Content Validity and Cognitive Debriefing of a Patient-Reported Outcome Instrument Evaluating Symptoms and Disease Impact in Patients with Geographic Atrophy

Abstract

Introduction: Geographic atrophy (GA) occurs in the later stages of dry age-related macular degeneration (AMD) and impairs visual acuity, eventually causing permanent blindness in some patients and impacting patient quality of life. Patient-reported outcome (PRO) measures that assess the experience of patients with visual impairment do not sufficiently capture all concepts salient to patients with GA. In this study the experience of patients with GA secondary to dry AMD was evaluated, and items from the novel 10-item Visual Impairment Symptom Severity Assessment (VISSA-10) PRO instrument were mapped to salient symptoms to assess its content validity, ease of use, and relevance.

Methods: Concept elicitation interviews were conducted with patients with GA to determine salient symptoms and impacts of GA, and a conceptual model was developed to reflect these. The items in the VISSA-10 instrument were then mapped onto the salient symptoms included in this conceptual model. Cognitive debriefing interviews were also conducted with the same cohort to determine the comprehensiveness and comprehensibility of the instrument, and to qualitatively assess levels of change considered meaningful by patients.

Results: In total, 25 symptoms and 36 impacts were reported by 19 patients with GA, with seven symptoms and 11 impacts identified as salient. Of these, 12 symptoms and 15 impacts reported were not included in a previously published conceptual model for patients with dry AMD. Overall, eight of the ten items from the VISSA-10 instrument mapped to salient symptoms reported by patients with GA. All patients reported that the instrument was clear and easy to understand.

Conclusions: The VISSA-10 instrument was shown to be content valid, clear, and comprehensible, with sufficient concept coverage to measure the experience of patients with GA. Although further quantitative validation is required, this instrument has demonstrated potential for implementation in future clinical trials to evaluate the efficacy of new treatments for GA.

Keywords: Clinical outcomes assessment; Cognitive debriefing; Content validity; Geographic atrophy; Patient-reported outcomes; Vision; Visual acuity.

Fig. 1

Frequency map of reported symptoms versus average disturbance rating for patients with geographic atrophy secondary to dry age-related macular degeneration (AMD). Asterisk indicates a symptom not included in the dry AMD population conceptual disease model [17]. Disturbance was assessed on a 0–10 scale where 0 = “not at all disturbing” and 10 = “extremely disturbing”. Symptoms for which a disturbance rating was not supplied are not reflected in this figure. A symptom was deemed “salient” if it was mentioned by ≥ 50% of patients and the average disturbance rating was ≥ 5. Average disturbance ratings are based on the number of patients who provided a rating, which is not always the same as the number of patients who endorsed the impact. Some patients provided qualitative descriptions and even with gentle encouragement by the interviewer would not provide a numeric disturbance rating. “Fatigue” reported by patients as “general fatigue” is not specific to eyesight or eyes. Only one patient provided a disturbance rating for “line distortion”

Fig. 2

Frequency map of reported impact versus average disturbance rating for patients with geographic atrophy secondary to dry age-related macular degeneration (AMD). Asterisk indicates that the impact was not included in the dry AMD population conceptual disease model [17]. Disturbance was assessed on a 0–10 scale where 0 = “not at all disturbing” and 10 = “extremely disturbing”. Impacts for which a disturbance rating was not supplied are not reflected in this figure. An impact was deemed “salient” if it was mentioned by ≥ 50% of patients and the average disturbance rating was ≥ 5. Average disturbance ratings are based on the number of patients who provided a rating, which is not always the same as the number of patients who endorsed the symptom. Some patients provided qualitative descriptions and even with gentle encouragement by the interviewer would not provide a numeric disturbance rating

Fig. 3

Conceptual model reflecting symptoms and impacts relevant to patients with geographic atrophy (GA) secondary to dry AMD. 2D Two dimensions, 3D three dimensions. ^aSchultz et al. [17]. Salient concepts were mentioned by ≥ 50% of patients and had an average disturbance rating ≥ 5

Fig. 4

Absolute change in total 10-item Visual Impairment Symptom Severity Assessment (VISSA-10) score representing meaningful change for patients with geographic atrophy secondary to dry age-related macular degeneration. One patient ended the interview before this question was reached. Absolute changes in total VISSA-10 scores representing meaningful worsening are displayed in orange, and those representing meaningful improvement are displayed in blue. Scores are on a “0”–“100” scale of visual difficulties where “0” = “no visual difficulties” and “100” = “the most extreme of visual difficulties”