The OQAQ was selected as a criterion tool because it had been rigorously developed, its face validity was strong, and its validity had been thoroughly tested [6] . We assessed construct validity by comparing AMSTAR, OQAQ, and a self-developed global assessment scale. Construct validity was showed by intraclass correlation coefficient (ICC); for the purpose of calculating ICC, we adopted methods used by the AMSTAR group [8] , and converted the mean total scores (mean of two assessors) of per review to the percentage of maximum score (11 points in AMSTAR and 9 points in OQAQ accordingly); in addition, we developed a 100-point rating scale for overall quality assessment based on answers to the eleven questions in AMSTAR, in which two assessors indicated his or her judgments by checking tick-marks on a horizontal line (0 to 100 point), an SR without any flaws would be scored 100 points. Meanwhile, we also adopted the item 10 in OQAQ as a validated global assessment instrument. The overall mean scores (mean of two assessors), either using the self-developed 100point rating scale or using the item 10 from OQAQ, were also taken to verify the construct validity of AMSTAR. The feasibility of AMSTAR was assessed by recording the time it took to complete scoring, and paired t-test or nonparametric test was applied when comparing with OQAQ.