Obstetrics and Gynaecology Department, University of Auckland, Level 12, Support Building, Auckland City Hospital, Park Road, Grafton, 1142 Auckland, New Zealand.
School of Women's and Children's Health, University of New South Wales, Level 1, Royal Hospital for Women, Barker Street, Sydney, Randwick, NSW 2031, Australia.
Hum Reprod. 2017 Aug 1;32(8):1658-1666. doi: 10.1093/humrep/dex236.
Does publication bias or non-publication exist in fertility trials presented as conference abstracts?
This study did not detect any publication bias; however, it did identify a high level of non-publication, with only 49% of abstracts reaching full-text publication four or more years after abstract presentation.
Systematic reviews of randomized controlled trials (RCTs) are the foundation of evidence based medicine. Non-publication or publication deficit refer to the failure to publish trial results. A publication bias exists when there is any tendency on the parts of the investigators or editors to fail to publish study results on the basis or strength of the study findings. Both present a serious problem for researchers, clinicians and policymakers alike, and ultimately impact on patient care.
STUDY DESIGN, SIZE, DURATION: A retrospective cohort study identified 337 fertility RCTs presented as conference abstracts between 2007 and 2010, as captured by an electronic search of the Cochrane Gynaecology and Fertility Database. After excluding ineligible trials and duplicates, 224 abstracts remained.
PARTICIPANTS/MATERIALS, SETTING, METHODS: A search for the full-text papers of each abstract was undertaken in Pubmed, MEDLINE, Embase, CINAHL and Google in May 2015 using a probabilistic approach. Trial authors were contacted to query the publication status of abstracts when no full-text was identified. The association between individual variables and the probability of publication, and time to publication, was assessed using logistic regression and Cox regression, respectively.
Of the 224 included abstracts, only 110 (49%; 95% CI: 42.6, 55.6) were found to be published as full-text articles. Publication bias was not identified in this cohort; studies with positive results had a similar probability of reaching full-text publication 52/113 (46%; 95% CI: 37.0, 55.3) as studies with non-positive (negative or null) results 58/111 (52%; 95% CI: 17.8, 33.9) (adjusted odds ratio (AOR): 1.02; 95% CI: 0.53, 1.97). Similarly, the time from abstract presentation to full-text publication was similar in studies with positive and non-positive results. Oral presentations were more likely to be published, and to be published sooner, than poster presentations (poster presentation AOR: 0.31; 95% CI: 0.15, 0.61 and adjusted hazard ratio (AHR): 0.57; 95% CI: 0.38, 0.86). Studies that were not registered were less likely to be published and to have delayed publication, than studies which were registered either prospectively or retrospectively (AOR: 0.14; 95% CI: 0.04, 0.44 and AHR: 0.43; 95% CI: 0.25, 0.72). Abstracts which were presented a longer time ago also had a higher probability of reaching full-text publication (P = 0.01).
LIMITATIONS, REASONS FOR CAUTION: Commencing with a cohort of RCTs from ethics committee registers may provide a better picture of the extent of non-publication and publication bias, as not all trials reach the stage of abstract presentation. It is also possible that the search did not identify all published trials, as some may have been published after the follow-up period.
This study did not identify any publication bias. However, only half of the abstracts in this cohort have been published as full-text articles, four or more years after their presentation at a conference. This is similar to publication rates reported previously for fertility trials, and is despite increasing awareness of the importance of publishing trial results, and subsequent requirements for all RCTs to be registered prior to trial initiation. A better understanding of the reasons for non-publication should assist in facilitating the prompt full-text publication of RCTs in the future.
STUDY FUNDING/COMPETING INTEREST(S): Funding provided from the University of Auckland. All authors declare they have no conflicts of interest in relation to this article.
Not applicable.
在作为会议摘要呈现的生育试验中是否存在发表偏倚或未发表的情况？
本研究未发现任何发表偏倚；然而，确实存在高水平的未发表情况，只有 49%的摘要在摘要发表四年或更长时间后达到全文发表。
随机对照试验（RCT）的系统评价是循证医学的基础。未发表或发表不足是指未能根据研究结果的强度发表试验结果。发表偏倚是指研究人员或编辑有任何不发表研究结果的倾向。这两者都对研究人员、临床医生和政策制定者构成了严重的问题，最终影响到患者的护理。
研究设计、大小和持续时间：一项回顾性队列研究在 Cochrane 妇科和生育数据库中通过电子搜索，确定了 2007 年至 2010 年间作为会议摘要呈现的 337 项生育 RCT。排除不合格试验和重复后，仍有 224 个摘要。
参与者/材料、设置、方法：2015 年 5 月，使用概率方法在 Pubmed、MEDLINE、Embase、CINAHL 和 Google 中搜索每个摘要的全文论文。当未找到全文时，联系试验作者查询摘要的发表情况。使用逻辑回归和 Cox 回归分别评估个体变量与发表概率和发表时间之间的关系。
在纳入的 224 个摘要中，只有 110 个（49%；95%CI：42.6，55.6）被发现作为全文文章发表。该队列中未发现发表偏倚；阳性结果的研究与非阳性（阴性或无效）结果的研究达到全文发表的可能性相似（52/113 [46%]，95%CI：37.0，55.3 与 58/111 [52%]，95%CI：17.8，33.9）（调整优势比（AOR）：1.02；95%CI：0.53，1.97）。同样，从摘要发表到全文发表的时间在阳性和非阳性结果的研究中也相似。口头报告比海报报告更有可能发表，并且发表时间更早（海报报告 AOR：0.31；95%CI：0.15，0.61 和调整危险比（AHR）：0.57；95%CI：0.38，0.86）。未注册的研究不太可能发表，并且发表时间也较晚，而注册前瞻性或回顾性的研究则更有可能发表（AOR：0.14；95%CI：0.04，0.44 和 AHR：0.43；95%CI：0.25，0.72）。发表时间较长的摘要也有更高的全文发表概率（P=0.01）。
局限性、谨慎的原因：从伦理委员会注册处开始的 RCT 队列可能提供未发表和发表偏倚程度的更好图景，因为并非所有试验都达到摘要呈现的阶段。也有可能搜索未发现所有已发表的试验，因为有些试验可能在随访期之后发表。
本研究未发现任何发表偏倚。然而，该队列中只有一半的摘要在会议摘要发表四年或更长时间后作为全文文章发表。这与之前报道的生育试验的发表率相似，尽管人们越来越意识到发表试验结果的重要性，以及随后要求所有 RCT 在试验开始前进行注册。更好地了解未发表的原因应有助于促进未来 RCT 的全文快速发表。
研究资金/利益冲突：奥克兰大学提供资金。所有作者均声明他们在与本文相关的问题上没有利益冲突。
不适用。
