PRISMA Flowchart.

<p><i>From</i>: Moher D, Liberati A, Tetzlaff J, Altman DG, The PRISMA Group (2009). <i>P</i>referred <i>R</i>eporting <i>I</i>terns for <i>S</i>ystematic Reviews and <i>M</i>eta-<i>A</i>nalyses: The PRISMA Statement. PLoS Med 6(7): e1000097. doi:<a href="http://dx.doi.org/10.1371/journal.pmed1000097" target="_blank">10.1371/journal.pmed1000097</a> For more information, visit <a href="http://www.prisma-statement.org" target="_blank">www.prisma-statement.org</a>.</p>