2.3. Data Extraction and Analysis

Four researchers (P.A.-C., A.T.-G., M.C.R.-M., D.R.-A.) carried out the bibliographic searches, and two reviewers (A.T.-G. and D.R.-A.) subsequently reviewed the relevance of the titles and abstracts according to the inclusion and exclusion criteria. Data extraction was performed by four researchers (P.A.-C., A.T.-G., M.C.R.-M., D.R.-A.). Clinical efficacy was defined by whether study results showed that a test or a treatment improved any symptoms [11]. A data-extraction form was developed that included the following data from each study: article title, country, year, author, type of study, sample size, follow-up time, main characteristics of the participants, description of the intervention, main outcomes, and conclusions.