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.