Is publication bias present in gastroenterological research? An analysis of abstracts presented at an annual congress

Publication bias in studies on biologic therapy for children with inflammatory bowel disease

OBJECTIVE

The utilization of biologic drugs in children with inflammatory bowel disease (IBD) surged following the publications of positive results in randomized controlled trials and real-world studies. We aimed to explore the extent of publication bias associated with these findings.

METHODS

Two reviewers assessed all abstracts evaluating the efficacy or safety of biologics presented at the annual European Society for Pediatric Gastroenterology Hepatology and Nutrition and North American Society for Pediatric Gastroenterology conferences from 2015 to 2019. Abstracts were classified as "positive" or "negative." Time to publication was analyzed using Kaplan-Meier curve and groups were compared using the log-rank test. A Cox proportional model was utilized to determine the likelihood of publication.

RESULTS

Out of 209 included abstracts, only 130 (62%) were published as full manuscripts. The median time to publication was 2.8 years (interquartile range = 0-8.2). In the univariate Cox model, the likelihood of publication was four times higher for abstracts reporting positive results (hazard ratio = 4.4 [95% confidence interval, CI = 2.3-8.5]). The probabilities for publication at 1, 3, and 5 years after the conference were 32%, 59%, and 66% for abstracts with significantly positive results in favor of biologic treatment compared to 10%, 22%, and 25% for those with negative results (p < 0.001). In multivariable model, positive results (odds ratio = 6.4 [95% CI = 2.5-16.4]) were significant associated with publication rate.

CONCLUSION

Only 62% of abstracts presented in medical conferences regarding biologics in pediatric IBD are eventually published as full manuscripts, and those reporting positive results were more likely to be published and at an earlier time. Clinicians, guideline groups, and medical authorities dealing with drug approval, need to be aware of potential publication bias of published studies when employing evidence-based management strategies.

Time to Publication for Randomized Clinical Trials Presented as Abstracts at Three Gastroenterology and Hepatology Conferences in 2017

Background & Aims

Results of randomized clinical trials are often first presented as conference abstracts, but these abstracts may be difficult to find, and trial results included in the abstract may not be followed by subsequent journal publications. In a review of abstracts submitted to eight major medical and surgical conferences in 2017, we identified 237 abstracts reporting primary results of randomized clinical trials accepted for presentation at three major gastroenterology and hepatology conferences. The aims of this new analysis were to determine the publication rate for these abstracts and the proportion of publications that included trial registration numbers in the publication abstract.

Methods

Clinical trial registries, PubMed, Europe PMC, and Google Scholar were searched through November 1, 2021, for publications reporting trial results for the selected abstracts. Publications were reviewed to determine if they included a trial registration number and if the registration number was in the abstract.

Results

Publications were found for 157 abstracts (66%) within four years of the conference. Publications were found more frequently for the 194 abstracts reporting results of registered trials (144, 74%) than for the 43 abstracts reporting unregistered trials (13, 30%), but only 67% of these 144 publications included the registration number in the publication abstract. Ten unpublished trials had summary results posted on ClinicalTrials.gov.

Conclusions

Clinical trial results could be more accessible if all trials were registered, authors included registration numbers in both conference and journal abstracts, and journal editors required the inclusion of registration numbers in publication abstracts for registered clinical trials.

The Potential of Biomaterial-Based Approaches as Therapies for Ischemic Stroke: A Systematic Review and Meta-Analysis of Pre-clinical Studies

Background: In recent years pre-clinical stroke research has shown increased interest in the development of biomaterial-based therapies to promote tissue repair and functional recovery. Such strategies utilize biomaterials as structural support for tissue regeneration or as delivery vehicles for therapeutic agents. While a range of biomaterials have been tested in stroke models, currently no overview is available for evaluating the benefit of these approaches. We therefore performed a systematic review and meta-analysis of studies investigating the use of biomaterials for the treatment of stroke in experimental animal models. Methods: Studies were identified by searching electronic databases (PubMed, Web of Science) and reference lists of relevant review articles. Studies reporting lesion volume and/or neurological score were included. Standardized mean difference (SMD) and 95% confidence intervals were calculated using DerSimonian and Laird random effects. Study quality and risk of bias was assessed using the CAMARADES checklist. Publication bias was visualized by funnel plots followed by trim and fill analysis of missing publications. Results: A total of 66 publications were included in the systematic review, of which 44 (86 comparisons) were assessed in the meta-analysis. Overall, biomaterial-based interventions improved both lesion volume (SMD: -2.98, 95% CI: -3.48, -2.48) and neurological score (SMD: -2.3, 95% CI: -2.85, -1.76). The median score on the CAMARADES checklist was 5.5/10 (IQR 4.25-6). Funnel plots of lesion volume and neurological score data revealed pronounced asymmetry and publication bias. Additionally, trim and fill analysis estimated 19 "missing" studies for the lesion volume outcome adjusting the effect size to -1.91 (95% CI: -2.44, -1.38). Conclusions: Biomaterials including scaffolds and particles exerted a positive effect on histological and neurological outcomes in pre-clinical stroke models. However, heterogeneity in the field, publication bias and study quality scores which may be another source of bias call for standardization of outcome measures and improved study reporting.