Early studies reported extreme findings with large variability: A meta-epidemiologic study in the field of endocrinology

Zhen Wang, Fares Alahdab, Jehad Almasri, Qusay Haydour, Khaled Mohammed, Abd Moain Abu Dabrh, Larry J. Prokop, Wedad Alfarkh, Sumaya Lakis, Victor Manuel Montori, Mohammad H Murad

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Objectives: To evaluate the presence of extreme findings and fluctuation in effect size in endocrinology. Study Design and Settings: We systematically identified all meta-analyses published in 2014 in the field of endocrinology. Within each meta-analysis, the effect size of the primary binary outcome was compared across studies according to their order of publication. We pooled studies using the DerSimonian and Laird random-effects method. Heterogeneity was evaluated using the I 2 and tau2. Results: Twelve percent of the included 100 meta-analyses reported the largest effect size in the very first published study. The largest effect size occurred in the first 2 earliest studies in 31% of meta-analyses. When the effect size was the largest in the first published study, it was three times larger than the final pooled effect (ratio of rates, 3.26; 95% confidence interval: 1.80, 5.90). The largest heterogeneity measured by I 2 was observed in 18% of the included meta-analyses when combining the first 2 studies or 17% when combing the first 3 studies. Conclusions: In endocrinology, early studies reported extreme findings with large variability. This behavior of the evidence needs to be taken into account when used to formulate clinical policies.

Original languageEnglish (US)
JournalJournal of Clinical Epidemiology
StateAccepted/In press - 2016


  • Bias
  • Effect size
  • Meta-analysis
  • Proteus effect
  • Publication bias
  • Systematic review

ASJC Scopus subject areas

  • Epidemiology


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