Mepolizumab improvements in health-related quality of life and disease symptoms in a patient population with very severe chronic rhinosinusitis with nasal polyps: psychometric and efficacy analyses from the SYNAPSE study

BackgroundAlthough the psychometric properties of patient-reported outcome measures (e.g. the 22-item Sino-nasal Outcomes Test [SNOT-22]) in chronic rhinosinusitis with nasal polyps (CRSwNP) have been defined, these definitions have not been extensively studied in patients with very severe CRSwNP, as defined by recurrent disease despite >= 1 previous surgery and a current need for further surgery. Therefore, the psychometric properties of the symptoms visual analogue scales (VAS) were evaluated, and meaningful within-patient change thresholds were calculated for VAS and SNOT-22.MethodsSYNAPSE (NCT03085797), a randomized, double-blind, placebo-controlled, 52-week trial, assessed the efficacy and safety of 4-weekly mepolizumab 100 mg subcutaneously added to standard of care in very severe CRSwNP. Enrolled patients (n = 407) completed symptom VAS (six items) daily and SNOT-22 every 4 weeks from baseline until Week 52. Blinded psychometric assessment of individual and composite VAS was performed post hoc, including anchor-based thresholds for meaningful within-patient changes for VAS and SNOT-22, supported by cumulative distribution function and probability density function plots. The effect of mepolizumab versus placebo for 52 weeks on VAS and SNOT-22 scores was then determined using these thresholds using unblinded data.ResultsInternal consistency was acceptable for VAS and SNOT-22 scores (Cronbach's alpha-coefficients >= 0.70). Test-retest reliability was demonstrated for all symptom VAS (Intra-Class Correlation coefficients > 0.75). Construct validity was acceptable between individual and composite VAS and SNOT-22 total score (r = 0.461-0.598) and between individual symptom VAS and corresponding SNOT-22 items (r = 0.560-0.780), based upon pre-specified ranges. Known-groups validity assessment demonstrated generally acceptable validity based on factors associated with respiratory health, with all VAS responsive to change. Mepolizumab treatment was associated with significantly increased odds of meeting or exceeding meaningful within-patient change thresholds, derived for this very severe cohort using six anchor groups for individual VAS (odds ratio [OR] 2.19-2.68) at Weeks 49-52, and SNOT-22 (OR 1.61-2.96) throughout the study.ConclusionsSymptoms VAS and SNOT-22 had acceptable psychometric properties for use in very severe CRSwNP. Mepolizumab provided meaningful within-patient improvements in symptom severity and health-related quality of life versus placebo, indicating mepolizumab provides substantial clinical benefits in very severe CRSwNP. Plain English summaryPatients with chronic rhinosinusitis (CRS) often have blocked or runny noses, and loss of sense of smell. They can also have sac-like growths in their nose called nasal polyps, which often require surgical removement. The symptoms of CRS with nasal polyps can affect quality of life. In a clinical study named SYNAPSE, a new treatment option called mepolizumab reduced the size and severity of nasal polyps in patients suffering from very severe CRS with nasal polyps, compared with placebo. Mepolizumab also reduced the need for nasal polyp surgery. The SYNAPSE study also measured if 1 year of mepolizumab treatment improved patients' symptoms and quality of life. This was evaluated by asking patients to complete two separate tasks. These tasks were rating symptoms on a visual analogue scale (VAS) and completing a quality of life questionnaire called SNOT-22. The objective of this analysis was to see if these questionnaires accurately assessed a patient's quality of life. The analysis also assessed how many patients had major improvements in their symptoms with mepolizumab. Overall, data from 407 patients in the SYNAPSE study was analyzed. Results showed that both the VAS and SNOT-22 questionnaires accurately captured CRS symptoms and quality of life. In addition, patients treated with mepolizumab for 1 year had improvements in quality of life compared with placebo. In conclusion, these findings suggest that the VAS and SNOT-22 questionnaires are appropriate evaluation tools for patients with very severe CRS with nasal polyps. The findings also show that mepolizumab treatment is beneficial for these patients.