Dealing with publication bias in translational stroke research

Translational Block in Stroke: A Constructive and "Out-of-the-Box" Reappraisal

Why can we still not translate preclinical research to clinical treatments for acute strokes? Despite > 1000 successful preclinical studies, drugs, and concepts for acute stroke, only two have reached clinical translation. This is the translational block. Yet, we continue to routinely model strokes using almost the same concepts we have used for over 30 years. Methodological improvements and criteria from the last decade have shed some light but have not solved the problem. In this conceptual analysis, we review the current status and reappraise it by thinking "out-of-the-box" and over the edges. As such, we query why other scientific fields have also faced the same translational failures, to find common denominators. In parallel, we query how migraine, multiple sclerosis, and hypothermia in hypoxic encephalopathy have achieved significant translation successes. Should we view ischemic stroke as a "chronic, relapsing, vascular" disease, then secondary prevention strategies are also a successful translation. Finally, based on the lessons learned, we propose how stroke should be modeled, and how preclinical and clinical scientists, editors, grant reviewers, and industry should reconsider their routine way of conducting research. Translational success for stroke treatments may eventually require a bold change with solutions that are outside of the box.

Leisure Time Physical Activity Reduces the Risk for Stroke in Adults: A Reanalysis of a Meta-Analysis Using the Inverse-Heterogeneity Model

Objective

Apply more robust and additional analyses to a previous meta-analysis that reported statistically significant associations between leisure time physical activity (LTPA) and stroke.

Methods

A reanalysis of a previous meta-analysis that included nine prospective cohort studies representing 269,594 men and women 25-84 years of age and in which the association between LTPA and incident stroke was examined. Follow-up periods ranged from 7.7 to 32.0 years. Relative risks (RR) from each study were pooled using the inverse-heterogeneity model. Heterogeneity was examined using the Q statistic, inconsistency using I², and small-study effects using Doi plots and the LFK index. Influence and cumulative meta-analysis were also conducted.

Results

Using low LTPA as the reference, moderate LTPA was associated with a statistically significant reduction in the risk for stroke in men (RR = 0.79, 95% CI = 0.65 to 0.95) and a trend in women (RR = 0.88, 95% CI = 0.78 to 1.0). High LTPA was associated with a statistically significant reduction in the risk for stroke in both men (RR = 0.72, 95% CI = 0.60 to 0.86) and women (RR = 0.78, 95% CI = 0.66 to 0.92). No statistically significant heterogeneity was observed and inconsistency was low. However, potential small-study effects were observed. With each study deleted once, results remained statistically significant. Cumulative meta-analysis demonstrated stability in results since at least 2005.

Conclusions

Leisure time physical activity is associated with a reduced risk of stroke in both men and women. However, the small-study effects observed suggest the possibility that results may be exaggerated.

Systematic Reviewers in Clinical Neurology Do Not Routinely Search Clinical Trials Registries

We examined the use of clinical trials registries in published systematic reviews and meta-analyses from clinical neurology. A review of publications between January 1, 2008 and December 31, 2014 from five neuroscience journals (Annals of Neurology, Brain, Lancet Neurology, Neurology, and The Neuroscientist) was performed to identify eligible systematic reviews. The systematic reviews comprising the final sample were independently appraised to determine if clinical trials registries had been included as part of the search process. Studies acknowledging the use of a trials registry were further examined to determine whether trial data had been incorporated into the analysis. The initial search yielded 194 studies, of which 78 systematic reviews met the selection criteria. Of those, five acknowledged the use of a specific clinical trials registry: four reviewed unpublished trial data and two incorporated unpublished trial data into their results. Based on our sample of systematic reviews, there was no increase in the use of trials registries in systematic review searches over time. Few systematic reviews published in clinical neurology journals included data from relevant clinical trials registries.

Dissemination bias in systematic reviews of animal research: a systematic review

BACKGROUND

Systematic reviews of preclinical studies, in vivo animal experiments in particular, can influence clinical research and thus even clinical care. Dissemination bias, selective dissemination of positive or significant results, is one of the major threats to validity in systematic reviews also in the realm of animal studies. We conducted a systematic review to determine the number of published systematic reviews of animal studies until present, to investigate their methodological features especially with respect to assessment of dissemination bias, and to investigate the citation of preclinical systematic reviews on clinical research.

METHODS

Eligible studies for this systematic review constitute systematic reviews that summarize in vivo animal experiments whose results could be interpreted as applicable to clinical care. We systematically searched Ovid Medline, Embase, ToxNet, and ScienceDirect from 1st January 2009 to 9th January 2013 for eligible systematic reviews without language restrictions. Furthermore we included articles from two previous systematic reviews by Peters et al. and Korevaar et al.

RESULTS

The literature search and screening process resulted in 512 included full text articles. We found an increasing number of published preclinical systematic reviews over time. The methodological quality of preclinical systematic reviews was low. The majority of preclinical systematic reviews did not assess methodological quality of the included studies (71%), nor did they assess heterogeneity (81%) or dissemination bias (87%). Statistics quantifying the importance of clinical research citing systematic reviews of animal studies showed that clinical studies referred to the preclinical research mainly to justify their study or a future study (76%).

DISCUSSION

Preclinical systematic reviews may have an influence on clinical research but their methodological quality frequently remains low. Therefore, systematic reviews of animal research should be critically appraised before translating them to a clinical context.

A call for transparent reporting to optimize the predictive value of preclinical research

The US National Institute of Neurological Disorders and Stroke convened major stakeholders in June 2012 to discuss how to improve the methodological reporting of animal studies in grant applications and publications. The main workshop recommendation is that at a minimum studies should report on sample-size estimation, whether and how animals were randomized, whether investigators were blind to the treatment, and the handling of data. We recognize that achieving a meaningful improvement in the quality of reporting will require a concerted effort by investigators, reviewers, funding agencies and journal editors. Requiring better reporting of animal studies will raise awareness of the importance of rigorous study design to accelerate scientific progress.

Hypothermia in Traumatic Brain Injury – A Literature Review

Traumatic brain injury is the leading cause of death in young people. Induced hypothermia has been used as a therapeutic intervention to improve outcome, based on results of animal studies. This article reviews the mechanisms of brain injury, the results of animal and human studies and the reasons that human studies do not always reflect the success seen in animal studies and why results may be ‘lost in translation’ to treatment of patients. It concludes by suggesting further areas of work to investigate the clinical use of therapeutic hypothermia.