Biomarkers in Relation to Disease Manifestations in Psoriatic Arthritis

Background: In psoriatic arthritis (PsA), a complex disease with a lack of measurable laboratory parameters, there is a need for diagnostic and prognostic tools to meet the challenge of early diagnosis and assessment of disease severity. Objective: To analyze whether soluble biomarkers could discriminate between disease phenotypes in PsA. Methods: Two-hundred and seventy-four patients with established disease and 30 healthy controls were included in this cross-sectional study. Thirty-nine different serological biomarkers were investigated in relation to disease activity, disease manifestations and in comparison with controls. In addition to standard statistical methods, orthogonal partial least squares discriminant analysis (OPLS-DA) was used to investigate different phenotypes of PsA. Results: Psoriatic arthritis activity was significantly associated with CRP (pc = 0.0008), IL-6 (pc = 0.001), IL-16 (pc = 0.007), calprotectin (pc = 0.014), IL-12/IL-23p40 (pc = 0.02), and ICAM-1 (pc = 0.045). Different PsA disease phenotypes were associated with different biomarkers, e.g., axial disease (with or without peripheral disease) was associated with IL-6 (pc = 0.044), IL-16 (pc = 0.044), MIP-1β (pc = 0.039) and polyarthritis was associated with IL-6 (pc = 0.0006), SAA (pc = 0.009), CRP (pc = 0.012) and IL-8 (pc = 0.04), although it was not possible to statistically separate the different phenotypes with OPLSDA. An association was also seen in patients with PsA who, at any time had been prescribed bDMARD, (TNFβ (pc = 0.0001), TNFα (pc = 0.0003), calprotectin (pc = 0.0009), CRP (pc = 0.016) and lower levels of Tie-2 (pc = 0.027)). No significant differences were detected when PsA patients were compared with healthy controls. Conclusions: In this study, inflammatory/pro-inflammatory biomarkers were associated with different disease phenotypes in PsA, however the impact of the various biomarkers is not evident as OPLS-DA analyses could not separate between groups.