Risk of bias assessment
To facilitate assessment of risk of bias amongst the included studies, tools tailored to each studies design were used from the NIH website (12 ). Based on each study’s performance at each of the examined domains, an overall verdict of “Good” quality would be given if more than two thirds of the signaling questions had a positive answer, a “Fair” quality if half to two thirds did so and “Poor” in case less than half did so. Studies were assessed once again independently by the authors and an ultimate consensus was reached for each one.