Correcting the literature: Improvement trends seen in contents of retraction notices

Objective To analyse retraction notices from 2016 and compare their quality to the 2008 notices. Results From 146 retractions retrieved, only 123 were included, of which, a clear reason for retraction was available for 122 (99.2%) and no reason was given for one (0.8%). The main reasons for retraction were mistakes 26.0% (n = 32), fraud 26.0% (n = 32), plagiarism 20.3% (n = 25), and overlap 8.1% (n = 10). In 100 (81.3%) cases, a mention of retraction was available on the original paper, in 15 (12.2%) there was no mention of retraction, and 8 (6.5%) papers were deleted. Compared to the previous cohorts, management of retraction has improved because 99.2% provided a clear reason, and 81.3% of original articles were available with a mention of the retraction. Electronic supplementary material The online version of this article (10.1186/s13104-018-3576-2) contains supplementary material, which is available to authorized users.


Introduction
It has been proven than proportion of retraction in Pubmed has increased tenfold between 1980s and 2005-2009 [1]. When looking beyond Pubmed, retractions are also growing: According to the RetractionWatch database (under formation yet), as on 6 February 2018, there were 1203 retractions in 2015, 1355 in 2016, and 1137 in 2017 (http://retra ction datab ase.org).
There are several reasons for authors and/or editors to retract papers. According to studies, different classifications of retraction have been proposed. Over time, in the literature, the 2013 prediction of Smith, the then British Medical Journal editor, was achieved, with 'fraud' and 'error' cited as the two main reasons for retracting [2].
There is a need to correct the literature, and we applaud the Journal of the American Medical Association policy [3] since it uses retractions for pervasive errors and scientific or research misconduct [3]. In 2012, a detailed policy for retraction existed for 65% (n = 147) of the top scientific journals ranked by impact factor [4]. Too many journals err in not correcting the literature. The quality of retraction notices has been challenged since studies observed that 3-18% of notices had no clear reason for retraction [5]. The RetractionWatch website publishes comments daily on retraction and on poorly written retractions. Most of the retractions are unclear and/or too short. Moreover, retracted papers do not always follow good practices (for example, make a specific mention of the availability of the original paper).
We previously analysed 244 retractions notices published in 2008 [6]. Formal retraction notices could not be retrieved for 9 of them. Of the 235 retractions available (96%), the reason was not explicit in 21 articles (9%). The most cited reasons were mistakes (28%), plagiarism (20%), fraud (14%), and overlap (11%). The original paper or its location was mentioned in 233 retractions (95%). Of these, 22% were available with no mention of the retraction.
No study on retraction was published after 2010, and hence, there is lack of information on whether the quality of retraction notices has improved over time. Our objective was to analyse retraction notices from 2016 and compare them to the 2008 notices.

Methods
To allow comparisons, we used the same methodology and classification, which is explained below, as in our previous article [5]. We included all the complete For each retraction, we examined the reason for retraction and categorised it if available. Using the same search strategy, we retrieved a new kind of notice, which was applicable only to Elsevier's policy and was labelled 'Withdrawn' (https ://www.elsev ier.com/about /our-busin ess/polic ies/artic le-withd rawal ). These notices did not concern published papers, but were rather in-press articles, and they were therefore excluded.

BMC Research Notes
We also retrieved the country of affiliation of the first author and the mention of retraction on the original article. The two authors read all the notices and appraised them. When discrepancies were observed, consensus was obtained by a common reading. The main outcome measure was the availability of a clear reason for retraction.

Results
Of the total 146 retractions retrieved (complete list available in Additional file 1), 6 were excluded (1 indexation error, 3 retracting multiple articles, 1 retraction of a newsletter, and 1 temporary removal before publication). We discarded 16 'withdrawn' notices. One notice was not available. The final population consisted of 123 retractions.

Discussion
Compared to the previous cohorts, management of retraction has improved with 99.2% providing a clear reason and 81.3% of the original articles still available with a mention of the retraction.
We believe that management of retraction has improved with time. In 2008, we observed that 21/235 (9%) notices did not state the reason for retracting the paper. We used the same methods with the 2016 sample and observed that 0.8% of 123 notices mentioned no reasons for retraction. Before 2010, studies observed that 3-18% of notices showed no reason for retraction. Moreover, we found that mention of retraction was available on 81.3% of retracted articles, this is also an improvement compared to the 60% found in 2008.
Our PubMed literature search was exhaustive; it was conducted over a 4-month period and represents a good sample for 2016, which allows for comparison with our 2008 sample (244 notices retrieved).
The reasons for retraction in the samples of 2008 and 2016 were relatively similar. A slight difference was observed for the reason 'fraud' , which accounted for 14% of the retraction reasons in 2008 and 26% in 2016. We hypothesise that this difference is due to the high presence of image manipulation. Indeed, during the review process, the authors felt that image manipulations were often cited, and therefore a specific variable was created. However, since this variable was not specifically searched in 2008, we cannot be certain that the difference is only due to image manipulation.
The need to report better retraction persists, as reasons are sometimes difficult to classify. We proposed using a standard form, but this requires testing [7]. This form is sometimes used by small journal editors. Retractions that

Limitations
The study period was short (4 months), however it was sufficient to describe the trend in retractions.