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BMJ Evidence-Based Medicine recent issues



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Overdiagnosis: what it is and what it isnt

2018-01-24T09:55:27-08:00

Why then, can one desire too much of a good thing?

William Shakespeare, As You Like It (1600)

Rosalind’s question, as she is about to marry Orlando, is purely rhetorical—she thinks that one cannot desire too much of a good thing. Nevertheless, trite though it may be, it is true that one can sometimes have it. It is certainly true of healthcare and has been referred to as ‘too much medicine’,1 although because of potential confusion with ‘too much medication’ a better term might be ‘too much healthcare’. This includes too much screening of asymptomatic individuals, too much investigation of those with symptoms, too much reliance on biomarkers, too many quasi-diseases, too much diagnosis, often leading to too much treatment, sometimes cost-ineffective, medicines that are too costly and too rapidly approved for marketing, too many adverse reactions, and too much inappropriate monitoring. And too much healthcare...




Beliefs, critical thinking and evidence-based medicine

2018-01-24T09:55:27-08:00

The field of evidence-based medicine (EBM) has evolved tremendously since the term was coined 25 years ago. There are improved tools for use in daily practice, helping clinicians and patients make informed decisions about treatment choices. The recently published ‘Evidence based medicine manifesto for better healthcare’,1 devised by the BMJ and the University of Oxford’s Centre for Evidence Based Medicine, has been read with great interest. Nonetheless, one can’t help but wonder: even when using the most up-to-date resources, how informed and unbiased are our clinical decisions, when we are subconsciously governed by our underlying beliefs, shaped by past experiences?

As humans, we carry perceptions that affect our daily decisions and actions. Studies in cognitive sciences have shown that our subconscious mind is constantly seeking evidence to support our pre-existing ideas, while any information challenging these notions is approached with psychological discomfort, scepticism and an unconscious drive to...




Rare adverse events in clinical trials: understanding the rule of three

2018-01-24T09:55:27-08:00

Investigators should report rare and very rare adverse events in clinical trials. Even though they may not give a signal in any single trial, a meta-analysis could reveal potentially important drug–adverse event associations that might require further verification. Data from a meta-analysis of such rare events can shorten the time to decision-making by regulatory agencies and/or drug manufacturers, especially in cases where the reported harms are severe.

The benefit-harm profiles of new medicines are usually not fully known at the time of regulatory approval. This is because most trials are powered to detect benefits but not adverse events and also because adverse events are selectively reported1 or misinterpreted.2

One issue is that the number of trial subjects required in a trial to have a 95% chance of detecting an adverse drug reaction at low frequencies is large (table 1). If a new medication caused...




Analysis of conference abstract-to-publication rate in UK orthopaedic research

2018-01-24T09:55:27-08:00

Presentation of research at orthopaedic conferences is an important component for surgical evidence-based practice. However, there remains uncertainty as to how many conference abstracts proceed to achieve full-text publication (FTP) for wider dissemination. This study aimed to determine the abstract-to-publication rate (APR) of research presented in the largest hip and knee orthopaedic meetings in the UK, and to identify predictive factors which influence the APR. All published abstracts (n=744) from the 2006, 2008, 2009 and 2010 British Hip Society (BHS) and the 2007, 2009, 2010 and 2011 British Association for Surgery of the Knee (BASK) annual conference meetings were examined by four researchers independently. To determine whether abstracts had been published in full-text form, Google Scholar, Medline and EMBASE evidence databases were used to verify FTP status. Variables including sample size, statistical significance, grade of the first author, research affiliated institution and research design were extracted and analysed to identify whether these were associated with FTP. 176 out of 744 abstracts achieved FTP status (APR: 23.7%). Factors associated with FTP status included statistically significant results (P<0.01) and research design (P=0.02). Factors not associated included sample size, grade of the first author and research affiliated institution (P>0.05). APRs of the assessed BHS and BASK annual conference presentations are low in comparison to other scientific meetings. Encouragement should be provided to clinicians and academics to submit their work for publication to address this short fall, thereby enhancing the potential for full-text research publications to inform evidence-based orthopaedics.




Interactive visualisation for interpreting diagnostic test accuracy study results

2018-01-24T09:55:27-08:00

Information about the performance of diagnostic tests is typically presented in the form of measures of test accuracy such as sensitivity and specificity. These measures may be difficult to translate directly into decisions about patient treatment, for which information presented in the form of probabilities of disease after a positive or a negative test result may be more useful. These probabilities depend on the prevalence of the disease, which is likely to vary between populations. This article aims to clarify the relationship between pre-test (prevalence) and post-test probabilities of disease, and presents two free, online interactive tools to illustrate this relationship. These tools allow probabilities of disease to be compared with decision thresholds above and below which different treatment decisions may be indicated. They are intended to help those involved in communicating information about diagnostic test performance and are likely to be of benefit when teaching these concepts. A substantive example is presented using C reactive protein as a diagnostic marker for bacterial infection in the older adult population. The tools may also be useful for manufacturers of clinical tests in planning product development, for authors of test evaluation studies to improve reporting and for users of test evaluations to facilitate interpretation and application of the results.




External validity, generalisability, applicability and directness: a brief primer

2018-01-24T09:55:27-08:00

External validity is a construct that attempts to answer the question of whether we can use the results of a study in patients other than those enrolled in the study. External validity consists of two unique underlying concepts, generalisability and applicability. When the concern is about extending the results from a sample to the population from which the sample was drawn, the problem is one of generalisability. When the concern is about using inferences drawn from study participants in the care of specific patients belonging to any population, the problem is one of applicability. Clinicians, guideline developers and policymakers do not struggle with generalisability, but often struggle with applicability. When applicability is deemed to be low for a certain population, certainty in the supporting evidence becomes low due to indirectness.




Catalogue of bias: allocation bias

2018-01-24T09:55:27-08:00

This article is part of a series of articles featuring the Catalogue of Bias introduced in this volume of BMJ Evidence-Based Medicine that describes allocation bias and outlines its potential impact on research studies and the preventive steps to minimise its risk. Allocation bias is a type of selection bias and is relevant to clinical trials of interventions. Knowledge of interventions prior to group allocation can result in systematic differences in important characteristics that could influence study findings. Allocation bias can overestimate effect size by up to 30%–40%. Sequentially numbered, opaque, sealed envelopes; containers; pharmacy-controlled randomisation and central computer randomisation are methods to minimise allocation bias.




Catalogue of bias: attrition bias

2018-01-24T09:55:27-08:00

This article is part of a series of articles featuring the Catalogue of Bias introduced in this volume of BMJ Evidence-Based Medicine that describes attrition bias and outlines its potential impact on research studies and the preventive steps to minimise its risk. Attrition bias is a type of selection bias due to systematic differences between study groups in the number and the way participants are lost from a study. Differences between people who leave a study and those who continue, particularly between study groups, can be the reason for any observed effect and not the intervention itself. Associations for mortality in trials of tranexamic acid and upper gastrointestinal bleeding were no longer apparent after studies with high or unclear risk of attrition bias were removed. Over-recruitment can help prevent important attrition bias. Sampling weights and tailored replenishment samples can help to compensate for the effects of attrition bias when present.




Catalogue of bias: observer bias

2018-01-24T09:55:27-08:00

This article is part of a series featured from the Catalogue of Bias introduced in this volume of BMJ Evidence-Based Medicine that describes biases and outlines their potential impact in research studies. Observer bias is systematic discrepancy from the truth during the process of observing and recording information for a study. Many healthcare observations are at risk of this bias. Evidence shows that treatment effect estimates can be exaggerated by a third to two-thirds in the presence of observer bias in outcome assessment. Preventing observer bias involves proper masking in intervention studies including the use of matched placebo interventions where appropriate and training of observers to make assessment consistent and reduce biases resulting from conscious or unconscious prejudices. Where observers are involved in a research study, it is probably not possible for the study to be entirely free of observer biases.




Correction: Ten essential papers for the practice of evidence-based medicine

2018-01-24T09:55:27-08:00

Nunan D, Sullivan JO, Heneghan C, et al. Ten essential papers for the practice of evidence-based medicine. Evidence-Based Medicine 2017;22:202–204.

When this article was first published in print, the title, subheadings and DOI number were missing due to a typesetting error. The online version was not affected by this (http://dx.doi.org/10.1136/ebmed-2017-110854). The article can be found in full on the following pages: 26-28.




Key Concepts for Informed Health Choices: a framework for helping people learn how to assess treatment claims and make informed choices

2018-01-24T09:55:27-08:00

Many claims about the effects of treatments, though well intentioned, are wrong. Indeed, they are sometimes deliberately misleading to serve interests other than the well-being of patients and the public. People need to know how to spot unreliable treatment claims so that they can protect themselves and others from harm. The ability to assess the trustworthiness of treatment claims is often lacking. Acquiring this ability depends on being familiar with, and correctly applying, some key concepts, for example, that’ association is not the same as causation.’ The Informed Health Choices (IHC) Project has identified 36 such concepts and shown that people can be taught to use them in decision making. A randomised trial in Uganda, for example, showed that primary school children with poor reading skills could be taught to apply 12 of the IHC Key Concepts. The list of IHC Key Concepts has proven to be effective in providing a framework for developing and evaluating IHC resources to help children to think critically about treatment claims. The list also provides a framework for retrieving, coding and organising other teaching and learning materials for learners of any age. It should help teachers, researchers, clinicians, and patients to structure critical thinking about the trustworthiness of claims about treatment effects.




When is a guideline not a guideline? The devil is in the details

2018-01-24T09:55:27-08:00

Introduction

Clinical practice guidelines (CPGs) are intended to enhance the practice of evidence-based medicine by streamlining healthcare delivery and improving the process and outcomes of patient care. Because guidelines are believed to represent the best evidence and best judgements, they are adopted as standards of care by payers and have a powerful influence on medical practice. However, because guideline development, like all areas of medicine, is vulnerable to biased judgements,1–3 commercial sponsorship of guidelines and conflicts of interest (COI) of panel members remains an important public health issue. There also are increasing concerns that common medical practices, often codified in CPGs, are not evidence based and may be drivers of overtreatment, raising questions about the quality and trustworthiness of guidelines.4–9

Certainly, some progress has been made in the last few years...




High incidence of cervical cancer in women over 60 is likely due to less intensive cervical screening in this generation of women

2018-01-24T09:55:27-08:00

Commentary on: Wang J, Andrae B, Sundstrom K, et al. Effectiveness of cervical screening after age 60 years according to screening history: nationwide cohort study in Sweden. PLoS Med 2017;14:e1002414.

Context

In many countries the distribution of the incidence of cervical cancer peaks at around 45 and 65 years of age. The reason for this phenomenon could have at least two explanations: (1) an underlying biological explanation so that the older a woman is the higher the risk for her to get cervical cancer no matter her vita sexualis or if she has participated in cervical screening, which is the case with, for example, breast and colorectal cancer; (2) women older than 60 years have participated less in cervical screening compared with younger women because the best available evidence demonstrates that cervical screening can have a primary preventive effect.1

Methods

In this cohort study,2 the Total Population...




Trial supports targeted radiotherapy for early breast cancer but protocol still requires 3 weeks of daily therapy

2018-01-24T09:55:27-08:00

Commentary on: Coles CE, Griffin CL, Kirby AM, et al. IMPORT Trialists. Partial-breast radiotherapy after breast conservation surgery for patients with early breast cancer (UK IMPORT LOW trial): 5-year results from a multicentre, randomised, controlled, phase 3, non-inferiority trial. Lancet 2017;390:1048–60.

Context

The evidence-based local treatment for early breast cancer is breast-conserving surgery and radiotherapy, requiring 3–6 weeks of daily whole breast external beam radiation therapy, which is inconvenient for patients and expensive.

The suggestion that targeted radiation to the tumour bed with modern techniques may be adequate was proposed in 1995.1 This was heralded as a new standard2 with the publication of the TARGIT-A trial3 4 of single-dose targeted intraoperative radiotherapy (TARGIT-IORT), later confirmed by other European studies using brachytherapy5 that requires 5 days of inpatient stay or EBRT.6

Methods

In this study,7 in 30 UK...




Low-dose levothyroxine did not improve symptoms in asymptomatic older people with subclinical hypothyroidism

2018-01-24T09:55:27-08:00

Commentary on: Stott DJ, Rodondi N, Kearney PM, et al. Thyroid hormone therapy for older adults with subclinical hypothyroidism. N Engl J Med 2017;376:2534–44.

Context

Subclinical hypothyroidism (SCH), defined as an elevated serum thyroid-stimulating hormone (TSH) with normal circulating free thyroid hormones, is a common and frequently asymptomatic condition. SCH becomes increasingly prevalent with advancing age,1 and current guidelines recommend no treatment for older patients with serum TSH concentrations between the upper limit of the reference range and 10 mU/L.2 However, as numerous large epidemiological studies show an excess of cardiovascular events and/or increased mortality in patients with SCH,3 there are important questions about whether long-term levothyroxine treatment could either ameliorate vascular risk in this population or improve symptoms of hypothyroidism.

Methods

In this study,4 737 individuals over the age of 65 years were recruited by screening laboratory and primary...




NSAIDs are superior to paracetamol for osteoarthritic pain and function in a network meta-analysis

2018-01-24T09:55:27-08:00

Commentary on: da Costa BR, Reichenbach S, Keller N, et al. Effectiveness of non-steroidal anti-inflammatory drugs for the treatment of pain in knee and hip osteoarthritis: a network meta-analysis. Lancet 2017;390:e21–33.

Context

Treatment of osteoarthritis includes analgesics, exercise, lifestyle changes, weight loss and other adaptations. Analgesics are often recommended and used together with exercise therapy. Recent studies and reviews support the use of exercise therapy as the first choice of treatment for osteoarthritis, followed by non-steroidal anti-inflammatory drugs (NSAIDs) and other modalities.1–4 However, several NSAIDs are available, and the preferred NSAID and dose for osteoarthritis are different between the available studies and recommendations.

Methods

This was a network meta-analysis of randomised controlled trials (RCTs) of different doses of NSAIDs or paracetamol for hip or knee osteoarthritis.5 The primary outcome was pain and the secondary outcome was physical function. The review...




Angiotensin II increases blood pressure in patients with refractory vasodilatory shock

2018-01-24T09:55:27-08:00

Commentary on: Khanna A, English SW, Wang XS, et al. ATHOS-3 Investigators. Angiotensin II for the treatment of vasodilatory shock. N Engl J Med 2017;377:419–430.

Context

Vasodilatory or distributive shock is the most common cause of shock in intensive care units (ICUs) and is characterised by low blood pressure due to peripheral vasodilation and relative hypovolaemia despite normal or increased cardiac output.1 Immediate treatment with fluids and vasopressors is required to ensure adequate organ perfusion. In several cases the desired level of mean arterial pressure (MAP) cannot be maintained despite high doses of conventional vasopressors, namely catecholamines.2 This condition is called refractory shock and is associated with a poor outcome.2 3 Several studies have investigated the effects of alternative vasopressors for treatment of vasodilatory shock.4 5 Angiotensin II was suggested as potential catecholamine-sparing agent for the treatment of...




Effect size in CANTOS trial

2018-01-24T09:55:27-08:00

The primary endpoint in Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) trial published by Ridker et al1 was non-fatal myocardial infarction, non-fatal stroke or cardiovascular death. The authors concluded that canakinumab 150 mg reduced primary event rates compared with placebo (3.86 vs 4.11 per 100 person-years) with HR 0.85 (95%CI 0.74 to 0.98; P=0.021). Sample size calculated assumed the difference in primary event rate of 20% between two groups, which they considered clinically relevant. We have argued previously that in order to call a trial superior, the 95% CI should lie outside this clinically relevant difference.2 In this study, the difference in the primary outcome is 15%, which is beyond the clinically relevant difference. Also, the 95% CI does not lie outside this difference; in fact, the upper margin is close to 1(figure 1a).

Such interpretation of superiority trials borrows from the concept of non-inferiority margin used in non-inferiority...