Abstract 22 — Derivation and Internal Validation of a Multi-Biomarker-Based Disease Activity Prediction Score for Psoriatic Arthritis Patients

Background While C-reactive protein (CRP) is commonly used to monitor disease activity in Psoriatic Arthritis (PsA), over half of the patients with moderate-to-high disease activity had normal CRP level. Our study aims to investigate the correlation of serum protein biomarkers and disease activity in patients with PsA. Methods 176 patients fulfilled the CASPAR (ClASsification criteria for Psoriatic ARthritis) were recruited in this cross-sectional study. Disease activity was measured by the clinical Disease Activity in Psoriatic Arthritis (cDAPSA). 45 protein biomarkers, cartilage and bone turn-over markers level were assessed (Table 1). The patients were randomly divided into a derivation-cohort and a validation-cohort at a ratio of 7:3. Least absolute shrinkage and selection operator (LASSO) was used to select biomarkers which were associated with moderate/high disease activity in the derivation cohort. Receiver operating characteristic (ROC) curve, GiViTI calibration belt were used to assess the performance of the model in both cohorts. Results The cohort [age: 55.5 (44.0-62.75) years, male: 80 (45.5%)] had moderate disease activity [DAPSA: 15.9 (8.3-26.9); PASI: 3.2 (0.5-6.8)]. 101 PsA patients (57.4%) had moderate/high disease activity. Biomarker levels associated with moderate/high disease activity included SAA (Serum amyloid A), IL8 (Interleukin 8), IP10 (Interferon gamma-induced protein 10), M-CSF (Macrophage colony-stimulating factor), SCGF- β (Stem cell growth factor), SDF-1 α (Stromal cell-derived factor 1 α ) (Figure 1A, B). The model’s equation including the 6 biomarker levels was applied to the validation-cohort. The area under the ROC curve (AUC) for discriminating moderate/high disease activity was 0.802 and 0.835 for the derivation-and-validation-cohorts, respectively (Figure 1C, D). The multi-biomarkers panel model had higher-AUC when compared with that of CRP (AUC=0.727, p=0.022). The P-values of calibration charts in the two sets were 0.902 and 0.123 (Figure 1E, F). Conclusions The multi-biomarkers panel had excellent performance in discriminating patients with moderate/high disease activity from those with low disease activity/remission.