“…We assessed the internal validity of each study using the following criteria (see the appendix) (24,26): (i) adequate randomization of allocation, (ii) blinding of study participants for treatment, (iii) comparability, or adjustment for incomparability, of the base-line characteristics3 supposedly of relevance to prognosis (27)(28)(29)(30)(31)(32)(33), (iv) loss to follow-up of less than 20%, and (v) intention-to-treat analysis.…”