And its effect on systematic review outcomes. Study.
The reliability of systematic reviews, in particular meta-analyses they contain, can be improved if more attention is paid to missing outcome data. The availability of [core outcome sets] for specific health conditions might help with this and the concept has support from the majority of Co-ordinating Editors in [Cochrane review groups].
I seem to be coming across a number of bias in SR papers recently, as well as - not coincidentally, I'm sure - discussions re: the need for better, more consistent reporting.
Kirkham JJ, Gargon E, Clarke M, Williamson PR. Can a core outcome set improve the quality of systematic reviews? -- a survey of the Co-ordinating Editors of Cochrane review group. Trials. 2013 Jan 22;14(1):21.