Identification and evaluation of serum protein biomarkers which differentiate psoriatic from rheumatoid arthritis

Objectives

To identify serum protein biomarkers which might separate early inflammatory arthritis (EIA) patients with psoriatic arthritis (PsA) from those with rheumatoid arthritis (RA) and may be used to support appropriate early intervention.

Methods

The serum proteome of patients with PsA and RA was interrogated using liquid chromatography mass spectrometry (LC-MS/MS) (n=64 patients), a multiplexed antibody assay (Luminex) for 48 proteins (n=64 patients) and an aptamer-based assay (SOMAscan) targeting 1,129 proteins (n=36 patients). Multiple reaction monitoring assays were developed to evaluate the performance of putative markers in the discovery cohort (n=60) as well as an independent cohort of PsA and RA patients (n=167).

Results

Multivariate analysis of the protein discovery data revealed that it was possible to discriminate PsA from RA patients with an area under the curve (AUC) of 0.94 for nLCMS/MS, 0.69 for Luminex based measurements; 0.73 for SOMAscan analysis. Random forest models confirmed that a subset of protein measured by MRM could differentiate PsA and RA patients with an AUC of 0.79 and 0.85 during separate evaluation and verification studies.

Conclusion

We report a serum protein biomarker panel which can separate EIA patients with PsA from those with RA. We suggest that the routine use of such a panel in EIA patients will improve clinical decision making. With continued evaluation and refinement on additional and larger patient cohorts including those with other arthropathies we suggest the panel identified here will contribute toward improved clinical decision making.