Psychometric Validation of the Sunlight Exposure Diary and Erythropoietic Protoporphyria Impact Questionnaire (EPIQ) Using Data from the AURORA Clinical Study in Erythropoietic Protoporphyria (EPP)
Author(s)
Susan D. Mathias, MPH1, Michelle P. Turner, MS1, Megan O'Grady, PhD2, Chelsea Norregaard, PhD, MPH2, Hilary H. Colwell, MPH1, William Savage, MD, PhD2, Hetanshi Naik, PhD3, Melanie Chin, PhD2.
1Health Outcomes Solutions, Palm Beach Gardens, FL, USA, 2Disc Medicine, Watertown, MA, USA, 3Stanford University, Palo Alto, CA, USA.
1Health Outcomes Solutions, Palm Beach Gardens, FL, USA, 2Disc Medicine, Watertown, MA, USA, 3Stanford University, Palo Alto, CA, USA.
Presentation Documents
OBJECTIVES: To evaluate the psychometric properties of two patient-reported outcome (PRO) measures in individuals with erythropoietic protoporphyria (EPP), a rare genetic disorder leading to phototoxicity, the Sunlight Exposure Diary and EPP Impact Questionnaire (EPIQ).
METHODS: Data were analyzed from AURORA, a randomized, double-blind, placebo-controlled study of bitopertin in EPP. Exploratory factor analysis (EFA) was conducted to evaluate the scale structure of the measures. Reliability (internal consistency, test-retest), validity (construct via correlations with PROMIS measures, known groups based on categorized symptom severity and time to prodrome), responsiveness (effect sizes), and meaningful change (distribution- and anchor-based) were evaluated. Scale scores ranged from 0 to 100, where higher scores indicate better outcomes.
RESULTS: Data were available from 65 adults with EPP (mean age 45, 51% male). EFA supported domains for Duration of Full Phototoxic Reaction (DFR), Overall Change (OC), and Overall Severity and Impact (OSI). A single item, Daily Daylight Tolerance (DDT), was evaluated over two-week (TWI) and one-month (MON) intervals. Reliability was acceptable for DFR, OC, and OSI (Cronbach’s alpha ≥0.70). The DDT-TWI and OC had acceptable test-retest reliability (ICC >0.75), but OSI was weaker (0.62). Mean OSI scores differed between symptom severity and time to prodrome groups, while DDT-TWI only differentiated by time to prodrome. DFR and OC did not significantly differ by known groups. Construct validity was generally as expected. OSI was most responsive, while DDT-TWI was least responsive to change. Small sample sizes and missing baseline data limited meaningful change calculations, prompting the assessment of DDT-MON, which performed more robustly and identified a 13-point change as meaningful improvement. High ceiling effects were noted, indicating that a substantial portion of respondents scored at the upper limit of these measures.
CONCLUSIONS: Overall, the Sunlight Exposure Diary and EPIQ are reliable and valid, supporting their use in future EPP clinical research.
METHODS: Data were analyzed from AURORA, a randomized, double-blind, placebo-controlled study of bitopertin in EPP. Exploratory factor analysis (EFA) was conducted to evaluate the scale structure of the measures. Reliability (internal consistency, test-retest), validity (construct via correlations with PROMIS measures, known groups based on categorized symptom severity and time to prodrome), responsiveness (effect sizes), and meaningful change (distribution- and anchor-based) were evaluated. Scale scores ranged from 0 to 100, where higher scores indicate better outcomes.
RESULTS: Data were available from 65 adults with EPP (mean age 45, 51% male). EFA supported domains for Duration of Full Phototoxic Reaction (DFR), Overall Change (OC), and Overall Severity and Impact (OSI). A single item, Daily Daylight Tolerance (DDT), was evaluated over two-week (TWI) and one-month (MON) intervals. Reliability was acceptable for DFR, OC, and OSI (Cronbach’s alpha ≥0.70). The DDT-TWI and OC had acceptable test-retest reliability (ICC >0.75), but OSI was weaker (0.62). Mean OSI scores differed between symptom severity and time to prodrome groups, while DDT-TWI only differentiated by time to prodrome. DFR and OC did not significantly differ by known groups. Construct validity was generally as expected. OSI was most responsive, while DDT-TWI was least responsive to change. Small sample sizes and missing baseline data limited meaningful change calculations, prompting the assessment of DDT-MON, which performed more robustly and identified a 13-point change as meaningful improvement. High ceiling effects were noted, indicating that a substantial portion of respondents scored at the upper limit of these measures.
CONCLUSIONS: Overall, the Sunlight Exposure Diary and EPIQ are reliable and valid, supporting their use in future EPP clinical research.
Conference/Value in Health Info
2025-05, ISPOR 2025, Montréal, Quebec, CA
Value in Health, Volume 28, Issue S1
Code
MSR61
Topic
Methodological & Statistical Research
Disease
No Additional Disease & Conditions/Specialized Treatment Areas, SDC: Rare & Orphan Diseases