Psychometric Validation of the Psoriasis Symptoms and Impacts Measure (P-SIM): A Novel Patient-Reported Outcome Instrument for Patients with Plaque Psoriasis, Using Reported Data from the BE RADIANT Phase 3b Trial

Abstract

Introduction: This analysis assessed the psychometric properties of the Psoriasis Symptoms and Impacts Measure (P-SIM), a novel patient-reported outcome (PRO) tool designed to capture patient experiences of the signs, symptoms and impacts of psoriasis.

Methods: Blinded data from the BE RADIANT phase 3b trial of bimekizumab were analysed. In BE RADIANT, patients were randomised 1:1 to bimekizumab 320 mg every 4 weeks (Q4W) or secukinumab 300 mg (weekly until Week 4, then Q4W). Three items (itching, skin pain and scaling) of the P-SIM were electronically assessed throughout the trial and were scored from 0 to 10 (none to very severe signs/symptoms/impacts). Test-retest reliability was determined using intraclass correlations. Convergent validity was assessed between P-SIM and other relevant PRO and clinician-reported outcome (ClinRO) scores. Known-groups validity was assessed by comparing mean P-SIM item scores between patient subgroups based on the Psoriasis Area and Severity Index (PASI)/Investigator's Global Assessment (IGA) scores. Responsiveness was assessed via correlations between changes from baseline in P-SIM item scores and other relevant PRO and ClinRO scores. Anchor-based responder analyses and empirical cumulative distribution function (eCDF) curves determined responder thresholds.

Results: The three P-SIM items yielded high intraclass coefficients (> 0.70). By Week 48, the three P-SIM items had moderate (> 0.30 and ≤ 0.50) to strong (> 0.50) correlations with other PROs and weaker correlations with ClinROs, demonstrating good convergent validity. For almost all known-group comparisons, statistically significant between-subgroup score differences were seen across all three P-SIM items. Changes from baseline in the P-SIM and other relevant outcomes were above the acceptable threshold of ≤ 0.30, demonstrating sensitivity to change. Anchor-based analyses determined a ≥ four-point reduction from baseline to indicate marked clinically meaningful improvement for the P-SIM.

Conclusion: These results support the validity, reliability and sensitivity to change of the P-SIM in assessing key symptoms (itching, skin pain and scaling) in patients with moderate to severe plaque psoriasis.

Trial registration: NCT03536884.

Keywords: Bimekizumab; Patient-reported outcome; Psoriasis; Psychometric validation.

© 2021. The Author(s).

Figures

Fig. 1

In BE RADIANT, patients were randomised 1:1 to bimekizumab 320 mg Q4W or secukinumab 300 mg weekly to Week 4 then Q4W. Patients randomised to bimekizumab 320 mg Q4W either continued to receive Q4W dosing at Week 16 or switched to Q8W maintenance dosing. Secukinumab dosing was 300 mg at Weeks 0, 1, 2, 3 and 4, and Q4W thereafter. After completing the 48-week double-blinded period, patients could enrol in a 96-week open-label extension period to assess the long-term safety, tolerability and efficacy of bimekizumab. Patients who did not enrol in the open-label extension underwent a safety follow-up visit 20 weeks after their last dose of study treatment. PASI 100 100% improvement from baseline Psoriasis Area and Severity Index, Q4W every 4 weeks, Q8W every 8 weeks

Fig. 2

P-SIM item scores at Week 16, 32 and 48 by PASI total score. a P-SIM Item 1—itching. b P-SIM Item 3—skin pain. c P-SIM Item 5—scaling. Black circular markers indicate mean scores and blue circular markers indicate outliers. PASI Psoriasis Area and Severity Index, P-SIM Psoriasis Symptoms and Impacts Measure

Fig. 3

P-SIM item scores at Week 16, 32 and 48 by IGA score subgroup. a P-SIM Item 1—itching. b P-SIM Item 3—skin pain. c P-SIM Item 5—scaling. Black circular markers indicate mean scores and blue circular markers indicate outliers. IGA Investigator’s Global Assessment, P-SIM Psoriasis Symptoms and Impacts Measure