Predictors of Flares in Recent-Onset Psoriatic Arthritis. Results of a Multivariable Model Based on Machine Learning

Abstract Background Predicting the occurrence of a flare using tools and information that are readily available in daily clinical practice would provide added value in disease management. Scarcely any studies address this issue. The aim was to identify patient- and disease-related characteristics predicting flares in recent-onset PsA. Methods We performed a multicenter observational prospective study (2-year follow-up, regular annual visits). The study population comprised patients aged ≥ 18 years, fullfilling the CASPAR criteria and less than 2 years since the onset of symptoms. Flares were defined as inflammatory episodes affecting the axial skeleton and/or peripheral joints (joints, digits or entheses), diagnosed by a rheumatologist. The dataset contained data for the independent variables from the baseline visit and from follow-up visit number 1. These were matched with the outcome measures from follow-up visits 1 and 2, respectively. We trained a logistic regression model and random forest–type and XGBoost machine learning algorithms to analyze the association between the outcome measure and the variables selected in the bivariate analysis. A k-fold cross-validation with k = 5 was performed. Results At the first follow-up visit, 37.6% of the patients who attended the clinic had experienced flares since the baseline visit. Of those who attended the second visit, 27.4% had experienced flares since the first visit. The number of observations for the multivariate analysis was 295.The variables predicting flares between visits were PsAID, number of digits with onychopathy, age-adjusted Charlson comorbidity index and level of physical activity. The mean values of the measures of validity of the machine learning algorithms were all high, especially sensitivity (95.71%. 95% CI: 79.84–100.00). Conclusions These findings provide guidance not only on general measures (regular physical activity), but also on therapy (drugs addressing nail disease).