Clinical trials are the main method for evaluating safety and efficacy of medical interventions and have produced many advances in improving human health. The Women’s Health Initiative overturned a half-century of harmful practice in hormone therapy, the National Lung Screening Trial identified the first successful lung cancer screening tool and the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial overturned decades-long assumptions. While some trials identify unforeseen safety issues or harms, many fail to demonstrate efficacy. Large trials require substantial resources; to ensure reliable outcomes, we must seek ways to improve the predictive information used as the basis of trials.
Here we demonstrate a modeling framework for linking knowledge of underlying biological mechanism to evaluate the expectation of trial outcomes. Key features include the ability to propagate uncertainty in biological mechanism to uncertainty in trial outcome and mechanisms for identifying knowledge gaps most responsible for unexpected outcomes. The framework was used to model the effect of selenium supplementation for prostate cancer prevention and parallels the Selenium and Vitamin E Cancer Prevention Trial that showed no efficacy despite suggestive data from secondary endpoints in the Nutritional Prevention of Cancer trial and found increased incidence of high-grade prostate cancer in certain subgroups.
Using machine learning methods, we identified the parameters of the model that are most predictive of trial outcome and found that the top four are directly related to the rates of reactions producing methylselenol and transporting extracellular selenium into the cell as selenide. This modeling process demonstrates how the approach can be used in advance of a large clinical trial to identify the best targets for conducting further research to reduce the uncertainty in the trial outcome.
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The online version of this article (doi:10.1186/s12918-014-0140-0) contains supplementary material, which is available to authorized users.
Multilevel modeling; Clinical trials; Decision support; Value of information (VOI); Cancer chemoprevention
Although an estimated 50% of adults in the United States consume dietary supplements, analytically substantiated data on their bioactive constituents are sparse. Several programs funded by the Office of Dietary Supplements (ODS) at the National Institutes of Health enhance dietary supplement database development and help to better describe the quantitative and qualitative contributions of dietary supplements to total dietary intakes. ODS, in collaboration with the United States Department of Agriculture, is developing a Dietary Supplement Ingredient Database (DSID) verified by chemical analysis. The products chosen initially for analytical verification are adult multivitamin-mineral supplements (MVMs). These products are widely used, analytical methods are available for determining key constituents, and a certified reference material is in development. Also MVMs have no standard scientific, regulatory, or marketplace definitions and have widely varying compositions, characteristics, and bioavailability. Furthermore, the extent to which actual amounts of vitamins and minerals in a product deviate from label values is not known. Ultimately, DSID will prove useful to professionals in permitting more accurate estimation of the contribution of dietary supplements to total dietary intakes of nutrients and better evaluation of the role of dietary supplements in promoting health and well-being. ODS is also collaborating with the National Center for Health Statistics to enhance the National Health and Nutrition Examination Survey dietary supplement label database. The newest ODS effort explores the feasibility and practicality of developing a database of all dietary supplement labels marketed in the US. This article describes these and supporting projects.
Dietary supplements; Analytical substantiation; Dietary supplement composition; Dietary supplement ingredient database; NHANES; DSID; NHANES-DSLD; DSLD-USA; Dietary supplement labels; Standard reference materials®; Certified reference materials
Several activities of the Office of Dietary Supplements (ODS) at the National Institutes of Health involve enhancement of dietary supplement databases. These include an initiative with US Department of Agriculture to develop an analytically substantiated dietary supplement ingredient database (DSID) and collaboration with the National Center for Health Statistics to enhance the dietary supplement label database in the National Health and Nutrition Examination Survey (NHANES). The many challenges that must be dealt with in developing an analytically supported DSID include categorizing product types in the database, identifying nutrients, and other components of public health interest in these products and prioritizing which will be entered in the database first. Additional tasks include developing methods and reference materials for quantifying the constituents, finding qualified laboratories to measure the constituents, developing appropriate sample handling procedures, and finally developing representative sampling plans. Developing the NHANES dietary supplement label database has other challenges such as collecting information on dietary supplement use from NHANES respondents, constant updating and refining of information obtained, developing default values that can be used if the respondent cannot supply the exact supplement or strength that was consumed, and developing a publicly available label database. Federal partners and the research community are assisting in making an analytically supported dietary supplement database a reality.
Dietary supplements; Analytical substantiation; Dietary supplement composition; Dietary supplement ingredient database; NHANES; DSID; Dietary supplement labels; Certified reference materials; Standard reference materials
A trans-National Institutes of Health initiative, Nutrition and Dietary Supplement Interventions for Inborn Errors of Metabolism (NDSI-IEM), was launched in 2010 to identify gaps in knowledge regarding the safety and utility of nutritional interventions for the management of inborn errors of metabolism (IEM) that need to be filled with evidence-based research. IEM include inherited biochemical disorders in which specific enzyme defects interfere with the normal metabolism of exogenous (dietary) or endogenous protein, carbohydrate, or fat. For some of these IEM, effective management depends primarily on nutritional interventions. Further research is needed to demonstrate the impact of nutritional interventions on individual health outcomes and on the psychosocial issues identified by patients and their families. A series of meetings and discussions were convened to explore the current United States’ funding and regulatory infrastructure and the challenges to the conduct of research for nutritional interventions for the management of IEM. Although the research and regulatory infrastructure are well-established, a collaborative pathway that includes the professional and advocacy rare disease community and federal regulatory and research agencies will be needed to overcome current barriers.
Inborn errors of metabolism; Newborn screening; Genetic; Rare diseases; Dietary supplements; Medical foods
The Office of Dietary Supplements (ODS) and the National Center for Complementary and Alternative Medicine (NCCAM) were both established by Congress in the 1990’s. ODS aims to strengthen knowledge and understanding of dietary supplements (DS). NCCAM promotes exploration of complementary and alternative medicine in the context of rigorous science. Together, they developed the Botanical Research Centers Program to promote interdisciplinary study of botanicals, particularly those found in DS, by supporting research activities ranging from plant and characterization to preclinical and early-phase clinical studies. These Centers are part of the coordinated efforts of ODS and NCCAM to enhance botanical research.
The National Institute of Standards and Technology (NIST), in collaboration with the National Institutes of Health’s Office of Dietary Supplements (NIH-ODS), has developed a Standard Reference Material (SRM) for the determination of 25-hydroxyvitamin D [25(OH)D] in serum. SRM 972 Vitamin D in Human Serum consists of four serum pools with different levels of vitamin D metabolites and has certified and reference values for 25(OH)D2, 25(OH)D3, and 3-epi-25(OH)D3. Value assignment of this SRM was accomplished using a combination of three isotope-dilution mass spectrometry approaches, with measurements performed at NIST and at the Centers for Disease Control and Prevention (CDC). Chromatographic resolution of the 3-epimer of 25(OH)D3 proved to be essential for accurate determination of the metabolites.
Increased interest in the potential societal benefit of incorporating health economics as a part of clinical translational science, particularly nutrition interventions, led the Office of Dietary Supplements at the National Institutes of Health to sponsor a conference to address key questions about economic analysis of nutrition interventions to enhance communication among health economic methodologists, researchers, reimbursement policy makers, and regulators. Issues discussed included the state of the science, such as what health economic methods are currently used to judge the burden of illness, interventions, or health care policies, and what new research methodologies are available or needed to address knowledge and methodological gaps or barriers. Research applications included existing evidence-based health economic research activities in nutrition that are ongoing or planned at federal agencies. International and U.S. regulatory, policy and clinical practice perspectives included a discussion of how research results can help regulators and policy makers within government make nutrition policy decisions, and how economics affects clinical guideline development.
cost-benefit analysis; primary prevention; nutrition policy; medical economics; nutrition therapy
The National Health and Nutrition Examination Survey (NHANES) provides the most comprehensive assessment of the health and nutrition status of the US population. Up-to-date reference intervals on biomarkers and dietary intake inform the scientific and public health policy communities on current status and trends over time.
The main purpose of dietary assessment methods such as the food-frequency questionnaire, food record (or diary), and 24-hr dietary recall is to estimate intake of nutrients and, together with supplement usage information, describe total intake of various foods or nutrients. As with all self-reporting methods, these tools are challenging to use and interpret. Yet, they are needed to establish dietary reference intake recommendations and to evaluate what proportion of the population meets these recommendations. While biomarkers are generally expensive and, to some degree, invasive, there is no question as to their ability to assess nutrition status. In some cases biomarkers can also be used to assess intake or function, although rarely can one biomarker fulfill all these purposes. For example, serum folate is a good indicator of folate intake, red blood cell (RBC) folate is a good status indicator, and plasma total homocysteine is a good functional indicator of one-carbon metabolism.
Using folate and vitamin D – two vitamins that are currently hotly debated in the public health arena – as two case studies, we discuss the complexities of using biomarkers and total intake information to assess nutrition status. These two examples also show how biomarkers and intake provide different information and how both are needed to evaluate and set public health policy. We also provide guidance on general requirements for using nutrition biomarkers and food and supplement intake information in longitudinal, population-based surveys.
nutrition survey; NHANES; monitoring; trend; biochemical indicator; nutrition status; food intake; dietary questionnaire; folate; vitamin D
A roundtable to discuss the measurement of folate status biomarkers in NHANES took place in July 2010. NHANES has measured serum folate since 1974 and red blood cell (RBC) folate since 1978 with the use of several different measurement procedures. Data on serum 5-methyltetrahydrofolate (5MTHF) and folic acid (FA) concentrations in persons aged ≥60 y are available in NHANES 1999–2002. The roundtable reviewed data that showed that folate concentrations from the Bio-Rad Quantaphase II procedure (Bio-Rad Laboratories, Hercules, CA; used in NHANES 1991–1994 and NHANES 1999–2006) were, on average, 29% lower for serum and 45% lower for RBC than were those from the microbiological assay (MA), which was used in NHANES 2007–2010. Roundtable experts agreed that these differences required a data adjustment for time-trend analyses. The roundtable reviewed the possible use of an isotope-dilution liquid chromatography–tandem mass spectrometry (LC-MS/MS) measurement procedure for future NHANES and agreed that the close agreement between the MA and LC-MS/MS results for serum folate supported conversion to the LC-MS/MS procedure. However, for RBC folate, the MA gave 25% higher concentrations than did the LC-MS/MS procedure. The roundtable agreed that the use of the LC-MS/MS procedure to measure RBC folate is premature at this time. The roundtable reviewed the reference materials available or under development at the National Institute of Standards and Technology and recognized the challenges related to, and the scientific need for, these materials. They noted the need for a commutability study for the available reference materials for serum 5MTHF and FA.
A roundtable to discuss the measurement of vitamin B-12 (cobalamin) status biomarkers in NHANES took place in July 2010. NHANES stopped measuring vitamin B-12–related biomarkers after 2006. The roundtable reviewed 3 biomarkers of vitamin B-12 status used in past NHANES—serum vitamin B-12, methylmalonic acid (MMA), and total homocysteine (tHcy)—and discussed the potential utility of measuring holotranscobalamin (holoTC) for future NHANES. The roundtable focused on public health considerations and the quality of the measurement procedures and reference methods and materials that past NHANES used or that are available for future NHANES. Roundtable members supported reinstating vitamin B-12 status measures in NHANES. They noted evolving concerns and uncertainties regarding whether subclinical (mild, asymptomatic) vitamin B-12 deficiency is a public health concern. They identified the need for evidence from clinical trials to address causal relations between subclinical vitamin B-12 deficiency and adverse health outcomes as well as appropriate cutoffs for interpreting vitamin B-12–related biomarkers. They agreed that problems with sensitivity and specificity of individual biomarkers underscore the need for including at least one biomarker of circulating vitamin B-12 (serum vitamin B-12 or holoTC) and one functional biomarker (MMA or tHcy) in NHANES. The inclusion of both serum vitamin B-12 and plasma MMA, which have been associated with cognitive dysfunction and anemia in NHANES and in other population-based studies, was preferable to provide continuity with past NHANES. Reliable measurement procedures are available, and National Institute of Standards and Technology reference materials are available or in development for serum vitamin B-12 and MMA.
A roundtable dialogue to discuss “NHANES Monitoring of Biomarkers of Folate and Vitamin B-12 Status” took place in July 2010. This article provides an overview of the meeting and this supplement issue. Although the focus of the roundtable dialogue was on the measurement of folate and vitamin B-12 status biomarkers in NHANES, this article also describes the relevance and importance of these issues for clinical and research laboratories. The roundtable identified the microbiological assay (MA) as the gold standard for measurement of serum and red blood cell folate concentrations. The roundtable noted that differences in results between the Bio-Rad Quantaphase II procedure (Bio-Rad Laboratories, Hercules, CA) that NHANES 1991–1994 and 1999–2006 used and the MA that NHANES 2007–2010 used will require adjustment equations to evaluate time trends. The roundtable found that the close agreement between the serum results for the MA and liquid chromatography–tandem mass spectrometry (LC-MS/MS) procedures supported the conversion to LC-MS/MS for serum folate in future NHANES. The roundtable recognized the uncertainty about whether subclinical vitamin B-12 deficiency is a public health concern but encouraged reinstatement of at least one circulating vitamin B-12 measure and one functional vitamin B-12 status measure in future NHANES. The use of serum vitamin B-12 and plasma methylmalonic acid would provide continuity with past NHANES. The roundtable supported the continued use of the National Institute of Standards and Technology (NIST) reference materials in NHANES biomarker analyses and the further development of additional reference materials by the NIST.