title: Early studies reported extreme findings with large variability: a meta-epidemiologic study in the field of endocrinology.
abstract: OBJECTIVE
  To evaluate the presence of extreme findings and fluctuation in effect size in endocrinology.
  
  
  METHODS
  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 tau(2).
  
  
  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.
authors.affiliation: Robert D and Patricia E Kern Center for the Science of Health Care Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA; Division of Health Care Policy and Research, Department of Health Sciences Research, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA. Electronic address: Wang.Zhen@mayo.edu.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Robert D and Patricia E Kern Center for the Science of Health Care Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA; Division of Preventive Medicine, Department of Medicine, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Fares
authors.initials: F
authors.lastname: Alahdab
authors.affiliation: Robert D and Patricia E Kern Center for the Science of Health Care Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA; Division of Preventive Medicine, Department of Medicine, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Jehad
authors.initials: J
authors.lastname: Almasri
authors.affiliation: Robert D and Patricia E Kern Center for the Science of Health Care Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA; Division of Preventive Medicine, Department of Medicine, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Qusay
authors.initials: Q
authors.lastname: Haydour
authors.affiliation: Robert D and Patricia E Kern Center for the Science of Health Care Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA; Division of Preventive Medicine, Department of Medicine, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Khaled
authors.initials: K
authors.lastname: Mohammed
authors.affiliation: Robert D and Patricia E Kern Center for the Science of Health Care Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA; Division of Preventive Medicine, Department of Medicine, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Abd Moain
authors.initials: AM
authors.lastname: Abu Dabrh
authors.affiliation: Mayo Clinic Library, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Prokop
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Wedad
authors.initials: W
authors.lastname: Alfarkh
authors.affiliation: Knowledge and Evaluation Research Unit, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Sumaya
authors.initials: S
authors.lastname: Lakis
authors.affiliation: Knowledge and Evaluation Research Unit, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA; Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Department of Medicine, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Victor M
authors.initials: VM
authors.lastname: Montori
authors.affiliation: Robert D and Patricia E Kern Center for the Science of Health Care Delivery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA; Division of Preventive Medicine, Department of Medicine, Mayo Clinic, 200 1st Street SW, Rochester, MN 55902, USA.
authors.forename: Mohammad Hassan
authors.initials: MH
authors.lastname: Murad
mesh_terms: D004704:Endocrinology; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D008297:Male; D017594:Publication Bias; D012107:Research Design
keywords: Bias; Effect size; Meta-analysis; Proteus effect; Publication bias; Systematic review