3. Results:
3.1 Search findings A total of 2674 articles were identified with the database search using keywords as mentioned in methodology section. 1852 articles remained after duplication removal. Next, the articles were screened by title and abstract reading to select the relevant studies and 745 remained at this step. The short case series reporting less than 5 patients were further excluded. After full-text revision, 679 articles were excluded for reasons described in Plasma flow chart. Hence, 13 studies all published in English, with 631 participants were included for further evaluation [6-18]. We followed the PRISMA guidelines, and the study selection procedure was illustrated by the PRISMA flow diagram (Figure 1). Three studies were conducted in USA, two in Spain, two in China and one each in Egypt, India, Israel, Brazil, Italy and Japan [6-18]. Six hundred and thirty one (631) patients were recruited from studies published between 1996 - 2017.