Systematic and Other Reviews: Hand Searching

Always Use Hand Searching

Relying on database searching alone introduces two types of bias which can influence your findings at the search stage:

1. Indexing bias – the major databases index a specific range of journals, not everything of value.

2. Publication bias – studies with statistically significant findings have a greater chance of being published which leaves approximately half of all studies left unpublished. Databases only index ‘published’ content.

These two biases can be controlled by incorporating hand searching and grey literature into your search strategy.

How to Hand Search

There are a number of hand searching methods, and not all of them may be suitable for your review. Consider the types of studies and sources you need, and select hand searching strategies accordingly.

After hand searching, add your selected articles to your screening software for inclusion in the review. Download the citation from a database like Google Scholar.

Citation chaining tracks the articles that have referenced a key article. This methods easily identifies papers that have not turned up in database searches, and can even show flaws in the search strategy that need fixing.

Use this method late in the screening stage after you have identified included papers. There are two types of citation chaining:

• Backwards chaining: Looking at reference lists of key articles. Incorporate these into your screening.
• Forwards chaining: Use platforms like Google Scholar or Scopus to look up your included papers. These platforms show future articles that cite your chosen papers. Incorporate these into your screening.

This method identifying key journals and looking through the table of contents pages for relevant articles. The strength of this approach is that you can pick up papers that might not match perfectly to your search results. This method can also identify issues with the search design.

You can use colleague/supervisor recommendations, faculty whitelists, journal rankings/categories, and the results of your database search to identify key journals.

• Lead Authors: Searching all works by prominent authors relevant to your research question.
• Lead Organisations: Searching the websites, libraries or repositories of lead organisations relevant to the research question for additional material.
• Unpublished Material: Contacting authors of key studies for additional unpublished material controls for publication bias.

Chapter Summary