This paper has been prepared on the basis of available information of which the Foundation is aware from public literature and expert opinion and attempts to be current to the date of publication. [...] Most discrepancies reflected differences of opinion on the applicability of certain items to specific study designs and on the assignment of “yes” versus “partial” to the fulfillment of specific criteria. [...] Evaluation of the remaining studies included in the systematic review, including re-evaluation of the original sample of ten studies, is currently underway. [...] This threshold will be determined by considering both the distribution of the quality scores and the time and resource constraints of the project. [...] For example, Juni et al applied 25 different quality scales to 17 clinical trials comparing two types of heparin for the prevention of postoperative thrombosis and found that the type of scale used influenced the results of meta-analyses.21 Our checklists are admittedly subjective and reflect our perceptions of the key components of study quality, defined in terms of internal study validity.