<p>*The basis for the <b>assumed risk</b> (e.g. the median control group risk across studies) is provided in footnotes. The <b>corresponding risk</b> (and its 95% confidence interval) is based on the assumed risk in the comparison group and the <b>relative effect</b> of the intervention (and its 95% CI). <b>CI:</b> Confidence interval; <b>RR:</b> Risk ratio.</p><p>GRADE Working Group grades of evidence. <b>High quality:</b> Further research is very unlikely to change our confidence in the estimate of effect. <b>Moderate quality:</b> Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. <b>Low quality:</b> Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. <b>Very low quality:</b> We are very uncertain about the estimate.</p>1<p>Although the PONV results demonstrated significant heterogeneity (<i>P</i> = 0.003, <i>I</i><sup>2</sup> = 56%), it was partly explained by the dose of dexamethasone. <sup>2</sup>Downgraded by not comparing higher dose with lower dose directly, but upgraded by the dose-response gradient. <sup>3</sup>Although there was significant heterogeneity (<i>P</i><0.00001, <i>I</i><sup>2</sup> = 94%), it was partly explained by the dose of dexamethasone. <sup>4</sup>Publication bias as <i>Pr</i>>|<i>z</i>| = 0.06.</p><p>PONV: post-operative nausea and vomiting; VAS: visual analogue scales.</p><p><b>Patient or population:</b> patients undergoing thyroidectomy. <b>Settings:</b> evidence from China, Japan, Korea, Italy, Switzerland, Norway, Portugal. <b>Intervention:</b> dexamethasone. <b>Comparison:</b> placebo.</p><p>GRADE evidence.</p
