Patrick S Parfrey

Palo Alto University, إاست بالو ألتو، سان ماتيو، كاليفورنيا, California, United States

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Publications (353)2538.01 Total impact

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    ABSTRACT: Before the introduction of erythropoiesis-stimulating agents (ESAs) in 1989, repeated transfusions given to patients with end-stage renal disease caused iron overload, and the need for supplemental iron was rare. However, with the widespread introduction of ESAs, it was recognized that supplemental iron was necessary to optimize hemoglobin response and allow reduction of the ESA dose for economic reasons and recent concerns about ESA safety. Iron supplementation was also found to be more efficacious via intravenous compared to oral administration, and the use of intravenous iron has escalated in recent years. The safety of various iron compounds has been of theoretical concern due to their potential to induce iron overload, oxidative stress, hypersensitivity reactions, and a permissive environment for infectious processes. Therefore, an expert group was convened to assess the benefits and risks of parenteral iron, and to provide strategies for its optimal use while mitigating the risk for acute reactions and other adverse effects.
    Full-text · Article · Jan 2016 · Kidney International
  • Patrick S. Parfrey · Brendan J. Barrett
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    ABSTRACT: Atherosclerotic events, congestive heart failure and sudden cardiac death occur frequently in CKD patients. CKD is a risk factor for incident cardiovascular events and an adverse prognostic factor if a cardiovascular event occurs. Diminution in GFR is associated with modification of atherogenic, arteriosclerotic and cardiomyopathic processes at multiple levels. Cardiovascular risk factors include traditional atherogenic and CKD-related metabolic and hemodynamic risk factors. Risk factor intervention includes control of blood pressure, RAAS blockade, treatment of dyslipidemias, smoking cessation, antiplatelet therapies and control of hyperglycemia. Individualization of therapy is necessary as benefits and harms exist for each treatment. Efficacious treatments for congestive heart failure and atherosclerotic disease are available. The indications for coronary artery bypass graft surgery or percutaneous vascular stenting for atherosclerotic stenotic disease are the same regardless of renal function, but the outcomes are worse in CKD than in non-CKD patients.
    No preview · Chapter · Dec 2015
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    ABSTRACT: The population of the province of Newfoundland and Labrador (NL) has been a resource for genetic studies because of its historical isolation and increased prevalence of several monogenic disorders. Controversy remains regarding the genetic substructure and the extent of genetic homogeneity, which have implications for disease gene mapping. Population substructure has been reported from other isolated populations such as Iceland, Finland and Sardinia. We undertook this study to further our understanding of the genetic architecture of the NL population. We enrolled 494 individuals randomly selected from NL. Genome-wide SNP data were analyzed together with that from 14 other populations including HapMap3, Ireland, Britain and Native American samples from the Human Genome Diversity Project. Using multidimensional scaling and admixture analysis, we observed that the genetic structure of the NL population resembles that of the British population but can be divided into three clusters that correspond to religious/ethnic origins: Protestant English, Roman Catholic Irish and North American aboriginals. We observed reduced heterozygosity and an increased inbreeding coefficient (mean=0.005), which corresponds to that expected in the offspring of third-cousin marriages. We also found that the NL population has a significantly higher number of runs of homozygosity (ROH) and longer lengths of ROH segments. These results are consistent with our understanding of the population history and indicate that the NL population may be ideal for identifying recessive variants for complex diseases that affect populations of European origin.European Journal of Human Genetics advance online publication, 16 December 2015; doi:10.1038/ejhg.2015.256.
    No preview · Article · Dec 2015 · European journal of human genetics: EJHG
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    ABSTRACT: The effect of the calcimimetic cinacalcet on cardiovascular disease in patients undergoing hemodialysis with secondary hyperparathyroidism was assessed in the Evaluation of Cinacalcet Hydrochloride Therapy to Lower Cardiovascular Events trial. This was the largest (in size) and longest (in duration) randomized controlled clinical trial undertaken in this population. During planning, execution, analysis, and reporting of the trial, many lessons were learned, including those related to the use of a composite cardiovascular primary endpoint, definition of endpoints (particularly heart failure and severe unremitting hyperparathyroidism), importance of age for optimal stratification at randomization, use of unadjusted and adjusted intention-to-treat analysis for the primary outcome, how to respond to a lower-than-predicted event rate during the trial, development of a prespecified analytic plan that accounted for nonadherence and for cointerventions that diminished the power of the trial to observe a treatment effect, determination of the credibility of a subgroup effect, use of adverse effects database to investigate rare diseases, collection of blood for biomarker measurement not designated before trial initiation, and interpretation of the benefits-to-harms ratio for individual patients. It is likely that many of these issues will arise in the planning of future trials in CKD.
    No preview · Article · Nov 2015 · Clinical Journal of the American Society of Nephrology
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    ABSTRACT: Among patients receiving hemodialysis, abnormalities in calcium regulation have been linked to an increased risk of cardiovascular events. Cinacalcet lowers serum calcium concentrations through its effect on parathyroid hormone secretion and has been hypothesized to reduce the risk of cardiovascular events. In observational cohort studies, prescriptions of low dialysate calcium concentration and larger observed serum-dialysate calcium gradients have been associated with higher risks of in-dialysis facility or peri-dialytic sudden cardiac arrest. We performed this study to examine the risks associated with dialysate calcium and serum-dialysate gradients among participants in the Evaluation of Cinacalcet Hydrochloride Therapy to Lower Cardiovascular Events (EVOLVE) trial. In EVOLVE, 3883 hemodialysis patients were randomized 1:1 to cinacalcet or placebo. Dialysate calcium was administered at the discretion of treating physicians. We examined whether baseline dialysate calcium concentration or the serum-dialysate calcium gradient modified the effect of cinacalcet on the following adjudicated endpoints: (1) primary composite endpoint (death or first non-fatal myocardial infarction, hospitalization for unstable angina, heart failure, or peripheral vascular event); (2) cardiovascular death; and (3) sudden death. In EVOLVE, use of higher dialysate calcium concentrations was more prevalent in Europe and Latin America compared with North America. There was a significant fall in serum calcium concentration in the cinacalcet group; dialysate calcium concentrations were changed infrequently in both groups. There was no association between baseline dialysate calcium concentration or serum-dialysate calcium gradient and the endpoints examined. Neither the baseline dialysate calcium nor the serum-dialysate calcium gradient significantly modified the effects of cinacalcet on the outcomes examined. The effects of cinacalcet on cardiovascular death and major cardiovascular events are not altered by the dialysate calcium prescription and serum-dialysate calcium gradient.
    No preview · Article · Nov 2015 · Hemodialysis International
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    ABSTRACT: Background Previous economic evaluations of cinacalcet in patients with secondary hyperparathyroidism (sHPT) relied on the combination of surrogate end points in clinical trials and epidemiologic studies. Objectives The objective was to conduct an economic evaluation of cinacalcet on the basis of the EValuation Of Cinacalcet HCl Therapy to Lower CardioVascular Events (EVOLVE) trial from a US payer perspective. Methods We developed a semi-Markov model to assess the cost-effectiveness of cinacalcet in addition to conventional therapy, compared with conventional therapy alone, in patients with moderate-to-severe sHPT receiving hemodialysis. We used treatment effect estimates from the unadjusted intent-to-treat (ITT) analysis and prespecified covariate-adjusted ITT analysis as our main analyses. We assessed model sensitivity to variations in individual inputs and overall decision uncertainty through probabilistic sensitivity analyses. Results The incremental cost-effectiveness ratio (ICER) for cinacalcet was $61,705 per life-year and $79,562 per quality-adjusted life-year (QALY) gained using the covariate-adjusted ITT analysis. Probabilistic sensitivity analysis suggested a 73.2% chance of the ICER being below a willingness-to-pay threshold of $100,000. Treatment effects from unadjusted ITT analysis yielded an ICER of $115,876 per QALY. The model was most sensitive to the treatment effect on mortality. Conclusions In the unadjusted ITT analysis, cinacalcet does not represent a cost- effective use of health care resources when applying a willingness-to-pay threshold of $100,000 per QALY. When using the covariate-adjusted ITT treatment effect, which represents the least biased estimate, however, cinacalcet is a cost-effective therapy for patients with moderate-to-severe sHPT on hemodialysis.
    No preview · Article · Oct 2015 · Value in Health
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    ABSTRACT: Several published studies identified associations of a number of polymorphisms with a variety of survival outcomes in colorectal cancer. In this study, we aimed to explore 102 previously reported common genetic polymorphisms and their associations with overall survival (OS) and disease-free survival (DFS) in a colorectal cancer patient cohort from Newfoundland (n = 505). Genotypes were obtained using a genomewide SNP genotyping platform. For each polymorphism, the best possible genetic model was estimated for both overall survival and disease-free survival using a previously published approach. These SNPs were then analyzed under their genetic models by Cox regression method. Correction for multiple comparisons was performed by the False Discovery Rate (FDR) method. Univariate analysis results showed that RRM1-rs12806698, IFNGR1-rs1327474, DDX20-rs197412, and PTGS2-rs5275 polymorphisms were nominally associated with OS or DFS (p < 0.01). In stage-adjusted analysis, the nominal associations of DDX20-rs197412, PTGS2-rs5275, and HSPA5-rs391957 with DFS were detected. However, after FDR correction none of these polymorphisms remained significantly associated with the survival outcomes. We conclude that polymorphisms investigated in this study are not associated with OS or DFS in our colorectal cancer patient cohort.
    Full-text · Article · Jun 2015
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    ABSTRACT: -Patients with kidney disease have disordered bone and mineral metabolism including elevated serum concentrations of fibroblast growth factor 23 (FGF23). The latter are associated with cardiovascular and all-cause mortality. The objective was to determine the effects of the calcimimetic cinacalcet (versus placebo) on reducing serum FGF23 and whether changes in FGF23 are associated with death and cardiovascular events. -This was a secondary analysis of a randomized clinical trial comparing cinacalcet to placebo in addition to conventional therapy (phosphate binders/vitamin D) in patients receiving hemodialysis with secondary hyperparathyroidism (iPTH ≥ 300 pg/mL). The primary study end point was time to death or the first nonfatal cardiovascular event (myocardial infarction, hospitalization for angina, heart failure, or a peripheral vascular event). This analysis included 2985 patients (77% of randomized) with serum samples at baseline and 2602 (67%) patients with samples at both baseline and week 20. The results demonstrated a significantly larger proportion of patients randomized to cinacalcet had ≥30% (68% versus 28%) reductions in FGF23. Among patients randomized to cinacalcet, a ≥30% reduction in FGF23 between baseline and week 20 was associated with a nominally significant reduction in the primary composite endpoint (relative hazard (HR) 0.82; 95% confidence interval (95% CI) 0.69, 0.98), cardiovascular mortality (HR 0.66; 0.50, 0.87), sudden cardiac death (HR 0.57; 0.37, 0.86), and heart failure (HR 0.69; 0.48, 0.99). -Treatment with cinacalcet significantly lowers serum FGF23. Treatment-induced reductions in serum FGF23 are associated with lower rates of cardiovascular death and major cardiovascular events. Clinical Trial Registration Information-ClinicalTrials.gov. Identifier: NCT00345839.
    No preview · Article · Jun 2015 · Circulation
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    ABSTRACT: Patients with end-stage renal disease often have derangements in calcium and phosphorus homeostasis and resultant secondary hyperparathyroidism (sHPT), which may contribute to the high prevalence of arterial stiffness and hypertension. We conducted a secondary analysis of the Evaluation of Cinacalcet Hydrochloride Therapy to Lower Cardiovascular Events (EVOLVE) trial, in which patients receiving hemodialysis with sHPT were randomly assigned to receive cinacalcet or placebo. We sought to examine whether the effect of cinacalcet on death and major cardiovascular events was modified by baseline pulse pressure as a marker of arterial stiffness, and whether cinacalcet yielded any effects on blood pressure. As reported previously, an unadjusted intention-to-treat analysis failed to conclude that randomization to cinacalcet reduces the risk of the primary composite end point (all-cause mortality or non-fatal myocardial infarction, heart failure, hospitalization for unstable angina or peripheral vascular event). However, after prespecified adjustment for baseline characteristics, patients randomized to cinacalcet experienced a nominally significant 13% lower adjusted risk (95% confidence limit 4-20%) of the primary composite end point. The effect of cinacalcet was not modified by baseline pulse pressure (Pinteraction=0.44). In adjusted models, at 20 weeks cinacalcet resulted in a 2.2 mm Hg larger average decrease in systolic blood pressure (P=0.002) and a 1.3 mm Hg larger average decrease in diastolic blood pressure (P=0.002) compared with placebo. In summary, in the EVOLVE trial, the effect of cinacalcet on death and major cardiovascular events was independent of baseline pulse pressure.Journal of Human Hypertension advance online publication, 4 June 2015; doi:10.1038/jhh.2015.56.
    No preview · Article · Jun 2015 · Journal of human hypertension
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    ABSTRACT: Mitochondrion is a small organelle inside the eukaryotic cells. It has its own genome (mtDNA) and encodes for proteins that are critical for energy production and cellular metabolism. Mitochondrial dysfunctions have been implicated in cancer progression and may be related to poor prognosis in cancer patients. In this study we hypothesized that genetic variations in mtDNA are associated with clinical outcome in colorectal cancer patients. We tested the associations of six mtDNA polymorphisms [MitoT479C, MitoT491C, MitoT10035C, MitoA13781G, 10398 (A/G), and 16189 (T/C)] and the mtDNA copy number change with overall survival (OS) and disease-free survival (DFS) times. Two mtDNA polymorphisms were genotyped using the TaqMan(®) SNP genotyping technique and the genotypes for the remaining four mtDNA polymorphisms were obtained by the Illumina(®) HumanOmni1-Quad genome wide SNP genotyping platform in 536 patients. The mtDNA copy number change (in tumor tissues with respect to non-tumor tissues) was estimated using the quantitative real time polymerase chain reaction for 274 patients. Associations of these mtDNA variations with OS and DFS were tested using the Cox regression method. In both univariate and multivariable analyses, none of the six mtDNA polymorphisms were associated with OS or DFS. 39.6 and 60.4% of the patients had increased and decreased mtDNA copy number in their tumor tissues when compared to their non-tumor rectum or colon tissues, respectively. However, in contrast to previous findings, the change in the mtDNA copy number was associated with neither OS nor DFS in our patient cohort. Our results suggest that the mitochondrial genetic markers investigated in this study are not associated with outcome in colorectal cancer.
    Preview · Article · Jun 2015 · BMC Research Notes
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    ABSTRACT: The incidence of end-stage renal disease (ESRD) has been consistently shown to be higher among blacks and Hispanics compared to whites with unmeasured risk factors and access to care as suggested explanations. In a high-risk cohort with frequent protocol-directed follow-up, we evaluated the influence of race on cardiovascular (CV) outcomes and incidence of ESRD. TREAT was a randomized, double-blind, placebo-controlled study. This secondary analysis focused on role of race on outcomes. TREAT enrolled 4,038 patients with type 2 diabetes, chronic kidney disease (estimated glomerular filtration rate 20-60 mL/min per 1.73 m(2)), and anemia (hemoglobin level ≤11 g/dL) treated with either darbepoetin alfa or placebo. We compared self-described black and Hispanic patients to white patients with regard to baseline characteristics and outcomes, including mortality, CV outcomes (myocardial infarction, stroke, heart failure, resuscitated sudden death, and coronary revascularization), and incident ESRD. Multivariate adjusted Cox models were developed for these outcomes. Black and Hispanic patients were younger, more likely women, had less prior CV disease, and higher blood pressure. During a mean follow-up of 2.4 years with comparable access to care, blacks and Hispanics had a greater risk of ESRD but a significant lower risk of myocardial infarction and coronary revascularization than whites. After adjusting for confounders, blacks remained at significantly greater risk of ESRD than whites (hazard ratio 1.53, 95% CI 1.26-1.85, P < .001), whereas this ESRD risk did not persist among Hispanics. Despite similar access to care and lower CV event rates, the risk of ESRD was higher among blacks and Hispanics than whites. For blacks, but not Hispanics, this increase was independent of known attributable risk factors. Copyright © 2015 Elsevier Inc. All rights reserved.
    No preview · Article · May 2015 · American Heart Journal
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    Jürgen Floege · Yumi Kubo · Anna Floege · Glenn M Chertow · Patrick S Parfrey
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    ABSTRACT: Uncontrolled secondary hyperparathyroidism (sHPT) in patients with ESRD is a risk factor for calcific uremic arteriolopathy (CUA; calciphylaxis). Adverse event reports collected during the Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events trial were used to determine the frequency of CUA in patients receiving hemodialysis who had moderate to severe sHPT, as well as the effects of cinacalcet versus placebo. CUA events were collected while patients were receiving the study drug. Among the 3861 trial patients who received at least one dose of the study drug, 18 patients randomly assigned to placebo and six assigned to cinacalcet developed CUA (unadjusted relative hazard, 0.31; 95% confidence interval [95% CI], 0.13 to 0.79; P=0.014). Corresponding cumulative event rates (95% CI) at year 4 were 0.011% (0.006% to 0.018%) and 0.005% (0.002% to 0.010%). By multivariable analysis, other factors associated with CUA included female sex, higher body mass index, higher diastolic BP, and history of dyslipidemia or parathyroidectomy. Median (10%, 90% percentile) plasma parathyroid hormone concentrations proximal to the report of CUA were 796 (225, 2093) pg/ml and 410 (71, 4957) pg/ml in patients randomly assigned to placebo and cinacalcet, respectively. Active use of vitamin K antagonists was recorded in 11 of 24 patients with CUA, nine randomly assigned to placebo, and two to cinacalcet, in contrast to 5%-7% at any one time point in patients in whom CUA was not reported. Cinacalcet appeared to reduce the incidence of CUA in hemodialysis recipients who have moderate to severe sHPT. Copyright © 2015 by the American Society of Nephrology.
    Preview · Article · Apr 2015 · Clinical Journal of the American Society of Nephrology
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    ABSTRACT: Intention-to-treat (ITT) analysis is widely used to establish efficacy in randomized clinical trials. However, in a long-term outcomes study where non-adherence to study drug is substantial, the on-treatment effect of the study drug may be underestimated using the ITT analysis. The analyses presented herein are from the EVOLVE trial, a double-blind, placebo-controlled, event-driven cardiovascular outcomes study conducted to assess whether a treatment regimen including cinacalcet compared with placebo in addition to other conventional therapies reduces the risk of mortality and major cardiovascular events in patients receiving hemodialysis with secondary hyperparathyroidism. Pre-specified sensitivity analyses were performed to assess the impact of non-adherence on the estimated effect of cinacalcet. These analyses included lag-censoring, inverse probability of censoring weights (IPCW), rank preserving structural failure time model (RPSFTM) and iterative parameter estimation (IPE). The relative hazard (cinacalcet versus placebo) of mortality and major cardiovascular events was 0.93 (95% confidence interval 0.85, 1.02) using the ITT analysis; 0.85 (0.76, 0.95) using lag-censoring analysis; 0.81 (0.70, 0.92) using IPCW; 0.85 (0.66, 1.04) using RPSFTM and 0.85 (0.75, 0.96) using IPE. These analyses, while not providing definitive evidence, suggest that the intervention may have an effect while subjects are receiving treatment. The ITT method remains the established method to evaluate efficacy of a new treatment; however, additional analyses should be considered to assess the on-treatment effect when substantial non-adherence to study drug is expected or observed. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
    No preview · Article · Apr 2015 · Pharmaceutical Statistics
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    ABSTRACT: Hemodialysis (HD) is the main form of renal replacement therapy for many patients with end-stage renal disease. The purpose of this research is to assess reliability and validity of the Patient's Perception of Hemodialysis Scale. Using a cross-sectional design and a convenient sample (n = 236), psychometric properties of the PPHS were examined. Validity was assessed using factor analysis and Pearson's correlation. Reliability was determined using Cronbach's alpha and test-retest stability (n = 30). Validity and reliability was supported. Examination of the PPHS provides evidence that it is a valid and reliable instrument for measuring disease-specific concerns with the HD patients, assessing how people experience life, and identifying ways in which people interpret the meaning of their physical and psychosocial health and adaptation to life on HD.
    No preview · Article · Apr 2015 · Journal of Nursing Measurement
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    ABSTRACT: In this study we performed genome-wide association studies to identify candidate SNPs that may predict the risk of disease outcome in colorectal cancer. Patient cohort consisted of 505 unrelated patients with Caucasian ancestry. Germline DNA samples were genotyped using the Illumina® human Omni-1quad SNP chip. Associations of SNPs with overall and disease free survivals were examined primarily for 431 patients with microsatellite instability-low (MSI-L) or stable (MSS) colorectal tumors using Cox proportional hazards method adjusting for clinical covariates. Bootstrap method was applied for internal validation of results. As exploratory analyses, association analyses for the colon (n = 334) and rectal (n = 171) cancer patients were also performed. As a result, there was no SNP that reached the genomewide significance levels (p < 5x10(-8)) in any of the analyses. A small number of genetic markers (n = 10) showed nominal associations (p <10(-6)) for MSS/MSI-L, colon, or rectal cancer patient groups. These markers were located in two non-coding RNA genes or intergenic regions and none were amino acid substituting polymorphisms. Bootstrap analysis for the MSS/MSI-L cohort data suggested the robustness of the observed nominal associations. Likely due to small number of patients, our study did not identify an acceptable level of association of SNPs with outcome in MSS/MSI-L, colon, or rectal cancer patients. A number of SNPs with sub-optimal p-values were, however, identified; these loci may be promising and examined in other larger-sized patient cohorts.
    Full-text · Article · Mar 2015
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    ABSTRACT: The calcimimetic cinacalcet reduced the risk of death or cardiovascular (CV) events in older, but not younger, patients with moderate to severe secondary hyperparathyroidism (HPT) who were receiving hemodialysis. To determine whether the lower risk in younger patients might be due to lower baseline CV risk and more frequent use of cointerventions that reduce parathyroid hormone (kidney transplantation, parathyroidectomy, and commercial cinacalcet use), this study examined the effects of cinacalcet in older (≥65 years, n=1005) and younger (<65 years, n=2878) patients. Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events (EVOLVE) was a global, multicenter, randomized placebo-controlled trial in 3883 prevalent patients on hemodialysis, whose outcomes included death, major CV events, and development of severe unremitting HPT. The age subgroup analysis was prespecified. Older patients had higher baseline prevalence of diabetes mellitus and CV comorbidity. Annualized rates of kidney transplantation and parathyroidectomy were >3-fold higher in younger relative to older patients and were more frequent in patients randomized to placebo. In older patients, the adjusted relative hazard (95% confidence interval) for the primary composite (CV) end point (cinacalcet versus placebo) was 0.70 (0.60 to 0.81); in younger patients, the relative hazard was 0.97 (0.86 to 1.09). Corresponding adjusted relative hazards for mortality were 0.68 (0.51 to 0.81) and 0.99 (0.86 to 1.13). Reduction in the risk of severe unremitting HPT was similar in both groups. In the EVOLVE trial, cinacalcet decreased the risk of death and of major CV events in older, but not younger, patients with moderate to severe HPT who were receiving hemodialysis. Effect modification by age may be partly explained by differences in underlying CV risk and differential application of cointerventions that reduce parathyroid hormone. Copyright © 2015 by the American Society of Nephrology.
    Full-text · Article · Feb 2015 · Clinical Journal of the American Society of Nephrology
  • Robert N Foley · Patrick S Parfrey
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    ABSTRACT: Quality-of-life (QoL) outcomes are important elements of randomized controlled trials. The instruments for measurement of QoL vary but usually multiple comparisons are possible, a concern that can be offset by prespecifying the outcomes of interest. Missing data may threaten the validity of QoL assessments in trials. Therefore familiarity with the strategies used to account for missing data is necessary. Measures that incorporate both survival and QoL are helpful for treatment decisions. The definition of minimal clinically important differences in QoL scores is important and often derived using inadequate methods.
    No preview · Article · Feb 2015 · Methods in molecular biology (Clifton, N.J.)
  • Susan Stuckless · Patrick S Parfrey
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    ABSTRACT: Clinical epidemiological research in genetic diseases entails 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 to 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 also to be able to assess their impact on the magnitude and direction of the observed effect. The following chapter reviews the epidemiological concepts of selection bias, information bias, and confounding and discusses ways in which these sources of bias can be minimized.
    No preview · Article · Feb 2015 · Methods in molecular biology (Clifton, N.J.)
  • Patrick S Parfrey
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    ABSTRACT: The intention-to-treat analysis is the gold standard for evaluating efficacy in a randomized controlled trial. However, when non-adherence to randomized treatments is high, the actual treatment effect may be underestimated. The impact of drop-out from the intervention group or drop-in to the control group may be controlled by trial design, increasing the sample size, effective study execution, and a prespecified analytical plan to take contamination into account.These analyses may include censoring at time of co-interventions associated with stopping treatment, lag censoring which allows an additional period after discontinuation of study treatment to account for residual treatment effects, inverse probability of censoring weights (IPCW), accelerated failure time models, and contamination adjusted intent-to-treat analysis. These methods are particularly useful in assessing the "prescribed efficacy" of the study treatment, which can aid clinical decision-making.
    No preview · Article · Feb 2015 · Methods in molecular biology (Clifton, N.J.)
  • Bryan M Curtis · Brendan J Barrett · Patrick S Parfrey
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    ABSTRACT: 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 control trial include emphasis on the principal research question, randomization, blinding; definitions of outcome measures, of inclusion and exclusion criteria, and of comorbid and confounding factors; enrolling an adequate sample size; planning data management and analysis; preventing challenges to trial integrity such as drop-out, 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.
    No preview · Article · Feb 2015 · Methods in molecular biology (Clifton, N.J.)

Publication Stats

25k Citations
2,538.01 Total Impact Points

Institutions

  • 2015
    • Palo Alto University
      • Department of Medicine
      إاست بالو ألتو، سان ماتيو، كاليفورنيا, California, United States
    • Newfoundland and Labrador Centre for Health Information
      Saint John's, Newfoundland and Labrador, Canada
  • 2012-2015
    • Health Canada
      • Health Sciences Center
      Ottawa, Ontario, Canada
  • 1986-2015
    • Memorial University of Newfoundland
      • • Faculty of Medicine
      • • Division of Nephrology
      Saint John's, Newfoundland and Labrador, Canada
  • 2007
    • University of Toronto
      • Laboratory Medicine Program
      Toronto, Ontario, Canada
    • Samuel Lunenfeld Research Institute
      Toronto, Ontario, Canada
  • 2004
    • Washington University in St. Louis
      • Department of Genetics
      Saint Louis, MO, United States
  • 2002
    • University of Birmingham
      Birmingham, England, United Kingdom
    • University of Manitoba
      Winnipeg, Manitoba, Canada
  • 1999-2000
    • Boston University
      • Section of Preventive Medicine and Epidemiology
      Boston, Massachusetts, United States
  • 1998
    • Toronto Western Hospital
      Toronto, Ontario, Canada
  • 1996
    • Florida Memorial University
      Saint John, Indiana, United States
  • 1995
    • Dalhousie University
      • Department of Medicine
      Halifax, Nova Scotia, Canada
  • 1984-1986
    • McGill University
      • Department of Pathology
      Montréal, Quebec, Canada