Variability among studies should be investigated

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Abstract
EDITOR,—Matthias Egger and George Davey Smith explain how pooling of smaller studies can turn out to be misleading after the subsequent publication of larger trials and suggest that meta-analyses of small trials should now be distrusted, even if their combined effect reaches significance.1 Yet they also point out that evidence from megatrials will continue to be unavailable for most medical interventions, and hence meta-analyses of smaller trials remain the only …