[How can we measure cancer literacy?--A systematic review on the quality of available measurement tools].

Background And Objectives: Health literacy denoted as the ability to search for, understand and use health related information in health care decision-making is becoming increasingly important for complex chronic diseases such as cancer. There is growing evidence that limited health literacy has a negative impact on individual cancer prevention and disease coping behavior suggesting that interventions for quality assurance in cancer care should consider the health literacy of the target population. This poses the question of how cancer literacy should be operationalized and measured.

Methods: We conducted a systematic review on available instruments to measure cancer literacy. The review was performed according to the PRISMA guideline. Relevant instruments were categorized and evaluated in regard to construct definition, operationalization approach and psychometric properties.

Results: Overall, N=12 publications reporting on the development and validation of a cancer literacy instrument could be identified. Cancer literacy is defined as the ability to search for, understand and use health related information in health care decision-making (health literacy) or as the knowledge a layperson needs to understand the information and advice the health system offers with regard to preventing, diagnosing and treating cancerous conditions. In most cases, cancer literacy is operationalized by using cancer knowledge tests across distinct knowledge areas. The analysis of the psychometric properties yields the finding that only every second paper (N=6) is reporting reliability and validity data. Altogether, reliability data is quite satisfactory whereas construct and criterion validity data demonstrates low to moderate correlations between the instruments developed and external criteria as well as comparative instruments.

Conclusion: The aspect of cancer literacy is gaining relevance in terms of its contribution to quality assurance and patient safety. Currently, there are a limited number of cancer literacy instruments available. Definitions of constructs and instrument conceptions mostly rely on the aspect of cancer knowledge making it difficult to differentiate cancer literacy from cancer knowledge. Prospective studies should take greater account of more sophisticated measurement approaches used to assess health literacy.