Objective: To develop a label comprehension study (LCS) of package inserts for over-the-counter medications in Japan, we evaluated whether it would be possible to detect differences in the level of understanding due to layout, and font size of different types of package insert using the interview method for LCS we developed previously.
Design: A face-to-face questionnaire investigation.
Methods: Two different types of package insert (including layout, and font size) for H₂-antagonists (package insert groups A and B) were used.  Study participants (≥18 years old) comprised consumers who visited a drugstore with a dispensing service in Saitama Prefecture.  They were randomly assigned to group A or B and divided by age range (young, 18-39 years; middle-aged, 40-59 years; eldely, ≥60 years).  First, the volunteers read the package insert with no time limitation and then answered 14 scenario-type questions during an interview to determine the level of understanding of the insert.  When both the correct answer and correct reason were given, the response was judged as correct.  The level of understanding of the package insert was calculated as the number of persons giving correct responses divided by all respondents.
Results: Questionnaire responses from 86 consumers (43 in each group) were obtained.  The mean age in groups A and B was 46.5 years and 47.0 years, respectively.  The mean level of understanding of the package insert (14 questions) in groups A and B was 50.2 and 38.1%, respectively.  By age range, the mean level of understanding of the package insert in groups A and B in the young group was 60.6 and 56.9%, respectively, and there was no statistically significant difference between the two groups.  However, the mean level of understanding in groups A and B was 56.9 and 35.0% in the middle-aged group and 26.3 and 14.5% in the elderly group, respectively.  The mean understanding in group A was therefore higher than that in group B in both age ranges.  The association between understanding and age within groups indicated that with increasing age, understanding was lower in both groups (group A, p=0.001; group B, p<0.001).  There was no difference in the level of understanding between the young and middle-aged in group A, but the difference in group B was greater than 20%.
Conclusion: By comparing two package inserts of products in a similar pharmacological category using our LCS method, it suggested that font size and layout influenced consumers’ understanding of package inserts.  It might be able to evaluate the difference in the understanding of the package insert by using our LCS method.