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Evidence-Based Medicine current issue



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Practising evidence-based medicine (EBM): a descriptive analysis of medical students whole-task EBM assignments

2017-03-23T02:43:32-07:00

Researchers have suggested whole-task learning activities to practice and teach evidence-based medicine (EBM); however, limited description exists of their use in EBM curricula. This article describes medical students' execution of a whole-task EBM assignment and characterises themes emerging from assignment submissions. Between 2013 and 2015, Stanford University's paediatric clerkship students completed a whole-task EBM assignment based on a patient encounter. The assignment captured students' efforts to perform all EBM steps and describe their patient scenario and future knowledge needs strategies. Assignments were analysed using descriptive statistics and qualitative description. 123 students completed the assignment. Students formulated therapy (n=76), prognosis (n=18), diagnosis (n=15), harm (n=9) and aetiology (n=2) questions, and used a single (n=58) or multiple information resources (n=57). Based on evidence appraisal, 95 students indicated that the found evidence would inform future practice while 16 were sceptical of its conclusivity. 65 learners wanted to share evidence with colleagues; 33 with patients and families. To meet future knowledge needs, learners suggested using a structured approach (eg, PICO (patient, intervention, comparison and outcome); n=58), reading more primary literature (n=22) and creating question logs (n=21). This article provides a glimpse into students' EBM process and demonstrates the feasibility of whole-task activities for use in EBM training. Findings related to students’ clinical uncertainty and information sharing raise questions about coverage of these topics in current EBM training and suggest that further investigation is warranted.




Survey of instructions for authors on how to report an update of a systematic review: guidance is needed

2017-03-23T02:43:32-07:00

Systematic reviews have become the cornerstone of evidence-based healthcare. Approximately half of the systematic reviews are out of date after 5.5 years, and keeping them up to date remains a huge challenge. Despite new guidance on when and how to update systematic reviews, there seems to be a lack of guidance on how to report updates of systematic reviews. Therefore, we decided to systematically analyse instruction for authors in biomedical journals regarding guidance on reporting updates of systematic reviews. We conducted a survey investigating 250 journals. The journal list was derived by a twofold strategy. First, we chose a list of journals that were included in a recently published survey of systematic reviews. This list was augmented by a PubMed search for published updates of systematic reviews. For each journal, we checked the instructions for authors for any content or links related to updating systematic reviews in September 2016. Out of 250 journals, we found only one with guidance clearly related to updates of systematic reviews, namely the BioMed Central journal, Systematic Reviews. Nevertheless, concrete guidance on reporting is lacking as it is stated that authors are encouraged to be innovative in how to report and present systematic review updates. This makes clear that there remains a fundamental uncertainty of how authors willing to update a previously published systematic review should act as even the leading journal in evidence syntheses does not have clear guidance. Debate is necessary on how to report updates of systematic reviews.




The Maimed Martian, credible intervals and bias against benefit

2017-03-23T02:43:32-07:00

A sad little story about a maimed Martian astronaut is used to illustrate a method of improving confidence interval (CI) calculations. CIs in medical statistics are currently calculated from the data available in a clinical trial or meta-analysis considered in isolation from all other information available on earth. Likewise, the Martian in the story uses only information available to it, in isolation from further information from earth. However, there is further objective knowledge available to people on earth to improve the Martian's estimate. In the same way, we have objective prior knowledge available to us outside of the current clinical trial results which we can use to improve CI calculations. This prior knowledge is incorporated into the CI calculations using Bayesian methods. The objective prior knowledge that is available is the fact that there were researchers who felt it worthwhile to conduct the trial and journal editors who felt it worthwhile publishing the results. It is shown here that the use of this information contracts the width of the log CI by a factor of about three quarters on average. Unlike standard CIs, these new intervals also have the advantage of being directly interpretable in terms of probabilities. These probabilities also enable calculation of improved point estimates. These calculations are applied to 100 randomly selected Cochrane systematic reviews and show serious problems in assessing medical treatments. For treatments not involving new drugs or devices, it is shown that there is evidence of a bias towards a negative assessment. The calculations here make a quantitative adjustment for publication bias. They show that the proportion of negative assessments do not reflect an appropriate adjustment for publication bias.




Reflections on using non-inferiority randomised placebo controlled trials in assessing cardiovascular safety of new agents for treatment of type 2 diabetes

2017-03-23T02:43:33-07:00

The 2008 Food and Drug Administration (FDA) guidance to industry requires experimental evidence that new agents to treat type 2 diabetes do not have an unacceptable increase in cardiovascular risk. They specify this unacceptable increase to be a risk ratio of 1.3 in non-inferiority trials which may use placebo control. Clinically, this means that if a new agent achieves this threshold of not being 30% worse than placebo it is declared ‘non-inferior’. This guidance was in response to safety concerns raised about medications approved on their basis of reducing glycated haemoglobin alone. There was concern that this FDA guidance would stifle new drugs coming to market. On the contrary, there have been a number of exciting new classes of agents approved with improved confidence that they reduce glycated haemoglobin, and that they also do not excessively increase cardiovascular risk. Cardiovascular safety trials have been conducted for a number of novel medications using a non-inferiority approach. However, clinicians need to recognise that the results of non-inferiority trials are not as credible as superiority trials. It is important to closely review the trials before accepting claims of ‘non-inferiority’ or ‘cardiac neutrality’ especially when these studies are often compared with placebo, and may be accepting estimates of effect which span potentially clinically meaningful harm. There are compelling reasons to further investigate agents showing promise in non-inferiority trials with superiority trials, which include prespecified subgroups, and with sufficient power and duration to provide robust estimates of harms and benefits to inform clinical decision-making.




Semaglutide is non-inferior to placebo for cardiovascular outcomes in patients with type 2 diabetes

2017-03-23T02:43:33-07:00

Commentary on: Marso SP, Bain SC, Consoli A, et al.. Semaglutide and cardiovascular outcomes in patients with type 2 diabetes. NEJM 2016;375:1834–44.

Context

Semaglutide is a glucagon-like peptide 1 (GLP-1) analogue under development for the treatment of type 2 diabetes. It is molecularly related to liraglutide but has a longer half-life, requiring once weekly dosing. US Food and Drug Administration (FDA) regulatory guidance requires evidence that new therapies for type 2 diabetes are not associated with an unacceptable increase in cardiovascular risk.1 2 This is defined as evidence that compared with placebo the risk ratio estimate has an upper 95% CI of 1.3; the initial preapproval phase may target the 1.8 margin; however, if 1.3 is not achieved then a postmarketing randomised safety trial is required.1 2

Methods

This was an industry-sponsored, non-inferiority randomised controlled trial in...




In simulation modelling, there are multiple ways to effectively screen for colorectal cancer

2017-03-23T02:43:33-07:00

Commentary on: Knudsen AB, Zauber AG, Rutter CM, et al.. Estimation of Benefits, Burden, and Harms of Colorectal Cancer Screening Strategies: Modeling Study for the US Preventive Services Task Force. JAMA 2016;315(23):2595–609.

Context

Of the available colorectal cancer (CRC) screening tests, only flexible sigmoidoscopy and faecal occult blood tests have been evaluated with randomized controlled trials (RCTs). Colonoscopy and faecal immunochemical tests (FITs) are commonly used for CRC screening, but RCT evidence will not be available for at least a decade.

Methods

For its 2016 CRC screening recommendation, the US Preventive Services Task Force (USPSTF) commissioned the Cancer Intervention and Surveillance Modeling Network (CISNET) to analyse 8 screening tests, in 204 screening strategies in a hypothetical cohort of US 40-year-olds, using 3 different models. Each model simulated the adenoma–carcinoma sequence with and without screening and had been validated and calibrated in comparison with data from...




Having your cake and EATing it too: early timing of multiple allergen introduction does not increase the risk of developing food allergy in standard risk, breastfed infants

2017-03-23T02:43:33-07:00

Commentary on: Perkin MR, Logan K, Tseng A, et al.. EAT Study Team. Randomized trial of introduction of allergenic foods in breast-fed infants. N Engl J Med 2016;374:1733–43.

Context

Food allergy is a chronic public health problem affecting as many as 8–10% of children and has no present cure or treatment.1 Though delayed allergen introduction was formerly recommended that children with a family history of atopy, this strategy was later retracted given no evidence that this approach was of benefit.2 3 Recently, more data have emerged supporting a protective association between early allergen introduction and a reduced risk of developing food allergy in high-risk infants, but not in standard-risk children.4

Methods

To address this question, Perkin et al5 undertook the Enquiring About Tolerance (EAT) study. In this study, 1303 exclusively breastfed infants with no risk...




Decompressive craniectomy for severe traumatic brain injury reduces mortality but increases survival with severe disability

2017-03-23T02:43:33-07:00

Commentary on: Hutchinson PJ, Kolias AG, Timofeev IS, et al.. Trial of Decompressive Craniectomy for Traumatic Intracranial Hypertension. N Engl J Med 2016;375:1119–30.

Context

There is little doubt that decompressive craniectomy can reduce mortality in traumatic brain injury; this was clearly demonstrated by previous trials investigating the efficacy of decompressive hemicraniectomy following ischaemic stroke.1 However, surgical decompression will not reverse the effects of the pathology that precipitated the neurological crisis and the concern has always been that the reduction in mortality comes at the cost of an increase in the number of survivors with severe neurological disability. The results of a recent study investigating the use of this procedure in the context of severe traumatic brain injury has provided more evidence to inform the debate regarding these issues.

Methods

The RESCUEicp trial was an international, multicentre randomised controlled trial that compared last-tier secondary...




Single dose of prophylactic oral dextrose gel reduces neonatal hypoglycaemia

2017-03-23T02:43:33-07:00

Commentary on: Hegarty JE, Harding JE, Gamble GD, et al.. Prophylactic oral dextrose gel for newborn babies at risk of neonatal hypoglycaemia: a randomised controlled dose-finding trial (the Pre-hPOD Study). PLoS Med 2016;13:e1002155.

Context

Oral dextrose gel is a novel therapeutic option to manage asymptomatic neonatal hypoglycaemia. Previous studies1–3 have shown that the use of 40% buccal dextrose gel along with feeds reduces the need for intravenous dextrose therapy, promotes maternal infant bonding and reduces cost. The ease of administering the dextrose gel via the buccal mucosa2 and improvement in breastfeeding rates have made this a popular therapy for hypoglycaemia and is currently being implemented in nurseries across the world. The incidence of hypoglycaemia is almost 50% in neonates with risk factors, including maternal diabetes, maternal β blocker therapy, large or small for gestational age and late-preterm infants. Hegarty...




Nasal continuous positive airway pressure outperforms heated high-flow nasal cannula therapy as primary respiratory therapy in preterm infants

2017-03-23T02:43:33-07:00

Commentary on: Roberts CT, Owen LS, Manley BJ, et al.. Nasal high-flow therapy for primary respiratory support in preterm infants. N Engl J Med 2016;375:1142–51.

Context

High-flow nasal cannula (HFNC) therapy for preterm newborn infants has quickly gained popularity,1 despite few studies evaluating the underlying mechanisms and lack of high-quality studies evaluating its efficacy.2 Our recent systematic review and meta-analysis,3 and the Cochrane review4 suggested that HFNC therapy was comparable in efficacy to continuous positive airway pressure (CPAP) as a primary mode of support in preterm infants at birth, for respiratory distress syndrome (RDS) in preterm infants at birth and as an aid after extubation from mechanical ventilation or CPAP. However, data for only a limited number of infants born at <32 weeks' gestation were available when HFNC was used as a primary mode of support after birth.




Thalamotomy using MRI-guided focused ultrasound significantly improves contralateral symptoms and quality of life in essential tremor

2017-03-23T02:43:33-07:00

Commentary on: Elias WJ, Lipsman N, Ondo WG, et al.. A Randomized Trial of Focused Ultrasound Thalamotomy for Essential Tremor. N Engl J Med 2016;375:730–9.

Context

Propranolol and primidone significantly reduce tremor by around 60% in 50% of patients with essential tremor (ET). When medication is ineffective or causes intolerable side effects, neurosurgical intervention may be considered. Until recently, radiofrequency (RF) ablation or deep brain stimulation (DBS) of the ventralis intermedius (VIM) thalamic nucleus were the main surgical options. Gamma knife thalamotomy avoids a burrhole but delayed effects make intraoperative validation impossible.1 Recent technical advances have enabled transcranial delivery of high-intensity focused ultrasound to create a thalamotomy with MRI guidance and real-time monitoring. Previous uncontrolled studies suggested that this may be a safe and effective alternative for patients with ET.2

Methods

This randomised controlled trial examined the effect of unilateral focused...




Stress management training should be an integral component of cardiac rehabilitation

2017-03-23T02:43:33-07:00

Commentary on: Blumenthal JA, Sherwood A, Smith PJ, et al.. Enhancing cardiac rehabilitation with stress management training: a randomized, clinical efficacy trial. Circulation 2016;133:1341–50.

Context

There is mounting evidence that psychosocial risk factors, including stress, anxiety, depression and social isolation, impede recovery after acute cardiac events and are associated with increased morbidity and premature death.1 While cardiac rehabilitation (CR) is the standard care for patients after an acute event, and has been shown to improve survival,2 it does not routinely address psychosocial risks or assist patients in self-management of these factors. The present study investigated the impact of including stress management training (SMT) within CR, in terms of stress reduction in the short term and clinical events in the following 3 years.

Methods

Patients who presented for CR were randomised to either comprehensive CR or CR enhanced by SMT (CR+SMT). The 12-week...




General practices that reduce antibiotic prescribing for self-limiting respiratory tract infections by 10% can expect to see one extra patient with pneumonia each year and one peritonsillar abscess each decade

2017-03-23T02:43:33-07:00

Commentary on: Gulliford MC, Moore MV, Little P, et al.. Safety of reduced antibiotic prescribing for self-limiting respiratory tract infections in primary care: cohort study using electronic health records. BMJ 2016;354:i3410.

Context

Unnecessary antibiotic use in the community is a major driver for the development of resistant bacterial carriage.1 Despite the self-limiting nature of most acute respiratory tract infections (RTIs),2 a substantial proportion of consultations in the community result in an antibiotic prescription.3 Clinicians over-prescribe antibiotics partly because non-antibiotic management might result in more complications, and because more serious infections can initially present innocuously.4 This study explored whether the incidence of specific infective complications was higher in patients registered with general practices that prescribed fewer antibiotics for self-limiting RTIs.

Methods

This was a retrospective observational cohort study using routinely collected data from 2005 to 2014 in the...




CPAP did not reduce cardiovascular events in patients with coronary or cerebrovascular disease and moderate to severe obstructive sleep apnoea

2017-03-23T02:43:33-07:00

Commentary on: McEvoy RD, Antic NA, Heeley E, et al.. CPAP for prevention of cardiovascular events in obstructive sleep apnea. N Engl J Med 2016;375:919–31

Context

Cardiovascular disease (CVD) is a major health problem globally. Many of the traditionally recognised risk factors contributing to adverse outcomes in these patients are managed in secondary prevention models. Obstructive sleep apnoea (OSA), a common condition in such patients,1 has been largely neglected. The first-line treatment of OSA is nasal continuous positive airway pressure (CPAP) treatment, which reduces daytime sleepiness and improves quality of life.2 However, the majority of individuals with CVD and concomitant OSA do not report daytime sleepiness. Until recently, there was a lack of long-term prospective randomised controlled trials (RCTs) addressing whether CPAP should be prescribed to non-sleepy OSA patients in CVD cohorts, solely to reduce new cardiovascular events.

Methods

This trial...




Placing preterm infants on their side at birth does not increase 5 min SpO2

2017-03-23T02:43:33-07:00

Commentary on: Stenke E, Kieran EA, McCarthy LK, et al.. A randomised trial of placing infants on their back or left side after birth. Arch Dis Child Fetal Neonatal Ed 2016;101:F397–400.

Placing preterm infants on their side appears to improve oxygenation and breathing patterns after1 2 and at birth.3 Current neonatal guidelines do not recommend any particular position,4 but previous guidelines5 6 suggested that infants could either be placed on their back or their sides during resuscitation or stabilisation. Preterm infants have floppy airways that may exacerbate respiratory distress leading to the assumption in this randomised controlled trial (RCT) that placing preterm infants on their left side would increase aeration and oxygenation even if advanced respiratory care, including continuous positive airway pressure (CPAP) and intubation, were required.

Methods

The RCT was conducted...




SGLT2 inhibitor empagliflozin reduces renal outcomes and dampens the progressive reduction in glomerular filtration rate in patients with type 2 diabetes and antecedents of cardiovascular disease

2017-03-23T02:43:33-07:00

Commentary on: Wanner C, Inzucchi SE, Lachin JM, et al.. Empagliflozin and progression of kidney disease in type 2 diabetes. N Engl J Med 2016;375:323–34.

Context

Patients with type 2 diabetes (T2D) are exposed to a high risk of cardiovascular disease (CVD) and premature mortality. A multirisk approach has proven to reduce both major cardiovascular events and mortality.1 However, improved longevity may lead to a higher risk of developing other diabetic complications, among which chronic kidney disease represents a major burden.

Inhibitors of renal sodium-glucose cotransporters type 2 (SGLT2) are oral glucose-lowering agents that promote glucosuria and dampen glucotoxicity, but also reduce body weight, arterial blood pressure and hyperuricaemia.2 By reducing these risk factors, SGLT2 inhibitors offer promise to reduce cardiovascular and renal outcomes in patients with T2D.

Methods

EMPA-REG OUTCOME aimed at investigating the effects of empagliflozin, a selective SGLT2...




Pregabalin is effective in reducing fibromyalgia pain

2017-03-23T02:43:33-07:00

Commentary on: Derry S, Cording M, Wiffen PJ, et al.. Pregabalin for pain in fibromyalgia in adults. Cochrane Database Syst Rev 2016;9:CD011790.

Context

Anticonvulsants have been widely used in pain management for more than 50 years. Published neuropathic pain treatment guidelines have suggested their use, especially for neuropathic pain.1 The review by Derry et al focuses on the use of one such agent, pregabalin, in the treatment of fibromyalgia, an accepted and validated but heterogeneous condition in which diagnosis is made through history, physical examination and the exclusion of other diseases explaining the key symptoms.

Methods

This was a systematic review of randomised, double-blind trials lasting 8 weeks or longer comparing either pregabalin to placebo or an active treatment for the treatment of pain in fibromyalgia. The Cochrane Central Register of Controlled Trials, MEDLINE and EMBASE were search for randomised controlled trials from inception to...




High-dose sulphonylurea treatment in patients with renal impairment should be considered with caution

2017-03-23T02:43:33-07:00

Commentary on: van Dalem J, Brouwers MC, Stehouwer CD, et al.. Risk of hypoglycaemia in users of sulphonylureas compared with metformin in relation to renal function and sulphonylurea metabolite group: population based cohort study. BMJ 2016;354:i3625.

Context

Type 2 diabetes mellitus (T2DM) is one of the most serious health problems worldwide.1 Strict glycaemic control has been emphasised, and the number of patients with the risk of hypoglycaemia has increased.2 Hypoglycaemia is a serious side effect of treatment with sulphonylureas, which stimulate insulin secretion regardless of blood glucose level. It is more common in patients using long-acting sulphonylureas with renally excreted active metabolites.3 Therefore, an increasing number of patients with renal impairment may currently live with the risk of hypoglycaemia. However, the incidence of hypoglycaemia when treating with sulphonylureas in patients with impaired renal function has remained unclear.

Methods

This...




Patients with coronary heart disease and very low blood pressure are at increased risk of cardiovascular events

2017-03-23T02:43:33-07:00

Commentary on: Vidal-Petiot E, Ford I, Greenlaw N, et al.. Cardiovascular event rates and mortality according to achieved systolic and diastolic blood pressure in patients with stable coronary artery disease: an international cohort study. Lancet 2016;388:2142–52.

Context

Very large observational studies have provided evidence against a ‘J-shaped association’ between systolic blood pressure (SBP) or diastolic blood pressure (DBP) and risk of cardiovascular disease (CVD).1 The log-linear relationship observed in these studies indicates that, within the normal physiological BP range, there is no threshold below which associations change qualitatively. In order to mitigate the risk of confounding and reverse causality, these studies appropriately excluded people with known CVD. However, this selection has contributed to continued controversy over possible thresholds, particularly among those with established coronary heart disease (CHD); over 20 studies have reported conflicting findings on the existence of a threshold, its exact level and the...




Adverse events associated with mood stabiliser treatment should be continuously monitored in patients diagnosed with bipolar affective disorder

2017-03-23T02:43:33-07:00

Commentary on: Hayes JF, Marston L, Walters K, et al.. Adverse Renal, Endocrine, Hepatic, and Metabolic Events during Maintenance Mood Stabilizer Treatment for Bipolar Disorder: A Population-Based Cohort Study. PLoS Med 2016;13(8):e1002058.

Context

Bipolar disorder is most often severe and recurrent, requiring pharmacological maintenance treatment in combination with psychoeducation and/or other interventions.1 Evidence for the efficacy and tolerability of pharmacological treatment is primarily based on randomised controlled trials (RCTs). However, RCTs are usually characterised by a relatively short duration of follow-up and by relatively small sample sizes. Therefore, for detecting and evaluating rare and long-term side effects, large observational cohort studies have been conducted. Even though selection bias and confounding cannot be avoided in non-randomised studies, various approaches in terms of design and analysis are available for balancing the comparative groups and/or for confounder control, for example, case–control design, use of propensity score models or...




Both a stage shift and changes in stage-specific survival have contributed to reductions in breast cancer mortality

2017-03-23T02:43:33-07:00

Commentary on: Welch HG, Prorok PC, O'Malley AJ, et al.. Breast-cancer tumor size, overdiagnosis, and mammography screening effectiveness. N Engl J Med 2016;375:1438–47.

Context

Since randomised trials demonstrated a reduction in breast cancer mortality with mammographic screening, such screening has become widespread in developed countries, and mortality from breast cancer has declined in recent decades.1 There is interest in quantifying the proportion of this mortality reduction attributable to screening and that attributable to improvements in treatment.

Methods

This paper reported on analysis of breast cancer incidence and case death in women aged 40 years and over in the USA by tumour size. The authors compared prescreening results (1975–1979) with postscreening (2008–2012 for size distribution, 2000–2002 for 10-year case death). They used a similar approach to Duffy et al2 positing that reductions in death from a temporal shift to smaller tumours can be...




Passive leg raising may serve as the primary method to quickly assess fluid responsiveness in haemodynamically unstable patients

2017-03-23T02:43:33-07:00

Commentary on: Bentzer P, Griesdale DE, Boyd J, et al.. Will this hemodynamically unstable patient respond to a bolus of intravenous fluids? JAMA 2016;316:1298–309.

Context

Administration of intravenous fluids still serves as the cornerstone of haemodynamic resuscitation, yet both insufficient as well as overzealous fluid loading can increase morbidity and mortality. Correctly predicting fluid responsiveness is thus of the utmost importance, especially since only half of critically ill patients positively respond to a fluid bolus. Bentzer et al investigated the diagnostic performance of different methods in predicting fluid responsiveness.

Methods

Using MEDLINE and EMBASE, a total of 651 studies were identified investigating different methods to predict fluid responsiveness in haemodynamic unstable patients with refractory hypotension and/or signs of organ hypoperfusion. After exclusion of lower quality studies, trials with ≤20 patients and studies performed in elective cardiothoracic surgery patients, a systematic review and meta-analysis was performed...