MMRpro--to distinguish between those who did and did not carry DNA mismatch repair gene mutations.

METHODS

We studied a consecutive series of 725 patients who were younger than 75 years at colorectal cancer diagnosis and whose DNA mismatch repair gene mutation status was available; 18 of the 725 patients carried such a mutation. For each model, we calculated the risk score, compared the observed number of mutations with the expected number, and determined the receiver operating characteristics. All statistical tests were two-sided.

RESULTS

Although all four models overestimated the probability of a mutation (range = 1.2- to 4.3-fold), especially in low-risk patients, they could discriminate between carriers and noncarriers of a mismatch repair mutation. The areas under the receiver operating characteristics curves from the four models ranged from 0.91 to 0.96. Carriers of mutations in the MSH6 or PMS2 genes had lower risk scores than carriers of MSH2 or MLH1 mutations. For example, the MMRpredict model gave median risk scores of 24% and 94% (P < .015) for MSH6-PMS2 and MSH2-MLH1 mutation carriers, respectively. For the Leiden, MMRpredict, and PREMM(1,2) models, correcting the risk scores for bias introduced by family size improved their power to discriminate between carriers and noncarriers. After correcting for family size, the best model was MMRpredict, which achieved a sensitivity of 94% (95% confidence interval [CI] = 73% to 99%) and a specificity of 91% (95% CI = 88% to 93%) and identified a smaller proportion of patients than the revised Bethesda criteria as those who should undergo additional molecular or immunohistochemical testing (11% vs 50%).

CONCLUSION

MMRpredict was the best-performing model for identifying colorectal cancer patients who are at high risk of carrying a DNA mismatch repair gene mutation and thus should be screened for Lynch syndrome.

Bias in clinical studies of genetic diseases

Clinical epidemiological research in genetic diseases entails the assessment of phenotypes, the burden and etiology of disease, and the efficacy of preventive measures or treatments in populations. In all areas, the main focus is to describe the relationship between exposure and outcome and determine one of the following: prevalence, incidence, cause, prognosis, or effect of treatment. The accuracy of these conclusions is determined by the validity of the study. Validity is determined by addressing potential biases and possible confounders that may be responsible for the observed association. Therefore, it is important to understand the types of bias that exist and be able to assess their impact on the magnitude and direction of the observed effect. This chapter reviews the epidemiological concepts of selection bias, information bias, and confounding and discusses ways in which these sources of bias can be minimized.

The design of randomized controlled trials

Today's clinical practice relies on the application of well-designed clinical research, the gold standard test of an intervention being the randomized controlled trial. Principles of the randomized controlled trial include emphasis on the principal research question, randomization, and blinding; definitions of outcome measures, inclusion and exclusion criteria, and comorbid and confounding factors; enrolling an adequate sample size; planning data management and analysis; preventing challenges to trial integrity, such as dropout, drop-in, and bias. The application of pretrial planning is stressed to ensure the proper application of epidemiological principles, resulting in clinical studies that are feasible and generalizable. In addition, funding strategies and trial team composition are discussed.

Hemoglobin targets and blood transfusions in hemodialysis patients without symptomatic cardiac disease receiving erythropoietin therapy

BACKGROUND AND OBJECTIVES

Optimal hemoglobin targets for chronic kidney disease patients receiving erythropoiesis-stimulating agents remain controversial. The effects of different hemoglobin targets on blood transfusion requirements have not been well characterized, despite their relevance to clinical decision-making.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Five hundred ninety-six incident hemodialysis patients without symptomatic cardiac disease were randomly assigned to hemoglobin targets of 9.5 to 11.5 g/dl or 13.5 to 14.5 g/dl for 96 wk using epoetin alfa as primary therapy and changes in left ventricular structure as the primary outcome (previously reported). Patients were masked to treatment assignment. Blood transfusion data were prospectively collected at 4-wk intervals.

RESULTS

The mean age and prior duration of dialysis therapy of the study population were 50.8 and 0.8 yr, respectively. Previously reported mortality was similar in low and high-target subjects, at 4.7 (95% confidence interval 3.0, 7.3) and 3.1 (1.8, 5.4) per hundred patient years, respectively. Transfusion rates were 0.66 (0.59, 0.74) units of blood per year in low and 0.26 (0.22, 0.32) in high-target subjects (P < 0.0001). Hemoglobin level at transfusion (7.7 [7.5, 7.9]) versus 8.1 [7.6, 8.5] g/dl) were similar with both groups. High hemoglobin target was a significant predictor of time to first transfusion independent of baseline associations (hazard ratio = 0.42; 95% confidence interval = 0.26-0.67).

CONCLUSIONS

In hemodialysis patients with comparatively low mortality risks, normal hemoglobin targets may reduce the need for transfusions.

The clinical and genetic epidemiology of neuronal ceroid lipofuscinosis in Newfoundland

The neuronal ceroid lipofuscinoses (NCLs) are the commonest neurodegenerative disorders of children. The aims of this study were to determine the incidence of NCL in Newfoundland, identify the causative genes, and analyze the relationship between phenotype and genotype. Patients with NCL diagnosed between 1960 and 2005 were ascertained through the provincial genetics and pediatric neurology clinics. Fifty-two patients from 34 families were identified. DNA was obtained from 28/34 (82%) families; 18 families had mutations in the CLN2 gene, comprising five different mutations of which two were novel. One family had a CLN3 mutation, another had a novel mutation in CLN5, and five families shared the same mutation in CLN6. One family was misdiagnosed, and in two, molecular testing was inconclusive. Disease from CLN2 mutations had an earlier presentation (p = 0.003) and seizure onset (p < 0.001) compared with CLN6 mutation. There was a slower clinical course for those with CLN5 mutation compared with CLN2 mutation. NCL in Newfoundland has a high incidence, 1 in 7353 live births, and shows extensive genetic heterogeneity. The incidence of late infantile NCL, 9.0 per 100,000 (or 1 in 11,161) live births, is the highest reported in the world.

TUMOUR PATHOLOGY PREDICTS MICROSATELLITE INSTABILITY IN A POPULATION-BASED SERIES OF COLORECTAL CANCER CASES

Background: Lynch Syndrome is an autosomal dominant trait that accounts forapproximately 3% of all cases of colorectal cancer (CRC). It is caused by mutations in DNA mismatch repair (MMR) genes, most commonly MLH1 or MSH2. These MMR defects cause high levels of microsatellite instability (MSI-H) in the tumours. MSI testing of all CRCs to identify potential Lynch Syndrome cases is not practical, so the Bethesda Guidelines, which use clinical and pathological features, were created to identify those tumours most likely to be MSI-H^1. In 2007 Jenkins et. al. created MsPath, a tool based on the pathological features described in the rarely used 3^rd Bethesda criterion, to improve prediction of MSI-H tumours among CRC cases diagnosed before age 60 years^2. Methods: We collected a population-based cohort of 716 CRC cases diagnosed before age 75 years in Newfoundland. For each of these cases we collected family history, performed MSI analysis, and scored a number of pathological features for the purpose of evaluating the accuracy of the Bethesda Criteria and MsPath at predicting MSI-H tumours. Results: Our work validates the MsPath tool in the Newfoundland population for the same age group used to create the tool. We found it identified MSI-H cases with a sensitivity of 95% and specificity of 35% in our population of CRCcases diagnosed before age 60 years (n=290). We also tested this tool on our older population of CRCcases, diagnosed at ages 60 to 74 years (n=426). We found it to be at least as predictive in this population,with a sensitivity of 95% and a specificity of 42%. We then used our entire cohort (N=716) to compare MsPath with the other Bethesda criteria.Bethesda criteria 1, 2, 4 and 5 together predicted MSI-H cases with a sensitivity of 67% and a specificity of 51%. MsPath was better at identifying these cases, with a sensitivity of 95% and a specificity of 39%. Conclusions: We conclude that MsPath can be extended to include patients diagnosed with CRC before age 75 years. As well, we have found that MsPath is a better predictive tool than the Revised Bethesda Guidelines for identifying MSI-H cases within a population-based setting of colorectal cancer. References: 1. Umar, A. et. al. J Natl Cancer Inst 2004;96:261-8 2.Jenkins, M.A. et. al. Gastroenterology 2007;133:48-56

Arrhythmogenic right ventricular cardiomyopathy type 5 is a fully penetrant, lethal arrhythmic disorder caused by a missense mutation in the TMEM43 gene

Autosomal-dominant arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) causes sudden cardiac death and is characterized by clinical and genetic heterogeneity. Fifteen unrelated ARVC families with a disease-associated haplotype on chromosome 3p (ARVD5) were ascertained from a genetically isolated population. Identification of key recombination events reduced the disease region to a 2.36 Mb interval containing 20 annotated genes. Bidirectional resequencing showed one rare variant in transmembrane protein 43 (TMEM43 1073C-->T, S358L), was carried on all recombinant ARVD5 ancestral haplotypes from affected subjects and not found in population controls. The mutation occurs in a highly conserved transmembrane domain of TMEM43 and is predicted to be deleterious. Clinical outcomes in 257 affected and 151 unaffected subjects were compared, and penetrance was determined. We concluded that ARVC at locus ARVD5 is a lethal, fully penetrant, sex-influenced morbid disorder. Median life expectancy was 41 years in affected males compared to 71 years in affected females (relative risk 6.8, 95% CI 1.3-10.9). Heart failure was a late manifestation in survivors. Although little is known about the function of the TMEM43 gene, it contains a response element for PPAR gamma (an adipogenic transcription factor), which may explain the fibrofatty replacement of the myocardium, a characteristic pathological finding in ARVC.

MSH2 118T>C and MSH6 159C>T promoter polymorphisms and the risk of colorectal cancer

The most important indicator of colorectal cancer (CRC) risk is the presence of family history of the disease. Inherited genetic changes, such as single nucleotide polymorphisms, in key candidate genes may contribute to CRC risk. We investigated whether promoter polymorphisms in DNA mismatch repair (MMR) genes MSH2 and MSH6 are associated with the risk of CRC. We genotyped 929 CRC patients and 1098 control subjects from Ontario, and 467 patients and 344 controls from Newfoundland and Labrador, for two promoter polymorphisms in the MMR genes MSH2 and MSH6 using the fluorogenic 5' nuclease assay. We used unconditional logistic regression to evaluate the association between each polymorphism and CRC after adjusting for age and sex. The associations between polymorphisms and tumor clinicopathological features were evaluated with a Pearson's chi-squared test or Fisher's exact test. All statistical tests were two sided. We observed strong associations between the MSH2 -118T>C polymorphism and family history of CRC based on the Amsterdam criteria I (P = 0.005) and Amsterdam criteria I and II (P = 0.036) among cases from Ontario. This association was especially evident among female CRC patients in Ontario (for Amsterdam criteria I, and I and II combined, P = 0.003 and P = 0.0001, respectively). The MSH2 -118T>C polymorphism was associated with strong family history of CRC in Ontario patients.

Very high incidence of familial colorectal cancer in Newfoundland: a comparison with Ontario and 13 other population-based studies

Newfoundland has the highest rate of colorectal cancer (CRC) of any Canadian province. In order to investigate the factors, especially genetic components, responsible for CRC we established the Newfoundland Colorectal Cancer Registry. In a 5-year period we examined every case of CRC diagnosed under the age of 75 years and obtained consent from 730 cases. Careful analysis of family history was used to assign a familial cancer risk, based on established criteria. We observed that 3.7% of CRC cases came from families meeting the Amsterdam II criteria and a further 0.9% of cases involved familial adenomatous polyposis (FAP). An additional 43% of cases met one or more of the revised Bethesda criteria and 31% of all cases had a first-degree relative affected with CRC. We compared the Newfoundland data with data from the province of Ontario, where the same recruitment and risk-assessment criteria were used. In all categories, the indicators of familial risk were significantly higher in Newfoundland. These data were also compared to results published from 13 other population-based studies worldwide. In every category the proportion of Newfoundland cases meeting the criteria was higher than in any other population. The mean differences were: 3.5-fold greater for FAP, 2.8-fold higher for Amsterdam criteria, 2.0-fold higher for Bethesda criteria and 1.9-fold higher for the number of affected first-degree relatives. We conclude that the high incidence of CRC in Newfoundland may be attributable to genetic, or at least familial, factors. In the high-risk families we provide evidence for the involvement of founder mutations in the APC and MSH2 genes.

Predictors of registered nurses' organizational commitment and intent to stay

BACKGROUND

Health care reform has significantly altered employment relations. Research findings suggest that the presence or absence of supportive work environments helps explain the differences observed in employee attitudes and turnover intentions.

PURPOSES

The purposes of this study were to examine frontline registered nurses' (RNs') perceptions of organizational culture and attitudes and behaviors and test a model linking culture to outcome (organizational commitment and intent to stay).

METHODOLOGY

A non-experimental predictive survey design was used to test the model in a sample (N = 343) of acute care RNs employed in one Canadian province. Data were collected with the following scales: Emotional Climate, Practice Issues, Collaborative Relations, Psychological Contract Violation, General Job Satisfaction, Organizational Commitment Questionnaire, and Intent to Stay.

FINDINGS

The response rate was 29.4%. Most respondents were middle aged and diploma prepared, were in their current positions for 5 years or more, had 10 or more years of nursing experience, and worked full time. Despite moderate levels of job satisfaction, RNs held negative perceptions of culture (emotional climate, practice-related issues, and collaborative relations), trust, and commitment and were unlikely to stay with current employers. Structural equation modeling provided support for the impact of culture, trust, and satisfaction on commitment and partial support for intent to stay, explaining 45 and 31% of the variance, respectively.

PRACTICE IMPLICATIONS

The development and implementation of policies and interventions aimed at creating more supportive work environments and greater trust in employers and job satisfaction have merit. The most obvious benefit from such strategic interventions is the potential for improving RNs' organizational commitment and reducing turnover intentions.

MLH1 -93G>A promoter polymorphism and the risk of microsatellite-unstable colorectal cancer

BACKGROUND

Although up to 30% of patients with colorectal cancer have a positive family history of colorectal neoplasia, few colorectal cancers can be explained by mutations in high-penetrance genes. We investigated whether polymorphisms in DNA mismatch repair genes are associated with the risk of colorectal cancer.

METHODS

We genotyped 929 case patients and 1098 control subjects from Ontario and 430 case patients and 275 control subjects from Newfoundland and Labrador for five polymorphisms in the mismatch repair genes MLH1 and MSH2 with the fluorogenic 5' nuclease assay. Tumor microsatellite instability (MSI) was determined with a polymerase chain reaction-based method; MSI status was assigned as high (MSI-H, > or = 30% unstable markers among all markers tested), low (MSI-L, <30% markers unstable), or stable (MSS, no unstable markers). We used unconditional logistic regression to evaluate the association between each polymorphism and colorectal cancer after adjusting for age and sex. The associations between polymorphisms and tumor clinicopathologic features were evaluated with a Pearson's chi-square or Fisher's exact test. All statistical tests were two-sided.

RESULTS

We observed strong associations between the MLH1 -93G>A polymorphism and MSI-H tumors among case patients from Ontario (P = .001) and Newfoundland (P = .003). When compared with the control populations, homozygosity for the MLH1 -93G>A variant allele was associated with MSI-H tumors among case patients in Ontario (adjusted odds ratio [OR] = 3.23, 95% confidence interval [CI] = 1.65 to 6.30) and in Newfoundland (OR = 8.88, 95% CI = 2.33 to 33.9), as was heterozygosity among case patients in Ontario (OR = 1.84, 95% CI = 1.20 to 2.83) and in Newfoundland (OR = 2.56, 95% CI = 1.14 to 5.75). Genotype frequencies were similar among case patients with MSS and MSI-L tumors and control subjects, and the majority of homozygous variant carriers had MSS tumors. Among case patients from Ontario, an association between the MLH1 -93G>A polymorphism and a strong family history of colorectal cancer (for Amsterdam criteria I and II, P = .004 and P = .02, respectively) was observed.

CONCLUSION

In two patient populations, the MLH1 -93G>A polymorphism was associated with an increased risk of MSI-H colorectal cancer.