Which of the following is NOT a type of evidence indicated in the hierarchy of evidence?

The concept of a hierarchy of evidence is fundamental in nursing research and evidence-based practice, as it ranks different types of research studies based on the strength and reliability of their evidence. Typically, at the top of this hierarchy are systematic reviews and meta-analyses of randomized controlled trials, followed by randomized controlled trials themselves, cohort studies, case-control studies, and finally single descriptive studies.

Literature synthesis refers to a comprehensive overview or a summary of existing literature on a particular topic, bringing together findings from various studies. While it provides valuable insights and contextual understanding, it does not constitute original research nor does it fit into the ranks of primary research evidence. Instead, it acts as an aggregate of previously published works.

In contrast, randomized controlled trials, case-control studies, and single descriptive studies are accepted types of research that contribute directly to the hierarchy of evidence. Each of these, while varying in rigor and methodology, provides data that can influence clinical practice based on empirical findings. As a result, literature synthesis does not fit into the established categories of primary research evidence and is therefore regarded as not a type of evidence within the hierarchy.