Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Flow chart of the study selection process. * Individual patient data was requested by e-mail to 25 corresponding authors and resulted in 18 non-responders, 3 responders but data not provided, and 4 authors provided data (of which 1 had overlapping data and not included).
