Validation of the PRUCISION Instruments in Pediatric Patients with Progressive Familial Intrahepatic Cholestasis

Plain Language Summary Progressive familial intrahepatic cholestasis (PFIC) is a collection of liver diseases that typically affects very young children. A problematic symptom of PFIC is extremely itchy skin, or pruritus, that can keep patients and their families up at night. The PRUCISION questionnaire was developed to measure the severity of a patient's pruritus and sleep disturbance from the perspective of the patient's caregiver. The current study had two primary goals: (1) to assess whether PRUCISION could reliably measure these symptoms and detect changes over time relative to other established rating scales that assess related concepts, and (2) to identify what score change on PRUCISION could be considered clinically meaningful. To do this, data from a clinical study, called PEDFIC 1, in patients with PFIC were used: patient's scores on PRUCISION from their caregiver's perspective were compared with scores on other established scales, first before any treatment was given in PEDFIC 1, and then again after 24 weeks of treatment with a drug called odevixibat. In general, there was good agreement between PRUCISION scores and scores on other scales. For example, when PRUCISION scores indicated that symptoms improved, this tended to correlate with improvement on other measures. Additionally, these analyses indicated that if the PRUCISION score drops by 1 point or more, that can be considered a clinically important change. Overall, this study found that the caregiver-reported PRUCISION questionnaire is valid for assessing changes in pruritus and sleep symptoms in patients with PFIC, which may benefit patients as new treatments are developed. Introduction Patients with cholestatic liver disease, including progressive familial intrahepatic cholestasis (PFIC) and Alagille syndrome, may have debilitating pruritus, and reducing pruritus is a key therapeutic goal. However, few instruments are available that adequately measure pruritus in pediatric patients with cholestatic liver disease. The objectives of the current study were to establish the measurement properties of the novel PRUCISION patient-reported outcome (PRO) and observer-reported outcome (ObsRO) instruments and to estimate a threshold for clinically meaningful change in pruritus score. Methods The PRO/ObsRO instruments are completed twice daily via electronic diary and include 5-point pictorial responses to assess pruritus. Sleep disturbance and tiredness were quantified using 5-point pictorial responses, yes/no responses, and numerical ratings. Data from PEDFIC 1 (NCT03566238), a phase 3 study evaluating odevixibat efficacy and safety in children with PFIC, were used to assess the psychometric properties of these instruments. Quantitative assessments included evaluation of test-retest reliability, determination of construct validity via convergent and known-group validity analyses, and characterization of sensitivity to change. A threshold for within-patient meaningful change from baseline to week 24 was determined using blinded data from PEDFIC 1 and distribution- and anchor-based analyses. Results Because the majority of patients in PEDFIC 1 were aged < 8 years (n = 52/62) and thus too young to complete the PRO instrument, which was intended for patients aged >= 8 years, the small sample size of patients who completed the PRO precluded a full psychometric analysis of the PRO instrument. The ObsRO was completed by a caregiver of every patient in PEDFIC 1. The ObsRO instrument had acceptable test-retest reliability based on intraclass correlation values (most > 0.75). Convergent validity analyses revealed moderate-to-strong correlations (r >= 0.3) between baseline ObsRO pruritus scores and baseline Global Impression of Symptoms (GIS) items. In known-groups validity analyses, there were significant differences between baseline groups defined by the GIS for ObsRO pruritus scores and for some sleep disturbance scores. Week 24 ObsRO scores were in the expected direction in groups defined by the Global Impression of Change scale (i.e., improved or not improved); many mean differences between these groups were significant. Sensitivity to change for the ObsRO PRUCISION instrument was also demonstrated by moderate-to-strong Pearson correlations between change from baseline to weeks 21-24 in ObsRO scores and GIS items (r >= 0.3). Based on these analyses, a within-patient change of -1.00 from baseline in ObsRO pruritus score was determined to be clinically meaningful. Conclusion The PRUCISION ObsRO instrument is reliable, valid, and sensitive to change, supporting its use as a tool to measure pruritus and sleep disturbance in patients with PFIC and other pediatric cholestatic liver diseases.