FIGURE 1.
Flow chart of the literature search process according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.
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.