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Vol. 42. Num. 7.October 2018
Pages e16-e18Pages 397-460
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Vol. 42. Num. 7.October 2018
Pages e16-e18Pages 397-460
DOI: 10.1016/j.medine.2017.10.012
Systematic review and meta-analysis
Revisión sistemática y metaanálisis
M. Delgado-Rodrígueza,b,
Corresponding author

Corresponding author.
, M. Sillero-Arenasc
a Catedrático de Medicina Preventiva y Salud Pública, Universidad de Jaén, Jaén, Spain
b Director Científico, CIBER de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
c Asesor Técnico, Delegación Provincial de Salud, Jaén, Spain
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Figures (3)
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Tables (6)
Table 1. Notation of a study with binary variables (exposure and outcome).
Table 2. Measures of association for binary variables.
Table 3. Meta-analysis on the comparison between application of non-invasive ventilation (NIV) and standard oxygen therapy (SO) in adults with acute hypoxemic nonhypercapnic respiratory failure; the outcome is intubation rate.24
Table 4. Weights for each study of the example in Table 3 using the inverse of variance method for the fixed effects model (FEM) and the random effects model (REM).
Table 5. Questions to be considered in the election between a fixed effects model (FEM) and a random effects model (REM) (sources: 9,56–59).
Table 6. The AMSTAR scale for evaluating systematic reviews.15
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In this review the usual methods applied in systematic reviews and meta-analyses are outlined. The ideal hypothesis for a systematic review should be generated by information not used later in meta-analyses. The selection of studies involves searching in web repertories, and more than one should be consulted. A manual search in the references of articles, editorials, reviews, etc. is mandatory. The selection of studies should be made by two investigators on an independent basis. Data collection on quality of the selected reports is needed, applying validated scales and including specific questions on the main biases which could have a negative impact upon the research question. Such collection also should be carried out by two researchers on an independent basis. The most common procedures for combining studies with binary outcomes are described (inverse of variance, Mantel-Haenszel, and Peto), illustrating how they can be done using Stata commands. Assessment of heterogeneity and publication bias is also illustrated with the same program.

Systematic reviews
Publication bias

En esta revisión se detallan los métodos habituales que se aplican en una revisión sistemática con metaanálisis. La hipótesis ideal para una revisión sistemática es la generada por el material científico que no formará parte del metaanálisis. La selección de los estudios supone la búsqueda en más de un repertorio en la web. Es obligatoria una búsqueda manual en la bibliografía de artículos, editoriales, revisiones, etc. La selección de los estudios debería hacerse por 2 investigadores independientes. Hay que reunir información sobre la calidad de los estudios, aplicando escalas validadas en las que deben constar preguntas específicas sobre los sesgos que pueden amenazar a la pregunta de investigación, por 2 investigadores independientes. Se describen los métodos más comunes para combinar estudios con efectos binarios (inverso de la varianza, Mantel-Haesnzel y Peto), y se muestra cómo hacerlo con comandos de Stata. La valoración de la heterogeneidad y del sesgo de publicación se ilustran con el mismo programa.

Palabras clave:
Revisión sistemática
Sesgo de publicación


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