Author(s): Egger M, Davey Smith G, Schneider M, Minder C
Objective: Funnel plots (plots of effect estimates against sample size) may be useful to detect bias in meta-analyses that were later contradicted by large trials. We examined whether a simple test of asymmetry of funnel plots predicts discordance of results when meta-analyses are compared to large trials, and we assessed the prevalence of bias in published meta-analyses.
Design: Medline search to identify pairs consisting of a meta-analysis and a single large trial (concordance of results was assumed if effects were in the same direction and the meta-analytic estimate was within 30% of the trial); analysis of funnel plots from 37 meta-analyses identified from a hand search of four leading general medicine journals 1993-6 and 38 meta-analyses from the second 1996 issue of the Cochrane Database of Systematic Reviews.
Main outcome measure: Degree of funnel plot asymmetry as measured by the intercept from regression of standard normal deviates against precision.
Results: In the eight pairs of meta-analysis and large trial that were identified (five from cardiovascular medicine, one from diabetic medicine, one from geriatric medicine, one from perinatal medicine) there were four concordant and four discordant pairs. In all cases discordance was due to meta-analyses showing larger effects. Funnel plot asymmetry was present in three out of four discordant pairs but in none of concordant pairs. In 14 (38%) journal meta-analyses and 5 (13%) Cochrane reviews, funnel plot asymmetry indicated that there was bias.
Conclusions: A simple analysis of funnel plots provides a useful test for the likely presence of bias in meta-analyses, but as the capacity to detect bias will be limited when meta-analyses are based on a limited number of small trials the results from such analyses should be treated with considerable caution.
Referred From: https://www.ncbi.nlm.nih.gov/pubmed/9310563
Author(s): Kurman RJ, Norris HJ
Author(s): Lacey JV Jr, Ioffe OB, Ronnett BM, Rush BB, Richesson DA, et al.
Author(s): Reed SD, Newton KM, Clinton WL, Epplein M, Garcia R, et al.
Author(s): Kurman RJ, Shih IeM
Author(s): Lacey JV Jr, Sherman ME, Rush BB, Ronnett BM, Ioffe OB, et al.
Author(s): Ferenczy A
Author(s): Stein CJ, Colditz GA
Author(s): Reed SD, Newton KM, Garcia RL, Allison KH, Voigt LF, et al.
Author(s): Ricci E, Moroni S, Parazzini F, Surace M, Benzi G, et al.
Author(s): Bobrowska K, Kamiński P, Cyganek A, Pietrzak B, Jabiry-Zieniewicz Z, et al.
Author(s): Heller DS, Mosquera C, Goldsmith LT, Cracchiolo B
Author(s): Gregoriou O, Konidaris S, Vrachnis N, Bakalianou K, Salakos N, et al.
Author(s): DerSimonian R, Kacker R
Author(s): Higgins JP, Thompson SG, Deeks JJ, Altman DG
Author(s): Higgins JP, Thompson SG
Author(s): Epplein M, Reed SD, Voigt LF, Newton KM, Holt VL, et al.
Author(s): Cheung AP
Author(s): Viola AS, Gouveia D, Andrade L, Aldrighi JM, Viola CF, et al.
Author(s): Kreiger N, Marrett LD, Clarke EA, Hilditch S, Woolever CA
Author(s): Weir HK, Sloan M, Kreiger N
Author(s): Epplein M, Reed SD, Voigt LF, Newton KM, Holt VL, et al.
Author(s): Nagamani M, Urban RJ
Author(s): Al-Jarrah M, Matalka I, Aseri HA, Mohtaseb A, Smirnova IV, et al.
Author(s): Guh DP, Zhang W, Bansback N, Amarsi Z, Birmingham CL, et al.
Author(s): Tankó LB, Christiansen C
Author(s): Midgette AS, Baron JA
Author(s): Cramer DW, Barbieri RL, Muto MG, Kelly A, Brucks JP, et al.
Author(s): Willett W, Stampfer MJ, Bain C, Lipnick R, Speizer FE, et al.
Author(s): Gandini S, Botteri E, Iodice S, Boniol M, Lowenfels AB, et al.
Author(s): Botteri E, Iodice S, Bagnardi V, Raimondi S, Lowenfels AB, et al.
Author(s): Thune I, Furberg AS
Author(s): Schonfeld SJ, Hartge P, Pfeiffer RM, Freedman DM, Greenlee RT, et al.
Author(s): Benshushan A, Paltiel O, Rojansky N, Brzezinski A, Laufer N
Author(s): Parslov M, Lidegaard O, Klintorp S, Pedersen B, Jønsson L, et al.
Author(s): Kelsey JL, LiVolsi VA, Holford TR, Fischer DB, Mostow ED, et al.
Author(s): Elwood JM, Cole P, Rothman KJ, Kaplan SD
Author(s): Parazzini F, La Vecchia C, Moroni S, Chatenoud L, Ricci E