Objectives
There are multiple instruments that have been developed to direct the formatting and design of patient education materials to enhance readability. The aim of this study was to compare and contrast validated tools available to guide the formatting and readability of patient information materials.

Methods
The primary objective of this narrative review was to identify tools to assess readability and legibility of health information. Online databases, including MEDLINE, Pubmed, ERIC, HAPI, EMBASE, and Web of Science, were searched for relevant publications. These sources were searched for papers containing the terms readability, legibility, font, typography, health education, patient education, health material, consumer health information, tool, instrument, test, scale, assess, measure, and valid. The publications relating to these tools were reviewed and data abstracted about the tool characteristics (including content and format of assessment, administration time, advantages, disadvantages).

Results
Twenty readability formulas and seven legibility tools met the inclusion criteria. These instruments differ slightly in the variables assessed and formulas utilized. Most tools use a calculation of sentence length or syllables per word. All tools provide some sort of scoring or classification system for level of reading, often relating the level to a grade-school level based on North American education. Only three tools were validated for health information. A common disadvantage is the requirement to buy particular software, and the time consuming nature of reviewing a particular passage or document, and the focus on English language materials.

Conclusion
There is a diversity of tools available that can assist health professionals in designing readable health information for patients. There is not one tool that fully addresses legibility and readability, although the Simple Measure of Gobbledygook Grading (SMOG) may be most useful for patient brochures or leaflets, due to scoring, ease of administration, and high correlation with other readability tools.