The greatest level of evidence-based efficacy of a medical therapy or intervention is provided through meta-analysis. Meta-analyses have shown that allergen immunotherapy, in its two forms of subcutaneous immunotherapy and sublingual immunotherapy (SLIT), is an effective treatment for respiratory allergy. However, there has been an overflow of meta-analyses on SLIT in recent years, with contrasting results that may cause confusion among physicians. It is common to find errors in meta-analyses, such as improper trial selection, wrong use of assessment criteria for the study, and inappropriate analyses. A meta-analysis of numerous small trials, for example, clearly does not anticipate the outcomes of a single big research, which remains the gold standard for determining a treatment’s efficacy and safety. To gauge public interest in the topic, researchers counted the number of citations of meta-analyses on SLIT effectiveness in the ten years after the initial publication in 2005 and found a steady decline in citations.

Today, the appropriateness of a meta-analysis should be carefully considered, because a meta-analysis utilizes a statistical method to integrate the findings of several small studies to enhance power, improve estimates of the size of the impact, and/or clarify doubt when reports differ. Editors and reviewers of medical publications should keep in mind that judging a meta-analysis needs a high degree of competence, which is evident in Cochrane reviewers.

Reference: https://journals.lww.com/co-allergy/Abstract/2017/02000/The_current_overuse_and_misuse_of_meta_analyses_on.4.aspx