I recomend to read The Lancet Series on reducing waste in research in low-income

and middle-income countries (LMICs) and Chalmers I, Bracken MB, Djulbegovic B, et al. How to increase value and reduce waste when research priorities are set. Lancet 2014;383: 156–65. This authors encourage to read all systematic review of evidence available before project development.

Thank you for your recommendation. One of the weaknesses of systematic reviews and meta-analyzes, in addition to publication bias, is that they usually focus on a level of evidence, primarily randomized clinical trials, obviating other studies, such as quasi-experimental or observational studies, however may provide relevant information, that for this reason, is not taken into consideration.