Psychometric Validation of the Modified Low Luminance Questionnaire in Patients With X-Linked Retinitis Pigmentosa
Author(s)
Rebecca Cheng, PharmD, MS1, Hoan Do, PhD1, Leslie Patch, MD, MBA2, Cagri Besirli, MD, PhD2, Michael Clark, MD, MBA2, Katalin Pungor, MD, PhD3, Alexis Oldfield, PhD2, Pamela Berry, MSc4.
1Clinical Outcomes Solutions, Tucson, AZ, USA, 2Johnson & Johnson, Raritan, NJ, USA, 3Janssen-Cilag GmBH, North Rhine-Westphalia, Germany, 4Johnson & Johnson, Horsham, PA, USA.
1Clinical Outcomes Solutions, Tucson, AZ, USA, 2Johnson & Johnson, Raritan, NJ, USA, 3Janssen-Cilag GmBH, North Rhine-Westphalia, Germany, 4Johnson & Johnson, Horsham, PA, USA.
OBJECTIVES: Modifications were made to the Low Luminance Questionnaire to enhance the clarity and relevance of response choices for use in patients with X-Linked Retinitis Pigmentosa (XLRP). This study aimed to evaluate the psychometric properties of the adult version of the modified Low Luminance Questionnaire (mLLQ; 30 items) in the XLRP population.
METHODS: mLLQ data were subject to item-level analyses (including confirmatory factor analysis [CFA] and Rasch), internal consistency reliability, convergent/divergent validity, and known-groups validity using data from a non-interventional study in patients (n=141) with a clinical diagnosis of XLRP from 23 centers across Europe.
RESULTS: Floor effects were identified for 23/30 items (73.7%). Items within the same domain correlated well with one another and with their respective domain. Sixty-three percent (19/30) of the items had a discrimination index that exceeded the threshold of 0.40. The hypothesized 6-factor CFA model provided relatively good fit to the data. Assigning 2 Extreme Lighting items to the Driving domain also demonstrated an improved model-data agreement. Rasch analysis suggested a lack of items to assess patients toward the upper end of the severity spectrum, consistent with the observed floor effects for most items. Every domain of the mLLQ demonstrated excellent internal reliability (Cronbach’s alpha: 0.843 to 0.957). Evidence also indicated excellent convergent and known-groups validity of the mLLQ domains.
CONCLUSIONS: The mLLQ had good measurement properties to assess difficulty experienced by XLRP patients in low luminance and at night and would be a reasonable and fit-for-purpose measure to use in the XLRP population. Future research may include investigating the re-specification of the 2 Extreme Lighting items to the Driving domain.
METHODS: mLLQ data were subject to item-level analyses (including confirmatory factor analysis [CFA] and Rasch), internal consistency reliability, convergent/divergent validity, and known-groups validity using data from a non-interventional study in patients (n=141) with a clinical diagnosis of XLRP from 23 centers across Europe.
RESULTS: Floor effects were identified for 23/30 items (73.7%). Items within the same domain correlated well with one another and with their respective domain. Sixty-three percent (19/30) of the items had a discrimination index that exceeded the threshold of 0.40. The hypothesized 6-factor CFA model provided relatively good fit to the data. Assigning 2 Extreme Lighting items to the Driving domain also demonstrated an improved model-data agreement. Rasch analysis suggested a lack of items to assess patients toward the upper end of the severity spectrum, consistent with the observed floor effects for most items. Every domain of the mLLQ demonstrated excellent internal reliability (Cronbach’s alpha: 0.843 to 0.957). Evidence also indicated excellent convergent and known-groups validity of the mLLQ domains.
CONCLUSIONS: The mLLQ had good measurement properties to assess difficulty experienced by XLRP patients in low luminance and at night and would be a reasonable and fit-for-purpose measure to use in the XLRP population. Future research may include investigating the re-specification of the 2 Extreme Lighting items to the Driving domain.
Conference/Value in Health Info
2025-05, ISPOR 2025, Montréal, Quebec, CA
Value in Health, Volume 28, Issue S1
Code
PCR143
Topic
Patient-Centered Research
Disease
No Additional Disease & Conditions/Specialized Treatment Areas, SDC: Sensory System Disorders (Ear, Eye, Dental, Skin)