In the absence of a gold standard, we assessed construct validity by comparing AMSTAR with OQAQ as well as two global assessments. Construct validity was shown by intraclass correlation coefficient (ICC); this statistic reflects the extent to which the results of AMSTAR converge with the results of other "criterion" instruments. The analysis revealed that the construct validity was excellent, that is, the AMSTAR is a reliable and valid tool. Given the extremely strict implementation of Cochrane systematic review, such reviews conducted with high methodological quality have been widely recognized [52] ; the AMSTAR revealed Cochrane systematic reviews have higher quality scores than non-Cochrane systematic reviews, that is, the AMSTAR has an ability to discriminate methodological quality, so it is sensitive when applying it to a sample of systematic reviews in diverse quality. The relationship between AMSTAR quality score and the number of pages can be explained by the fact that Cochrane reviews always have considerable amount of pages, these extreme outliers determined the direction and strength of the association.