• 1. Department of Population Medicine, College of Medicine, Qatar University, Doha, Qatar;
  • 2. Department of Clinical Research Management, West China Hospital, Sichuan University, Chengdu, 610041, P.R.China;
  • 3. Department of Pediatrics, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Alberta, Canada;
  • 4. West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, 610041, P.R.China;
  • 5. UQ Centre for Clinical Research, Faculty of Medicine, University of Queensland, Brisbane, Australia;
  • 6. Department of Statistics, Florida State University, Tallahassee, Florida, USA;
  • 7. Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, Lanzhou, 730000, P.R.China;
  • 8. Institute of Basic Research in Clinical Medicine, China Academy of Chinese Medical Sciences, Beijing, 100070, P.R.China;
  • 9. Department of Psychiatry, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Alberta, Canada;
XU Chang, Email: xuchang2016@runbox.com
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Objective Zero-events studies frequently occur in systematic reviews of adverse events, which consist of an important source of evidence. We aimed to examine how evidence of zero-events studies was utilized in the meta-analyses of systematic reviews of adverse events.Methods We conducted a survey of systematic reviews published in two periods: January 1, 2015 to January 1, 2020 and January 1, 2008, to April 25, 2011. Databases were searched for systematic reviews that conducted at least one meta-analysis of any healthcare intervention and used adverse events as the exclusive outcome. An adverse event was defined as any untoward medical occurrence in a patient or subject in healthcare practice. We summarized the frequency of occurrence of zero-events studies in eligible systematic reviews and how these studies were dealt with in the meta-analyses of these systematic reviews.Results We included 640 eligible systematic reviews. There were 406 (63.45%) systematic reviews involving zero-events studies in their meta-analyses, among which 389 (95.11%) involved single-arm-zero-events studies and 223 (54.93%) involved double-arm-zero-events studies. The majority (98.71%) of these systematic reviews incorporated single-arm-zero-events studies into the meta-analyses. On the other hand, the majority (76.23%) of them excluded double-arm-zero-events studies from the meta-analyses, of which the majority (87.06%) did not discuss the potential impact of excluding such studies. Systematic reviews published at present (2015-2020) tended to incorporate zero-events studies in meta-analyses than those published in the past (2008-2011), but the difference was not significant [proportion difference=–0.09, 95%CI (–0.21, 0.03), P=0.12].Conclusion Systematic review authors routinely treated studies with zero-events in both arms as "non-informative" carriers and excluded them from their reviews. Whether studies with no events are "informative" or not, largely depends on the methods and assumptions applied, thus sensitivity analyses using different methods should be considered in future meta-analyses.

Citation: XU Chang, ZHOU Xiaoqin, Zorzela Liliane, JU Ke, Furuya-Kanamori Luis, LIN Lifeng, LU Cuncun, Musa Omran A.H., Vohra Sunita. Utilization of the evidence from studies with no events in meta-analyses of adverse events: An empirical investigation (Chinese translation). Chinese Journal of Clinical Thoracic and Cardiovascular Surgery, 2021, 28(12): 1494-1502. doi: 10.7507/1007-4848.202105085 Copy

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