Publication bias in plastic and reconstructive surgery: a retrospective review on 128 abstracts presented to the Annual EURAPS Meeting

Discrepancies between Conference Abstracts and Published Manuscripts in Plastic Surgery Studies: A Retrospective Review

Background

Inconsistency in results and outcomes between presented abstracts and corresponding published articles can negatively affect clinical education and care. The objective of this study was to describe the frequency of clinically meaningful change in results and outcomes between abstracts presented at the American Association of Plastic Surgeons annual conference and the corresponding published articles, and to determine risk factors associated with discrepancies.

Methods

All abstracts delivered as oral presentations at the American Association of Plastic Surgeons conference (2006-2016) were reviewed. Results and outcomes were compared with those in corresponding articles. We defined clinically meaningful discrepancy as any change in the directionality of an outcome, or a quantitative change in results exceeding 10%.

Results

Four hundred eighty-six abstracts were identified. Of these, 63% (N = 305) advanced to publication. Of the published studies, 19% (N = 59) contained a discrepancy. In 85% of these (N = 50), discrepancies could not be explained by random variation. Changes in sample size were associated with heightened risk for a discrepancy (OR 10.38, 95% CI 5.16-20.86, P < 0.001). A decrease in sample size greater than 10% increased the likelihood of a discrepancy by 25-fold (OR 24.92, 95% CI 8.66-71.68, P < 0.001), whereas an increase in sample size greater than 10% increased the likelihood of a discrepancy by eight-fold (OR 8.36, CI 3.69-19.00, P < 0.001).

Conclusions

Most discrepancies between abstract and published article were not due to random statistical variation. To mitigate the possible impact of unreliable abstracts, we recommend abstracts be marked as preliminary, that authors indicate whether sample size is final at time of presentation, and that changes to previously reported results be indicated in final publications.

Is there a difference in venous thrombosis rate in free flap anastomoses based on coupler diameter? A systematic review. Does Size Really Matter?

Background

The adage is to use the largest anastomotic coupler device (coupler) size possible, since smaller an anastomosis might be more susceptible to thrombosis. It is unclear if this wisdom is supported by data. This study tests the hypothesis that there is no difference in the reported literature in thrombosis rate between different coupler sizes.

Methods

We searched PubMed, Embase, and the Cochrane Library. After screening 235 studies, we included 11 retrospective case-series. According to the criteria of Newcastle–Ottowa Scale, quality score ranged from 2 to 4 (out of 5) and funnel plots indicated publication bias. We included a total of 5930 coupled anastomoses. We calculated thrombosis rate per coupler diameter with exact confidence intervals (CIs). We regard non-overlapping CIs as a significant difference.

Results

Nine studies reported no difference in thrombosis rate based on coupler size. Two studies report a potentially greater thrombosis rates in smaller sizes: (1) 2.0 mm 27% (95% CI 17%–40%, 17/62 cases) vs. 3.0 mm 6.3% (95% CI 2.8%–12%, 8/126 cases) and (2) 1.5 mm 6.9% (95% CI 2.8%–14%, 7/101 cases) vs. 3.0 mm group 1.2% (95% CI 0.64%–2.1%, 13/1079).

Conclusion

There is some evidence that suggests that smaller coupler sizes are associated with greater thrombosis rate, but the current available evidence has limitations. Performing a second anastomosis, in case, the first anastomosis is performed with a coupler size of 1.0, 1.5, or even 2.0 mm, can potentially reduce this rate, however, this remains to be determined.

Evaluating the Landscape of Clinical Research in Neurosurgery

BACKGROUND

Many clinical trials and observational research never reach publication in peer-reviewed journals. Unpublished research results, including neutral study findings, hinder generation of new research questions, utilize healthcare resources without benefit, and may place patients at risk without benefit.

OBJECTIVE

To examine the publication of neurosurgery trials listed in ClinicalTrials.gov.

METHODS

Clinical neurosurgery research was identified by searching the registry and categorized by study type. Associated publications were identified on Pubmed.gov.

RESULTS

Among the 709 studies identified, spine (292, 41.2%) studies were most common, followed by tumor and cranial (each 114, 16.1%). Funding was predominantly private (482, 68.0%), followed by industry (135, 19.0%) and National Institutes of Health (9, 1.3%). A lower proportion of published studies (vs unpublished) received private funding in functional (33.3 vs 65.3%) and tumor (80.0 vs 68.7%). Only 104/464 (22.4%) studies had an associated publication. The mean time from listed study completion to first publication was 31.0 ± 27.5 mo. Most published studies had significant study differences between treatment arms (n = 72, 69.2%); studies with neutral findings were less likely to be published (n = 13, 12.5%). Surgical discipline (P = .1), funding source (P = .8), patient age (P = .4), planned enrollment (P = .1), phase of trial (P = .3), and study type (P = .2) did not affect publication rates. However, the interaction between study category and funding source significantly affected publication rate (P = .04, generalized linear model, R2 = 0.05). Publication timing (1-way analysis of variance, P = .5) and frequency (chi-square, P = .2) did not differ among disciplines.

CONCLUSION

Clinical trials and observational research in neurosurgery are often not published promptly, especially if results were nonsignificant or the trial had private funding.

Full publication of results initially presented in abstracts

BACKGROUND

Abstracts of presentations at scientific meetings are usually available only in conference proceedings. If subsequent full publication of results reported in these abstracts is based on the magnitude or direction of the results, publication bias may result. Publication bias creates problems for those conducting systematic reviews or relying on the published literature for evidence about health and social care.

OBJECTIVES

To systematically review reports of studies that have examined the proportion of meeting abstracts and other summaries that are subsequently published in full, the time between meeting presentation and full publication, and factors associated with full publication.

SEARCH METHODS

We searched MEDLINE, Embase, the Cochrane Library, Science Citation Index, reference lists, and author files. The most recent search was done in February 2016 for this substantial update to our earlier Cochrane Methodology Review (published in 2007).

SELECTION CRITERIA

We included reports of methodology research that examined the proportion of biomedical results initially presented as abstracts or in summary form that were subsequently published. Searches for full publications had to be at least two years after meeting presentation.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data and assessed risk of bias. We calculated the proportion of abstracts published in full using a random-effects model. Dichotomous variables were analyzed using risk ratio (RR), with multivariable models taking into account various characteristics of the reports. We assessed time to publication using Kaplan-Meier survival analyses.

MAIN RESULTS

Combining data from 425 reports (307,028 abstracts) resulted in an overall full publication proportion of 37.3% (95% confidence interval (CI), 35.3% to 39.3%) with varying lengths of follow-up. This is significantly lower than that found in our 2007 review (44.5%. 95% CI, 43.9% to 45.1%). Using a survival analyses to estimate the proportion of abstracts that would be published in full by 10 years produced proportions of 46.4% for all studies; 68.7% for randomized and controlled trials and 44.9% for other studies. Three hundred and fifty-three reports were at high risk of bias on one or more items, but only 32 reports were considered at high risk of bias overall.Forty-five reports (15,783 abstracts) with 'positive' results (defined as any 'significant' result) showed an association with full publication (RR = 1.31; 95% CI 1.23 to 1.40), as did 'positive' results defined as a result favoring the experimental treatment (RR =1.17; 95% CI 1.07 to 1.28) in 34 reports (8794 abstracts). Results emanating from randomized or controlled trials showed the same pattern for both definitions (RR = 1.21; 95% CI 1.10 to 1.32 (15 reports and 2616 abstracts) and RR = 1.17; 95% CI, 1.04 to 1.32 (13 reports and 2307 abstracts), respectively.Other factors associated with full publication include oral presentation (RR = 1.46; 95% CI 1.40 to 1.52; studied in 143 reports with 115,910 abstracts); acceptance for meeting presentation (RR = 1.65; 95% CI 1.48 to 1.85; 22 reports with 22,319 abstracts); randomized trial design (RR = 1.51; 95% CI 1.36 to 1.67; 47 reports with 28,928 abstracts); and basic research (RR = 0.78; 95% CI 0.74 to 0.82; 92 reports with 97,372 abstracts). Abstracts originating at an academic setting were associated with full publication (RR = 1.60; 95% CI 1.34 to 1.92; 34 reports with 16,913 abstracts), as were those considered to be of higher quality (RR = 1.46; 95% CI 1.23 to 1.73; 12 reports with 3364 abstracts), or having high impact (RR = 1.60; 95% CI 1.41 to 1.82; 11 reports with 6982 abstracts). Sensitivity analyses excluding reports that were abstracts themselves or classified as having a high risk of bias did not change these findings in any important way.In considering the reports of the methodology research that we included in this review, we found that reports published in English or from a native English-speaking country found significantly higher proportions of studies published in full, but that there was no association with year of report publication. The findings correspond to a proportion of abstracts published in full of 31.9% for all reports, 40.5% for reports in English, 42.9% for reports from native English-speaking countries, and 52.2% for both these covariates combined.

AUTHORS' CONCLUSIONS

More than half of results from abstracts, and almost a third of randomized trial results initially presented as abstracts fail to be published in full and this problem does not appear to be decreasing over time. Publication bias is present in that 'positive' results were more frequently published than 'not positive' results. Reports of methodology research written in English showed that a higher proportion of abstracts had been published in full, as did those from native English-speaking countries, suggesting that studies from non-native English-speaking countries may be underrepresented in the scientific literature. After the considerable work involved in adding in the more than 300 additional studies found by the February 2016 searches, we chose not to update the search again because additional searches are unlikely to change these overall conclusions in any important way.