Quantitative alternatives to narrative reviews for understanding existing research literature.

This article is the second in a series that examine the role of literature reviews in rehabilitation research. Methods of generating new knowledge from existing literature are categorized into three approaches: synthetic literature reviews which interpret previous findings in narrative fashion, quantitative literature reviews which summarize findings from primary research studies using a variety "counting" approaches, and meta-analyses which aggregate effect sizes from primary research studies and allow for a more complex analysis of trends in the empirical research literature. This articles examines the role that quantitative literature reviews can play in better understanding the status of knowledge in rehabilitation research, thereby shaping field practices as well as future scientific investigations. Examples of quantitative reviews from contemporary rehabilitation and related health sciences literature are provided throughout the article.