The expanded prostate cancer index composite short form (EPIC-26) for measuring health-related quality of life: content analysis of patients’ spontaneous comments written in survey margins

INTRODUCTION: This study investigates comments that prostate cancer patients spontaneously write in the margins of the Expanded Prostate Cancer Index Short Form (EPIC-26) questionnaire. We aim to show the possible barriers that patients face while answering the survey, and to consider how these barriers may affect the response data generated. We investigate the kind of information patients’ comments on EPIC-26 contain, and patients’ motivations to provide this information. We also study why some EPIC domains spark more comments than others. METHOD: We analyzed 28 pages of transcribed comments and four pages of supplementary letters from our survey participants (n = 496). Using inductive content analysis, we generated 10 categories describing the content of participants’ comments, and four themes demonstrating their motives for commenting. The comments regarding each EPIC domain were quantified to discover any differences between domains. RESULTS: The sexual domain of EPIC-26 provoked over half of all comments. Patients without recent sexual activity or desire had difficulties answering sexual function questions 8–10. The lack of instructions on whether to take erectile aid use into account when answering erectile function questions led to a diversity of answering strategies. Patients with urinary catheters could not find suitable answer options for questions 1–4. All domains sparked comments containing additional information about experienced symptoms. CONCLUSION: Patients are mainly willing to report their symptoms, but a lack of suitable answer options causes missing data and differing answering strategies in the sexual and urinary domains of EPIC-26, weakening the quality of the response data received. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11136-021-02940-z.