Differentiating Psoriatic Arthritis From Psoriasis Without Psoriatic Arthritis Using Novel Serum Biomarkers

Objective

There is a high prevalence of undiagnosed psoriatic arthritis (PsA) in patients with psoriasis. Identifying soluble biomarkers for PsA will help in screening psoriasis patients for appropriate rheumatology referral. We therefore aimed to investigate whether serum levels of novel markers previously discovered by quantitative mass spectrometric analysis of synovial fluid and skin biopsies performs better than the C‐reactive protein (CRP) level in differentiating PsA patients from those with psoriasis without PsA (PsC).

Methods

In this case–control study, serum samples were obtained from 100 subjects with PsA, 100 with PsC, and 100 healthy controls. Patients with PsA and PsC were group matched for age, sex, psoriasis duration, and Psoriasis Area and Severity Index and were not currently receiving biologic treatment. Using enzyme‐linked immunosorbent assay, 4 high‐priority markers (Mac‐2‐binding protein [M2BP], CD5‐like protein [CD5L], myeloperoxidase [MPO], and integrin β5 [ITGβ5]), as well as previously established markers (matrix metalloproteinase 3 [MMP‐3] and CRP level) were assayed. Data were analyzed using logistic regression. Receiver operating characteristic (ROC) curves were plotted.

Results

In comparisons to controls, CD5L, ITGβ5, M2BP, MPO, MMP‐3, and CRP level were independently associated with PsA, while only CD5L, M2BP, and MPO were independently associated with PsC alone. In comparisons to PsC, ITGβ5, M2BP, and CRP level were independently associated with PsA. ROC analysis of this model shows an area under the curve (AUC) of 0.85 (95% confidence interval [95% CI] 0.80–0.90). The model that included CRP level alone had an AUC of 0.71 (95% CI 0.64–0.78).

Conclusion

CD5L, ITGβ5, M2BP, MPO, MMP‐3, and CRP level are markers for PsA. The combination of ITGβ5, M2BP, and CRP level differentiates PsA from PsC, and performs better than CRP level alone.

     

Update on Biomarkers in Psoriatic Arthritis

Biomarkers in psoriatic arthritis (PsA) may serve as surrogate end points for disease outcome and can provide insights into disease susceptibility and natural history. Biomarkers could relate to diagnosis, pathogenesis, prognosis, therapeutic response, and comorbidities. The “felt need” is, however, in the development of biomarkers for the presence of PsA in patients with psoriasis, as well as that for joint damage. During the past few years, many studies related to PsA biomarkers have been conducted. These studies are reviewed here. C-reactive protein, matrix metalloproteinase-3, and circulating osteoclast precursors show promise. An international goal-directed study to determine biomarkers for joint damage in PsA is now under way through a collaborative effort of GRAPPA (the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis) and OMERACT (Outcome Measures for Rheumatology Clinical Trials).     

Altered Bone Biology in Psoriatic Arthritis

Psoriatic arthritis (PsA) is characterized by focal bone erosions mediated by osteoclasts at the bone-pannus junction. The bulk of research over the past decade has centered on mechanisms that underlie osteoclastogenesis along with new insights into osteoimmunology; however, recent advances that focus on steps that lead to new bone formation are beginning to emerge. New revelations about bone formation may have direct relevance to PsA given the presence of enthesophytes, syndesmophytes, and bony ankylosis frequently observed in patients with this disorder. In this review, we discuss current developments in the pathogenesis of new bone formation, novel imaging approaches to study bone remodeling and highlight innovative approaches to study the effect of inflammation on bone. Lastly, we discuss promising therapies that target joint inflammation and osteitis with the potential to mediate pathologic bone formation.     

Psoriatic Arthritis: Pharmacotherapy Update

Psoriatic arthritis is a systemic disorder that causes chronic pain, altered physical appearance, and loss of function. The clinical features are diverse, but the core manifestations are psoriasis, peripheral arthritis, axial disease, enthesitis, and dactylitis. Our understanding about the psoriatic arthritis disease state, assessment, and treatment has advanced thanks to significant collaborative efforts by rheumatologists and dermatologists in the development of classification criteria, outcome measures to assess the various clinical domains, and treatment trials with agents also used for diseases such as rheumatoid arthritis and psoriasis. In particular, biologic agents, especially anti-tumor necrosis factor agents, have demonstrated significant efficacy and reasonable safety in all clinical domains of the disease, resulting in amelioration of clinical symptoms, inhibition of structural damage, and improvement in function and quality of life.