Readability of informed consent documents (1987-2007) for clinical trials: a linguistic analysis

We investigated the readability of informed consent documents linguistically and compared old and new ICDs. Twenty ICDs (ten from 1987-1992 and ten from 2006-2007) were included. The Evaluative Linguistic Framework (ELF) was used to analyze the texts. The ELF evaluates the following items: main themes, order of themes, rhetorical functions, the relationship between reader and writer, metadiscourse, headings, expert terminology, and visual aspects. An ICD is considered readable if it achieves the goal of inviting the reader to participate and explaining the implication of participation. The new ICDs were more readable than the old ones, as they were more oriented towards research, contained instructions about how to consent, and provided clear contact information. Aspects that reduced the readability of the new ICDs were the large number of topics, details, and actors presented. The readability of the old ICDs was enhanced by fewer topics, a clear presentation of the involved actors, and brevity. However, their readability was reduced by the inclusion of a vast amount of information about the reader's diagnosis and treatment.