To what extent are surgery and invasive procedures effective beyond a placebo response? A systematic review with meta-analysis of randomised, sham controlled trials.

BMJ Open · 2015 · PMC4679929 · PMID 26656986

Europe PMC DOI

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0.0000

closest p · 0.0× alpha

0.0500

boldest claim

The sentences

highly significantp<0.00001actually significant

The overall effect of surgery compared to sham surgery was highly significant (SMD 0.34, 95% CI 0.20 to 0.49; p<0.00001), while heterogeneity was large (I 2 =67%, p<0.00001).

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marginally significantp=0.05actually significant

The SMD for surgery versus sham surgery was non-significant for pain-related conditions (n=15, SMD=0.13, p=0.08), marginally significant for studies on weight loss (n=10, SMD=0.52, p=0.05) and significant for gastroesophageal reflux disorder (GERD) studies (n=5, SMD=0.65, p<0.001) and for other conditions (n=8, SMD=0.44, p=0.004).

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