Surrogate disease markers as substitutes for chronic disease outcomes in studies of diet and chronic disease relations.

Surrogate biomarkers for clinical outcomes afford scientific and economic efficiencies when investigating nutritional interventions in chronic diseases. However, valid scientific results are dependent on the qualification of these disease markers that are intended to be substitutes for a clinical outcome and to accurately predict benefit or harm. In this article, we examine the challenges of evaluating surrogate markers and describe the framework proposed in a 2010 Institute of Medicine report. The components of this framework are presented in the context of nutritional interventions for chronic diseases. We present case studies of 2 well-accepted surrogate markers [blood pressure within sodium intake and cardiovascular disease (CVD) context and low density lipoprotein-cholesterol concentrations within a saturated fat and CVD context]. We also describe additional cases in which the evidence is insufficient to validate their surrogate status. Guidance is offered for future research that evaluates or uses surrogate markers.

Options for basing Dietary Reference Intakes (DRIs) on chronic disease endpoints: report from a joint US-/Canadian-sponsored working group.

Dietary Reference Intakes (DRIs) are used in Canada and the United States in planning and assessing diets of apparently healthy individuals and population groups. The approaches used to establish DRIs on the basis of classical nutrient deficiencies and/or toxicities have worked well. However, it has proved to be more challenging to base DRI values on chronic disease endpoints; deviations from the traditional framework were often required, and in some cases, DRI values were not established for intakes that affected chronic disease outcomes despite evidence that supported a relation. The increasing proportions of elderly citizens, the growing prevalence of chronic diseases, and the persistently high prevalence of overweight and obesity, which predispose to chronic disease, highlight the importance of understanding the impact of nutrition on chronic disease prevention and control. A multidisciplinary working group sponsored by the Canadian and US government DRI steering committees met from November 2014 to April 2016 to identify options for addressing key scientific challenges encountered in the use of chronic disease endpoints to establish reference values. The working group focused on 3 key questions: 1) What are the important evidentiary challenges for selecting and using chronic disease endpoints in future DRI reviews, 2) what intake-response models can future DRI committees consider when using chronic disease endpoints, and 3) what are the arguments for and against continuing to include chronic disease endpoints in future DRI reviews? This report outlines the range of options identified by the working group for answering these key questions, as well as the strengths and weaknesses of each option.

Inflammatory Bowel Disease: Epidemiology, Evaluation, Treatment, and Health Maintenance.

The incidence and prevalence of inflammatory bowel disease are rising. Crohn's disease and ulcerative colitis each have distinct features. Treatments are changing rapidly, and there are many new drugs in the pipeline. Health maintenance also plays a key role in the care of this patient population.

Using the PhenX Toolkit to Add Standard Measures to a Study.

The PhenX (consensus measures for Phenotypes and eXposures) Toolkit (https://www.phenxtoolkit.org/) offers high-quality, well-established measures of phenotypes and exposures for use by the scientific community. The goal is to promote the use of standard measures, enhance data interoperability, and help investigators identify opportunities for collaborative and translational research. The Toolkit contains 395 measures drawn from 22 research domains (fields of research), along with additional collections of measures for Substance Abuse and Addiction (SAA) research, Mental Health Research (MHR), and Tobacco Regulatory Research (TRR). Additional measures for TRR that are expected to be released in 2015 include Obesity, Eating Disorders, and Sickle Cell Disease. Measures are selected by working groups of domain experts using a consensus process that includes input from the scientific community. The Toolkit provides a description of each PhenX measure, the rationale for including it in the Toolkit, protocol(s) for collecting the measure, and supporting documentation. Users can browse measures in the Toolkit or can search the Toolkit using the Smart Query Tool or a full text search. PhenX Toolkit users select measures of interest to add to their Toolkit. Registered Toolkit users can save their Toolkit and return to it later to revise or complete. They then have options to download a customized Data Collection Worksheet that specifies the data to be collected, and a Data Dictionary that describes each variable included in the Data Collection Worksheet. The Toolkit also has a Register Your Study feature that facilitates cross-study collaboration by allowing users to find other investigators using the same PhenX measures.

The PhenX Toolkit pregnancy and birth collections.

PURPOSE: Pregnancy and childbirth are normal conditions, but complications and adverse outcomes are common. Both genetic and environmental factors influence the course of pregnancy. Genetic epidemiologic research into pregnancy outcomes could be strengthened by the use of common measures, which would allow data from different studies to be combined or compared. Here, we introduce perinatal researchers to the PhenX Toolkit and the Collections related to pregnancy and childbirth. METHODS: The Pregnancy and Birth Collections were drawn from measures in the PhenX Tooklit. The lead author selected a list of measures for each Collection, which was reviewed by the remaining authors and revised on the basis of their comments. We chose the measures we thought were most relevant for perinatal research and had been linked most strongly to perinatal outcomes. RESULTS: The Pregnancy and Birth Health Conditions Collection includes 24 measures related to pregnancy and fertility history, maternal complications, and infant complications. The Pregnancy and Birth Outcome Risk Factors Collection includes 43 measures of chemical, medical, psychosocial, and personal factors associated with pregnancy outcomes. CONCLUSIONS: The biological complexity of pregnancy and its sensitivity to environmental and genomic influences suggest that multidisciplinary approaches are needed to generate new insights or practical interventions. To fully exploit new research methods and resources, we encourage the biomedical research community to adopt standard measures to facilitate pooled or meta-analyses.

Using the PhenX Toolkit to Add Standard Measures to a Study.

The PhenX (consensus measures for Phenotypes and eXposures) Toolkit (https://www.phenxtoolkit.org/) offers high-quality, well-established measures of phenotypes and exposures for use by the scientific community. The Toolkit contains 295 measures drawn from 21 research domains (fields of research). The measures were selected by Working Groups of domain experts using a consensus process that included input from the scientific community. The Toolkit provides a description of each PhenX measure, the rationale for including it in the Toolkit, protocol(s) for collecting the measure, and supporting documentation. Users can browse by measures, domains, or collections, or can search the Toolkit using the Smart Query Tool. Once users have selected some measures, they can download a customized Data Collection Worksheet that specifies what information needs to be collected, and a Data Dictionary that describes each variable included in their Data Collection Worksheet. To help researchers find studies with comparable data, PhenX measures and variables are being mapped to studies in the database of Genotypes and Phenotypes (dbGaP).

The PhenX Toolkit: get the most from your measures.

The potential for genome-wide association studies to relate phenotypes to specific genetic variation is greatly increased when data can be combined or compared across multiple studies. To facilitate replication and validation across studies, RTI International (Research Triangle Park, North Carolina) and the National Human Genome Research Institute (Bethesda, Maryland) are collaborating on the consensus measures for Phenotypes and eXposures (PhenX) project. The goal of PhenX is to identify 15 high-priority, well-established, and broadly applicable measures for each of 21 research domains. PhenX measures are selected by working groups of domain experts using a consensus process that includes input from the scientific community. The selected measures are then made freely available to the scientific community via the PhenX Toolkit. Thus, the PhenX Toolkit provides the research community with a core set of high-quality, well-established, low-burden measures intended for use in large-scale genomic studies. PhenX measures will have the most impact when included at the experimental design stage. The PhenX Toolkit also includes links to standards and resources in an effort to facilitate data harmonization to legacy data. Broad acceptance and use of PhenX measures will promote cross-study comparisons to increase statistical power for identifying and replicating variants associated with complex diseases and with gene-gene and gene-environment interactions.

PhenX: a toolkit for interdisciplinary genetics research.

PURPOSE OF REVIEW: To highlight standard PhenX (consensus measures for Phenotypes and eXposures) measures for nutrition, dietary supplements, and cardiovascular disease research and to demonstrate how these and other PhenX measures can be used to further interdisciplinary genetics research. RECENT FINDINGS: PhenX addresses the need for standard measures in large-scale genomic research studies by providing investigators with high-priority, well established, low-burden measurement protocols in a web-based toolkit (https://www.phenxtoolkit.org). Cardiovascular and Nutrition and Dietary Supplements are just 2 of 21 research domains and accompanying measures included in the PhenX Toolkit. SUMMARY: Genome-wide association studies (GWAS) provide promise for the identification of genomic markers associated with different disease phenotypes, but require replication to validate results. Cross-study comparisons typically increase statistical power and are required to understand the roles of comorbid conditions and environmental factors in the progression of disease. However, the lack of comparable phenotypic, environmental, and risk factor data forces investigators to infer and to compare metadata rather than directly combining data from different studies. PhenX measures provide a common currency for collecting data, thereby greatly facilitating cross-study analysis and increasing statistical power for identification of associations between genotypes, phenotypes, and exposures.

Issues in the registration of clinical trials.

Public concerns about the perils associated with incomplete or delayed reporting of results from clinical trials has heightened interest in trial registries and results databases. Here we review the current status of trial registration efforts and the challenges in developing a comprehensive system of trial registration and reporting of results. ClinicalTrials.gov, the largest trial registry with 36 249 trials from approximately 140 countries, has procedures in place to help ensure that records are valid and informative. Key challenges include the need to minimize inadvertent duplicate registrations, to ensure that interventions have unambiguous names, and to have a search engine that identifies all trials that meet a user's specifications. Recent policy initiatives have called for the development of a database of trial results. Several issues confound the implementation of such a database, including the lack of an accepted format or process for providing summaries of trial results to the public and concerns about disseminating data in the absence of independent scientific review.

Enrolling research subjects from clinical practice: ethical and procedural issues in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial.

The Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial is a multi-site effectiveness study funded by the National Institute of Mental Health (NIMH) with the aim of identifying successful, acceptable and cost-effective treatment strategies for outpatients with unremitted depression. With enrollment of 4,041 adults with major depressive disorder (MDD), it is the largest controlled psychiatric treatment study ever undertaken. In the course of developing procedures to ensure that ambitious enrollment goals were met, a number of ethical and practical issues became apparent that underscore the conflicts between effectiveness research and human subject protections. These are delineated as they relate to study design; eligibility criteria; incentives to subjects; investigators and clinical sites; the complementary roles of clinical research coordinators (CRCs) and study clinicians; and recruitment and consent procedures. The STAR*D trial exemplifies the interplay and tension between those strategies that integrate research and clinical aims and roles in the service of enhancing external validity, site participation, and recruitment and retention versus those strategies that differentiate research and clinical treatment in the service of research integrity and human subject protections. We hope that a discussion of these key challenges and dilemmas and how they have been addressed will help inform future discussions concerning design and conduct of ethical effectiveness trials designed to optimize care in real world clinical settings.

Development of the metabolic syndrome in black and white adolescent girls: a longitudinal assessment.

BACKGROUND: The metabolic syndrome, associated with increased risk of type 2 diabetes mellitus and cardiovascular disease, begins to develop during adolescence. OBJECTIVE: We sought to identify early predictors of the presence of the syndrome at the ages of 18 and 19 years in black and white girls. METHODS: Using longitudinal data on participants from 2 centers in the National Heart, Lung, and Blood Institute Growth and Health Study, a 10-year cohort study, we applied cutoffs from the Adult Treatment Panel III to document changes in the prevalence of abnormal syndrome elements and the syndrome in girls aged 9 and 10 years, when cases were rare, and those aged 18 and 19 years, when prevalence had reached 3%. Longitudinal regression models identified early predictors for the presence of the syndrome. RESULTS: Only 1 girl of each race had > or =3 factors at ages 9 and 10 (0.2%), but 20 black girls (3.5%) and 12 white girls (2.3%) had the syndrome 10 years later. Low high-density lipoprotein cholesterol was prevalent throughout the period in both black and white girls. The prevalence of other variables was low at enrollment but increased during follow-up, except for abnormal triglyceride levels in black girls, which remained low throughout follow-up. In multivariate models, early measures of waist circumference and triglyceride level were significant predictors for development of the syndrome. CONCLUSION: The strong association of central adiposity with the development of the metabolic syndrome suggests that early interventions aimed at managing preteen obesity could reduce risk of developing the syndrome.

Obesity and the development of insulin resistance and impaired fasting glucose in black and white adolescent girls: a longitudinal study.

OBJECTIVE: Age at onset of type 2 diabetes has decreased during the past 20 years, especially in black women. Studies of factors associated with insulin resistance and hyperglycemia in preadolescent and adolescent populations are essential to understanding diabetes development. RESEARCH DESIGN AND METHODS: The National Heart, Lung, and Blood Institute (NHLBI) Growth and Health Study (NGHS) is a 10-year cohort study of the development of obesity in black and white girls. Two NGHS centers examined the associations of obesity, puberty, and race with fasting insulin, glucose, and homeostasis model assessment of insulin resistance (HOMA-IR; a calculated index of insulin resistance) measures at 9-10 years of age (baseline) and 10 years later. RESULTS: Black girls had greater baseline and year-10 BMI than white girls, with a greater 10-year incidence of obesity. BMI-insulin correlations were positive in both black and white girls at both visits, but insulin remained higher in black girls after controlling for BMI. In black girls, insulin and HOMA-IR were higher in the prepubertal period (before the emergence of racial differences in BMI), increased more during puberty, and decreased less with its completion. Baseline BMI predicted year-10 glucose and the development of impaired fasting glucose (IFG) in black girls. In white girls, the rate of BMI increase during follow-up predicted these outcomes. The 10-year incidence of diabetes in black girls was 1.4%. CONCLUSIONS: Black-white differences in insulin resistance are not just a consequence of obesity, but precede the pubertal divergence in BMI. The development of IFG appears to be a function of the rate of increase of BMI in white girls and early obesity in black girls.