title: [Clinical research XXIII. From clinical judgment to meta-analyses].
abstract: Systematic reviews (SR) are studies made in order to ask clinical questions based on original articles. Meta-analysis (MTA) is the mathematical analysis of SR. These analyses are divided in two groups, those which evaluate the measured results of quantitative variables (for example, the body mass index -BMI-) and those which evaluate qualitative variables (for example, if a patient is alive or dead, or if he is healing or not). Quantitative variables generally use the mean difference analysis and qualitative variables can be performed using several calculations: odds ratio (OR), relative risk (RR), absolute risk reduction (ARR) and hazard ratio (HR). These analyses are represented through forest plots which allow the evaluation of each individual study, as well as the heterogeneity between studies and the overall effect of the intervention. These analyses are mainly based on Student's t test and chi-squared. To take appropriate decisions based on the MTA, it is important to understand the characteristics of statistical methods in order to avoid misinterpretations.
authors.affiliation: Centro de Adiestramiento en Investigación Clínica (CAIC), Coordinación de Investigación en Salud, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Distrito Federal, México. rivasrodolfo@gmail.com.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Rivas-Ruiz
authors.forename: Osvaldo D
authors.initials: OD
authors.lastname: Castelán-Martínez
authors.forename: Marcela
authors.initials: M
authors.lastname: Pérez-Rodríguez
authors.forename: Lino
authors.initials: L
authors.lastname: Palacios-Cruz
authors.forename: Maura E
authors.initials: ME
authors.lastname: Noyola-Castillo
authors.forename: Juan O
authors.initials: JO
authors.lastname: Talavera
mesh_terms: D035843:Biomedical Research; D006801:Humans; D015201:Meta-Analysis as Topic; D012196:Review Literature as Topic
keywords: Forest plots; Meta-Analysis; Review, Systematic