The evolution of evidence hierarchies: what can Bradford Hill's 'guidelines for causation' contribute?

Is chronic rhinosinusitis related to allergic rhinitis in adults and children? Applying epidemiological guidelines for causation

The relationship between allergic rhinitis and chronic rhinosinusitis has been assessed in a number of observational and experimental studies. In this review, we attempt their synthesis and evaluation using the modified Bradford Hill guidelines for causation. Although there is no proof of causation, especially in the pediatric literature, an evaluation of underlying allergies is recommended at least as an initial measure of symptoms relief.

Until RCT proven? On the asymmetry of evidence requirements for risk assessment

The problem of collecting, analysing and evaluating evidence on adverse drug reactions is an example of the more general class of epistemological problems related to scientific inference and prediction, as well as a central problem of health care practice. Philosophical discussions have analysed critically the methodological pitfalls and epistemological implications of evidence assessment in medicine; however, they have focused predominantly on evidence of treatment efficacy. Most of this work is devoted to statistical methods of causal inference with a special focus on the privileged role assigned to randomized controlled trials (RCTs) in evidence-based medicine. Regardless of whether the RCT's privilege holds for efficacy assessment, it is nevertheless important to make a distinction between causal inference in relation to intended and unintended effects, in that the unknowns at stake are heterogeneous in the two contexts. This point has been emphasized by epidemiologists in the last decade. Their primary focus is methodological and regards the fact that bias and confounding factors do not affect studies on intended and unintended effects in the same way. However, deeper concerns ground the intuition for such a distinction; these are related to the constraints we impose on evidence and their epistemological justification. My thesis is that such constraints ought to be understood as being different in evidence for risk versus for efficacy. I present the recent debate on the causal association between acetaminophen and asthma in order to illustrate the point at issue. The upshot of my analysis is that different epistemologies confer different methodological choices, which in turn bring about relevant practical implications such as the decision to restrict or suspend drug use rather than leaving it on the market. Thus, it is worth considering the criteria underlying our evidence constraints because they may be ill suited to the purpose for which they are used.

Vitamin D: beyond bone

In recent years, vitamin D has been received increased attention due to the resurgence of vitamin D deficiency and rickets in developed countries and the identification of extraskeletal effects of vitamin D, suggesting unexpected benefits of vitamin D in health and disease, beyond bone health. The possibility of extraskeletal effects of vitamin D was first noted with the discovery of the vitamin D receptor (VDR) in tissues and cells that are not involved in maintaining mineral homeostasis and bone health, including skin, placenta, pancreas, breast, prostate and colon cancer cells, and activated T cells. However, the biological significance of the expression of the VDR in different tissues is not fully understood, and the role of vitamin D in extraskeletal health has been a matter of debate. This report summarizes recent research on the roles for vitamin D in cancer, immunity and autoimmune diseases, cardiovascular and respiratory health, pregnancy, obesity, erythropoiesis, diabetes, muscle function, and aging.

Current experience with applying the GRADE approach to public health interventions: an empirical study

BACKGROUND

The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach has been adopted by many national and international organisations as a systematic and transparent framework for evidence-based guideline development. With reference to an ongoing debate in the literature and within public health organisations, this study reviews current experience with the GRADE approach in rating the quality of evidence in the field of public health and identifies challenges encountered.

METHODS

We conducted semi-structured interviews with individuals/groups that have applied the GRADE approach in the context of systematic reviews or guidelines in the field of public health, as well as with representatives of groups or organisations that actively decided against its use. We initially contacted potential participants by email. Responses were obtained by telephone interview or email, and written interview summaries were validated with participants. We analysed data across individual interviews to distil common themes and challenges.

RESULTS

Based on 25 responses, we undertook 18 interviews and obtained 15 in-depth responses relating to specific systematic reviews or guideline projects; a majority of the latter were contributed by groups within the World Health Organization. All respondents that have used the GRADE approach appreciated the systematic and transparent process of assessing the quality of the evidence. However, respondents reported a range of minor and major challenges relating to complexity of public health interventions, choice of outcomes and outcome measures, ability to discriminate between different types of observational studies, use of non-epidemiological evidence, GRADE terminology and the GRADE and guideline development process. Respondents' suggestions to make the approach more applicable to public health interventions included revisiting terminology, offering better guidance on how to apply GRADE to complex interventions and making modifications to the current grading scheme.

CONCLUSIONS

Our findings suggest that GRADE principles are applicable to public health and well-received but also highlight common challenges. They provide a starting point for exploring options for improvements and, where applicable, testing these across different types of public health interventions. Several public health organisations are currently testing GRADE, and the GRADE Working Group is eager to engage with these groups to find ways to address concerns.

Pharmacovigilance

Adverse drug reactions are the fifth most frequent cause of deaths in developed countries, effectively a global epidemic. However, progress in ameliorating the problem has been slow. Pharmacovigilance currently operates without clear objectives in relation to individual decisions, with no protocol (although risk management plans are a great step forward), with obscure materials and methods used for making decisions, with very limited reasoning and discussion, and little or no follow up and audit of the results. Problems include under-reporting, poor quality reports, underuse of the latest communications technology and suboptimal individual feedback to reporters. Assessment of causality is poor, impeding decision-making. After signal detection, more active measures to assess the risk to public health are needed. Other essential factors include precision about the ways in which data are prepared and transformed into databases, the recognition of secondary effects, which may be more obvious than the primary effect, but not so easy to link causally, and cognisance of all kinds of interactions. Areas that should be developed include pharmacoepidemiology, knowledge finding (through data mining), and communication and systems technology. The general way forward seems clear: a rigorous way of documenting all the steps, from getting reports of harms into regulatory databases to assessing their effects on public health, is essential and should be publicly reviewed for weaknesses. In turn, matters would be much improved by input on benefit/harm perceptions from patient groups, influencing decisions about what should be the true targets for regulatory and pharmacovigilance activities, avoiding second guessing by regulators.

Nutrition issues in Codex: health claims, nutrient reference values and WTO agreements: a conference report

BACKGROUND

Codex documents may be used as educational and consensus materials for member governments. Also, the WTO SPS Agreement recognizes Codex as the presumptive international authority on food issues. Nutrient bioavailability is a critical factor in determining the ability of nutrients to provide beneficial effects. Bioavailability also influences the quantitative dietary requirements that are the basis of nutrient intake recommendations and NRVs.

HEALTH CLAIMS

Codex, EFSA and some national regulatory authorities have established guidelines or regulations that will permit several types of health claims. The scientific basis for claims has been established by the US FDA and EFSA, but not yet by Codex. Evidence-based nutrition differs from evidence-based medicine, but the differences are only recently gaining recognition. Health claims on foods may provide useful information to consumers, but many will interpret the information to mean that they can rely upon the food or nutrient to eliminate a disease risk.

NUTRIENT REFERENCE VALUES

NRVs are designed to provide a quantitative basis for comparing the nutritive values of foods, helping to illustrate how specific foods fit into the overall diet. The INL-98 and the mean of adult male and female values provide NRVs that are sufficient when used as targets for individual intakes by most adults.

WORLD TRADE ORGANIZATION AGREEMENTS

WTO recognizes Codex as the primary international authority on food issues. Current regulatory schemes based on recommended dietary allowances are trade restrictive. A substantial number of decisions by the EFSA could lead to violation of WTO agreements.

Is meta-analysis the platinum standard of evidence?

An astonishing volume and diversity of evidence is available for many hypotheses in the biomedical and social sciences. Some of this evidence-usually from randomized controlled trials (RCTs)-is amalgamated by meta-analysis. Despite the ongoing debate regarding whether or not RCTs are the 'gold-standard' of evidence, it is usually meta-analysis which is considered the best source of evidence: meta-analysis is thought by many to be the platinum standard of evidence. However, I argue that meta-analysis falls far short of that standard. Different meta-analyses of the same evidence can reach contradictory conclusions. Meta-analysis fails to provide objective grounds for intersubjective assessments of hypotheses because numerous decisions must be made when performing a meta-analysis which allow wide latitude for subjective idiosyncrasies to influence its outcome. I end by suggesting that an older tradition of evidence in medicine-the plurality of reasoning strategies appealed to by the epidemiologist Sir Bradford Hill-is a superior strategy for assessing a large volume and diversity of evidence.

Dose-response relationships in multifunctional food design: assembling the evidence

Demonstrating single and multiple functions attributable to foods or specific food components is a challenge. The International Life Sciences Institute Europe co-ordinated EU concerted actions, Functional Food Science in Europe (FUFOSE) and the Process for the Assessment of Scientific Support for Claims on Food (PASSCLAIM), respectively, addressed the soundness of the evidence and its coherence with a mechanistic schema comprising valid markers of exposure, intermediate and final outcomes and the quality and integrity of the evidence overall. Demonstrating causality often relies on randomized controlled trials (RCTs). However, in public health and biomedical science there is concern about the suitability of RCTs as sole standards of evidence-based approaches. Alternative and complementary approaches using updated Hill's viewpoints for appraising the evidence can be used in conjunction with evidence-based mechanistic reasoning and the quality criteria proposed in FUFOSE and PASSCLAIM to design studies and to assemble evidence exploring single or multiple benefits from food components and foods.

Preparing dossiers: strength of the evidence and problems of proof

In Europe, for authorisation of a health claim, applicants must follow the procedures in the legislation and in the guidelines for submission of a dossier set out by the European Food Safety Authority. The Functional Foods in Europe (FUFOSE) and Process for the Assessment of Scientific Support for Claims on Foods (PASSCLAIM) projects underpinned the laws and provided criteria against which the quality of the totality of the available data could be judged. Whereas the regulations and PASSCLAIM require an assessment of the extent to which cause and effect can be demonstrated between a food category, a food or constituent and a health benefit, the European Food Safety Authority requires conclusive evidence of cause and effect. This latter standard of proof and a focus on randomised controlled trials done on isolated components and using validated physiological biomarkers may not always be appropriate to assess nutrition science. The aims of this paper are to address the strengths and weaknesses of different sources of evidence that contribute to the totality of the available data, to undertake a critical examination of the application of a drug-like assessment model in evidence-based nutrition and to encourage research on new biomarkers of health and homeostatic adaptability. There is a need for (a) a robust and pragmatic scientific framework for assessing the strength, consistency and biological plausibility of the evidence, and (b) consumer understanding research on claims that use qualifying language and/or graphics to reflect the weight of evidence. Such scientific, policy and communication approaches are proportionate and could help stimulate academic research, promote fair trade and product innovation and contribute to consumer education about food and health.

Policies to clean up toxic industrial contaminated sites of Gela and Priolo: a cost-benefit analysis

BACKGROUND

Cost-benefit analysis is a transparent tool to inform policy makers about the potential effect of regulatory interventions, nevertheless its use to evaluate clean-up interventions in polluted industrial sites is limited. The two industrial areas of Gela and Priolo in Italy were declared "at high risk of environmental crisis" in 1990. Since then little has been done to clean the polluted sites and reduce the health outcomes attributable to pollution exposure. This study, aims to quantify the monetary benefits resulting from clean-up interventions in the contaminated sites of Gela and Priolo.

METHODS

A damage function approach was used to estimate the number of health outcomes attributable to industrial pollution exposure. Extensive one way analyses and probabilistic analyses were conducted to investigate the sensitivity of results to different model assumptions.

RESULTS

It has been estimated that, on average, 47 cases of premature death, 281 cases of cancer and 2,702 cases of non-cancer hospital admission could be avoided each year by removing environmental exposure in these two areas. Assuming a 20 year cessation lag and a 4% discount rate we calculate that the potential monetary benefit of removing industrial pollution is €3,592 million in Priolo and €6,639 million in Gela.

CONCLUSIONS

Given the annual number of health outcomes attributable to pollution exposure the effective clean-up of Gela and Priolo should be prioritised. This study suggests that clean-up policies costing up to €6,639 million in Gela and €3,592 million in Priolo would be cost beneficial. These two amounts are notably higher than the funds allocated thus far to clean up the two sites, €127.4 million in Gela and €774.5 million in Priolo, implying that further economic investments - even considerable ones - could still prove cost beneficial.

26th Hohenheim Consensus Conference, September 11, 2010 Scientific substantiation of health claims: evidence-based nutrition

OBJECTIVE

The objective was to define the term evidence based nutrition on the basis of expert discussions and scientific evidence.

METHODS AND PROCEDURES

The method used is the established Hohenheim Consensus Conference. The term "Hohenheim Consensus Conference" defines conferences dealing with nutrition-related topics. The major aim of the conference is to review the state of the art of a given topic with experts from different areas (basic science, clinicians, epidemiologists, etc.). Based on eight to 12 questions, the experts discuss short answers and try to come to a consensus. A scientifically based text is formulated that justifies the consensus answer. To discuss the requirements for the scientific substantiation of claims, the 26th Hohenheim Consensus Conference gathered the views of many academic experts in the field of nutritional research and asked these experts to address the various aspects of a claims substantiation process and the possibilities and limitations of the different approaches.

RESULTS

The experts spent a day presenting and discussing their views and arrived at several consensus statements that can serve as guidance for bodies performing claims assessments in the framework of regulatory systems.

CONCLUSION

The 26th Hohenheim Consensus Conference addresses some general aspects and describes the current scientific status from the point of view of six case studies to illustrate specific areas of scientific interest: carotenoids and vitamin A in relation to age-related macular degeneration, the quality of carbohydrates (as expressed by the glycemic index) in relation to health and well-being, probiotics in relation to intestinal and immune functions, micronutrient intake and maintenance of normal body functions, and food components with antioxidative properties and health benefits.

Adverse blood transfusion outcomes: establishing causation

The transfusion of allogeneic red blood cells (RBCs) and other blood components is ingrained in modern medical practice. The rationale for administering transfusions is based on key assumptions that efficacy is established and risks are acceptable and minimized. Despite the cliché that, "the blood supply is safer than ever," data about risks and lack of efficacy of RBC transfusions in several clinical settings have steadily accumulated. Frequentist statisticians and clinicians demand evidence from randomized clinical trials (RCTs); however, causation for the recognized serious hazards of allogeneic transfusion has never been established in this manner. On the other hand, the preponderance of evidence implicating RBC transfusions in adverse clinical outcomes related to immunomodulation and the storage lesion comes from observational studies, and a broad and critical analysis to evaluate causation is overdue. It is suggested in several circumstances that this cannot wait for the design, execution, and conduct of rigorous RCTs. We begin by examining the nature and definition of causation with relevant examples from transfusion medicine. Deductive deterministic methods may be applied to most of the well-accepted and understood serious hazards of transfusion, with modified Koch's postulates being fulfilled in most circumstances. On the other hand, when several possible interacting risk factors exist and RBC transfusions are associated with adverse clinical outcomes, establishing causation requires inferential probabilistic methodology. In the latter circumstances, the case for RBC transfusions being causal for adverse clinical outcomes can be strengthened by applying modified Bradford Hill criteria to the plethora of existing observational studies. This being the case, a greater precautionary approach to RBC transfusion is necessary and equipoise that justifying RCTs may become problematic.

Ecology and transmission of Buruli ulcer disease: a systematic review

Buruli ulcer is a neglected emerging disease that has recently been reported in some countries as the second most frequent mycobacterial disease in humans after tuberculosis. Cases have been reported from at least 32 countries in Africa (mainly west), Australia, Southeast Asia, China, Central and South America, and the Western Pacific. Large lesions often result in scarring, contractual deformities, amputations, and disabilities, and in Africa, most cases of the disease occur in children between the ages of 4-15 years. This environmental mycobacterium, Mycobacterium ulcerans, is found in communities associated with rivers, swamps, wetlands, and human-linked changes in the aquatic environment, particularly those created as a result of environmental disturbance such as deforestation, dam construction, and agriculture. Buruli ulcer disease is often referred to as the "mysterious disease" because the mode of transmission remains unclear, although several hypotheses have been proposed. The above review reveals that various routes of transmission may occur, varying amongst epidemiological setting and geographic region, and that there may be some role for living agents as reservoirs and as vectors of M. ulcerans, in particular aquatic insects, adult mosquitoes or other biting arthropods. We discuss traditional and non-traditional methods for indicting the roles of living agents as biologically significant reservoirs and/or vectors of pathogens, and suggest an intellectual framework for establishing criteria for transmission. The application of these criteria to the transmission of M. ulcerans presents a significant challenge.

Importance of pharmaceutical composition and evidence from clinical trials and pharmacological studies in determining effectiveness of chondroitin sulphate and other glycosaminoglycans: a critique

Objectives

Chondroitin sulphate (CS) has attracted much interest over the past two decades or so as a biological agent for use in the relief of pain and joint symptoms in osteoarthritis. Earlier clinical investigations produced variable, if encouraging results. This variability was partly due to limitations on the study designs and the lack of availability of standardized CS. Recently, high quality and fully standardized CS (Condrosulf) has become available and its effects have been studied in large-scale osteoarthritis trials, which are discussed here.

Key findings

There is now evidence for symptom - and structure-modifying (radio-logically-observed) effects. These studies show that CS (a) has slow onset of response and that relief of pain may not be like that of the direct analgesic actions of non-steroidal anti-inflammatory drugs (NSAIDs), (b) there are indications of reduced need for intake of analgesics (e.g. NSAIDs) in patients taking CS, and (c) quality of life and cost-benefits may be associated with use of CS. Safety evaluations show that the incidence of adverse reactions is low. Pharmacokinetic studies indicate that although oral absorption is relatively fast CS has moderate oral bioavailability (15–24%) and that depolymerised and degraded CS that is evident after absorption, together with CS itself, may take some time to accumulate in target joints. The pharmacodynamic actions of CS indicate that it has anti-inflammatory effects that include multiple actions involving reduction of catabolic reactions and enhanced anabolic (proteoglycan) synthetic reactions in cartilage and may block osteoclast activation in bone. Further studies are required to (a) establish the effects of depolymerised and degraded CS on degradation of cartilage and bone in vitro, and (b) MRI and other investigations of the effects in osteoarthritis of long-term CS treatment.

Summary

The findings from this review show there may be potential value of CS in reducing the dependence on intake of NSAIDs and analgesics in patients with osteoarthritis, while at the same time having favourable safety.

Causal assessment of awkward occupational postures and low back pain: results of a systematic review

BACKGROUND CONTEXT

Low back pain (LBP) is a prevalent and costly musculoskeletal disorder that often occurs in the working-age population. Although numerous physical activities have been implicated in its complex etiology, determining causation remains challenging and requires a methodologically rigorous approach.

PURPOSE

To conduct a systematic review of the scientific literature focused on establishing a causal relationship between awkward occupational postures and LBP.

STUDY DESIGN

Systematic review of the literature using MEDLINE, EMBASE, CINAHL, Cochrane Library, and Occupational Safety and Health database, gray literature, hand-searching occupational health journals, reference lists of included studies, and experts. Evaluation of methodological quality using a modified Newcastle-Ottawa Scale for observational studies. Summary levels of evidence for each of the Bradford Hill criteria for causality for each category of awkward occupational posture and type of LBP.

SAMPLE

Studies reporting an association between awkward occupational postures and LBP.

OUTCOME MEASURES

Numerical association between different levels of exposure to awkward occupational postures and the presence or severity of LBP.

METHODS

A systematic review was performed to identify, evaluate, and summarize the literature related to establishing a causal relationship, according to Bradford Hill criteria, between awkward occupational postures and LBP.

RESULTS

This search yielded 2,766 citations. Eight high-quality studies reported on awkward occupational postures and LBP. Three were case-control studies, one was cross-sectional, and four were prospective cohort studies. There was strong evidence for consistency of no association between awkward occupational postures and LBP, with only two studies demonstrating significant associations in most of their risk estimates compared with six studies reported mainly nonsignificant associations. Two studies assessed dose response, with one study demonstrating a nonsignificant dose-response trend. Three studies were able to assess temporality, but all demonstrated nonsignificant risk estimates. Biological plausibility was discussed by two studies. There was no available evidence to assess the experiment criterion for causality.

CONCLUSIONS

There was strong evidence from six high-quality studies that there was no association between awkward postures and LBP. Similarly, there was strong evidence from three high-quality studies that there was no temporal relationship. Moreover, subgroup analyses identified only a handful of studies that demonstrated only weak associations and no evidence for other aspects of causality in certain specific subcategories. It is therefore unlikely that awkward occupational postures are independently causative of LBP in the populations of workers studied.

Patient blood management - a new paradigm for transfusion medicine?

The saving of many lives in history has been duly credited to blood transfusions. What is frequently overlooked is the fact that, in light of a wealth of evidence as well as other management options, a therapy deemed suitable yesterday may no longer be the first choice today. Use of blood has not been based upon scientific evaluation of benefits, but mostly on anecdotal experience and a variety of factors are challenging current practice. Blood is a precious resource with an ever limiting supply due to the aging population. Costs have also continually increased due to advances (and complexities) in collection, testing, processing and administration of transfusion, which could make up 5% of the total health service budget. Risks of transfusions remain a major concern, with advances in blood screening and processing shifting the profile from infectious to non‐infectious risks. Most worrying though, is the accumulating literature demonstrating a strong (often dose‐dependent) association between transfusion and adverse outcomes. These include increased length of stay, postoperative infection, morbidity and mortality. To this end, a recent international consensus conference on transfusion outcomes (ICCTO) concluded that there was little evidence to corroborate that blood would improve patients’ outcomes in the vast majority of clinical scenarios in which transfusions are currently routinely considered; more appropriate clinical management options should be adopted and transfusion avoided wherever possible. On the other hand, there are patients for whom the perceived benefits of transfusion are likely to outweigh the potential risks. Consensus guidelines for blood component therapy have been developed to assist clinicians in identifying these patients and most of these guidelines have long advocated more conservative ‘triggers’ for transfusion. However, significant variation in practice and inappropriate transfusions are still prevalent. The ‘blood must always be good philosophy’ continues to permeate clinical practice. An alternative approach, however, is being adopted in an increasing number of centres. Experience in managing Jehovah’s Witness patients has shown that complex care without transfusion is possible and results are comparable with, if not better than those of transfused patients. These experiences and rising awareness of downsides of transfusion helped create what has become known as ‘patient blood management’. Principles of this approach include optimizing erythropoiesis, reducing surgical blood loss and harnessing the patient’s physiological tolerance of anaemia. Treatment is tailored to the individual patient, using a multidisciplinary team approach and employing a combination of modalities. Results have demonstrated reduction of transfusion, improved patient outcomes and patient satisfaction. Significant healthcare cost savings have also followed. Despite the success of patient blood management programmes and calls for practice change, the potential and actual harm to patients caused through inappropriate transfusion is still not sufficiently tangible for the public and many clinicians. This has to change. The medical, ethical, legal and economic evidence cannot be ignored. Patient blood management needs to be implemented as the standard of care for all patients.