Total burden of psoriasis

Physical function, measured by the Health Assessment Questionnaire and Disability Index (HAQ-DI) score at 24 months.

The primary outcome will be analysed using a fixed effects zero-inflated beta regression model adjusting for the stratification factors, HAQ-DI measured at baseline, other relevant baseline covariates, and treatment arm.

1. Disease activity for people diagnosed with psoriatic complications at 24 months post registration. Disease specific questionnaires will be analysed using multivariable fixed effects models, adjusting for the stratification factors and relevant baseline covariates. This will be based on data collected at 24 months post registration.
2. The diagnostic accuracy of an updated symptom questionnaire for identification of psoriatic disease. The diagnostic accuracy of the questionnaire will be assessed by estimating of the sensitivity and specificity, positive and negative predictive values, and AUCs of the questionnaires, against the gold standard for diagnosing psoriatic disease. Regression-based sensitivity analysis, incorporating the possibility of dependence in the outcomes will be utilised to explore the additional explanatory power of the updated questionnaire. This will be measured either at baseline or 24 months depending upon the arm of the study.
3. To compare the sensitivity and specificity of the updated symptom screening tool with the symptom questionnaire currently approved for use in standard care. The differences between the updated and the currently approved questionnaires in terms of their sensitivity and specificity, positive and negative predictive values, and AUCs will be assessed. Where participants have completed both questionnaires, adjusted McNemar's tests, which account for clustered data, will be used to compare sensitivity and specificity. To examine the optimal method for screening for psoriatic disease, diagnostic questionnaires and their different cut points will be compared using receiver operator characteristic (ROC) curve analysis. This will be measured either at baseline or 24 months depending upon the arm of the study.
4. The impact of psoriatic complications on health-related quality of life and work productivity.
Quality of Life and Work Productivity questionnaires will be analysed using a mixed effects model, adjusting
for the stratification factors, other relevant baseline covariates and treatment arm. The model will also adjust for fixed effects as well as random effects where relevant.
5. To identify risk factors associated with a longer duration to diagnosis of psoriasis related health complications. Mixed effects generalised additive models will be used to assess the association between age, sex and psoriasis severity on time to diagnosis in patients diagnosed with psoriasis related health complications, allowing for the possibility of non-linear effects between explanatory variables and response.
6. The association between severity of psoriasis and the development of psoriasis related health complications. The development of psoriasis related health complications will be analysed using a fixed effects zero-inflated beta regression model adjusting for the stratification factors, SAPASI (psoriasis severity measure), HAQ-DI measured at baseline, other relevant baseline covariates and treatment arm, at 24 months post registration.
7. To explore the extent to which certain candidate risk factors are associated with the development of psoriatic disease in people with psoriasis. Mixed effects generalised (logistic) effects models will be used to assess the extent to which age, sex, psoriasis severity, psoriatic disease duration and other risk factors are associated with the development of psoriatic complications in people with psoriasis.
8. The prevalence of inflammatory back pain in people with psoriasis. The prevalence of inflammatory back pain in the trial population will be calculated, together with 95% confidence intervals at baseline and at 12 and 24 months, depending on the arm of the study. The incidence of inflammatory back pain in the ES arms will be calculated, together with 95% confidence intervals at the 12 and 24 month assessments.