Data Sources
Using the search strategy in Appendix Table 1 (available
at www.annals.org), we searched Ovid MEDLINE for
articles published from 1950 to 2010, limited the results to
references from 2005 to 2010 in the search string, and
then downloaded the results for further inclusion or exclusion
determination. References before 2005 that met our
inclusion or exclusion criteria were identified from a 2007
technology assessment report that performed a comprehensive
literature search from 1966 through 2005 (6). We also
searched the Cochrane Central Register of Controlled Trials
and identified additional citations from reference lists of
relevant articles. The initial literature search was completed
in 2009 and updated in November 2010.