Time to publication for results of clinical trials

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Abstract
It has been suggested that a time-lag bias exists whereby research studies with striking results are more likely to be stopped earlier than originally planned, published quicker, or both. If time-lag bias exists, new interventions might be mistakenly assumed to be effective. To study the extent to which time to publication of a clinical trial is influenced by the significance of its result. Studies were identified by searching the Cochrane Methodology Register (The Cochrane Library, Issue 3, 2005), MEDLINE (1966 to May 2005), EMBASE (1980 to May 2005), Science Citation Index (June 2005) and by handsearching journals and conference abstracts. Studies were eligible if they contained analyses of any aspect of the time to publication of clinical trials and tracked the publication of a cohort of clinical trials. Data extraction was performed independently by two authors. Data were extracted on the median time from the date the trial started to the date of publication. Data were also extracted on source of trials under investigation; source of funding; area of health care; means by which the publication status of these trials were sought; and methodological quality of the empirical study. Two studies with a total of 196 trials met the inclusion criteria. In both studies just over half of all trials had been published in full. Trials with positive results (i.e. statistically significant in favour of the experimental arm) were published in approximately 4 to 5 years. Trials with null or negative results (i.e. not statistically significant or statistically significant in favour of the control arm) were published after about 6 to 8 years. One study suggested that this difference could, in part, be attributed to the length of time taken to publish the results of a trial once follow up has been completed. This study showed that trials with null or negative findings took, on average, just over a year longer to be published than those with positive results. Our review shows that trials with positive results are published sooner than other trials. This has important implications for the timing of the initiation and updating of a review, especially if there is an association between the inclusion of a trial in a review and its publication status. It is of particular concern when one considers reviews containing only a small number of studies. 臨床試驗結果對出版研究成果所需時間的影響 有人說臨床研究有時間差的偏差(timelag bias)，因為結果比較醒目的研究，更可能提早結束、更早出版﹐或兩者皆是。如果有時間差的偏差，新療法可能會因此被誤認為有效。 研究臨床試驗結果的顯著性對出版研究成果所需時間的影響。 搜尋Cochrane Methodology Register (The Cochrane Library, Issue 3, 2005), MEDLINE (1966年到2005年5月), EMBASE (1980年到2005年5月), Science Citation Index (2005年6月)，並以人工搜尋雜誌及會議摘要。 凡是臨床試驗出版結果所需時間的相關研究均納入，並追蹤一群臨床試驗結果後續出版的狀況。 兩位作者各自獨力擷取資料。擷取的資料包括：從臨床實驗開始到結果出版所需時間的中位數，研究的臨床試驗的來源、經費來源、健康照顧領域、確認這些臨床試驗出版狀態的方法、以及該實證研究方法學的品質。 兩篇研究共含196個臨床試驗符合入選條件。兩篇研究中都只有一半臨床試驗有完整的報告。具正面結果的臨床試驗(指實驗組較佳達到顯著意義)大約在4到5年後出版。無結果或具負面結果的臨床試驗(指未達統計上顯著意義或對照組結果較佳達到顯著意義)大約在6到8年後出版。有一研究推測其間的差異﹐一部份原因是﹐在試驗完成後﹐出版結果所需要的時間不同所致，此研究顯示出版無結果或具負面結果的臨床試驗﹐比具正面結果的臨床試驗平均要多花一年的時間。 我們的回顧顯示具正面結果的臨床試驗比其他臨床試驗較快出版。這對於考慮開始或更新一篇回顧的時間點很重要，尤其是當是否納入某臨床試驗和其出版狀態有關時。特別是當一篇回顧只包含少數研究時。 本摘要由慈濟醫院葉日弌翻譯。 此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。 本篇方法學回顧的目標,在評估臨床試驗出版所需的時間是否受到其試驗結果的影響(時間差的偏差)。如果具正面結果的臨床試驗與無結果或具負面結果的臨床試驗相比﹐比較可能提早結束且比較快出版，那新的治療可能會因此被誤認為有效。兩篇研究共含196個臨床試驗符合入選條件。在兩篇研究中﹐都只有一半的臨床試驗後續有完整出版發表。具正面結果的臨床試驗(指實驗組較佳且達到顯著意義)大約在4到5年後出版。無結果或具負面結果的臨床試驗(指未達統計上顯著意義或對照組結果較佳達到顯著意義)大約在6到8年後出版。有一研究推測其間的差異﹐一部份原因是在試驗完成後到出版結果所需要的時間不同所致，此研究顯示出版無結果或具負面結果的臨床試驗比具正面結果的臨床試驗平均要多花一年。我們的回顧顯示﹐具正面結果的臨床試驗比其他臨床試驗較快出版。這對於考慮文獻回顧與更新回顧的時間點很重要，尤其當臨床試驗是否納入會受到出版狀態影響時。如果回顧所納入的研究為數不多時﹐影響將更為顯著。