FIG 3.
Risk of bias. Blue box with plus sign indicates a low risk of bias; red box with question mark indicates an unclear risk of bias; teal box with minus sign indicates a high risk of bias. N/A, not applicable.
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.