Background/Purpose:

Considerable
heterogeneity across clinical domains of psoriatic arthritis (PsA) can make
assessment of disease activity challenging. As a result, there has been
interest in developing biomarkers to assess disease activity. In rheumatoid
arthritis (RA), a multi-biomarker disease activity (MBDA) assay, a weighted
composite of 12 serum protein biomarkers, has been shown to correlate with
disease activity.¹ Our objective was to
investigate if the MBDA score and its biomarker panel correlated with disease
activity across different domains of PsA.

Methods:

A
cross-sectional sample of 30 adult patients with PsA fulfilling the CASPAR
criteria² was recruited from UCSD Arthritis Clinics. Clinical data
and serum samples were collected and serum was analyzed for MBDA score and its
individual components³, as well as intracellular adhesion molecule 1
(ICAM-1), interleukin 6 receptor (IL-6R), and macrophage-derived cytokine
(MDC).

Results:

The table shows patient characteristics:

The average
MBDA score was 39.6, which would be consistent with a moderate disease activity
score in RA patients.¹ In our PsA cohort,
the MBDA score was most strongly correlated with physician global assessment
(Pearson correlation coefficient, r=0.57), DAS28 (r=0.53), and skin BSA (r=0.50).
Correlations were poorer with CDAI (r=0.35), SJC28 (r=0.35), patient global
assessment (r=-0.08), HAQ score (r=0.15), and pain score (r=0.12). Analysis of
individual biomarkers showed strong correlations, in many cases stronger than
the composite MBDA score: e.g., serum amyloid A (SAA), tumor necrosis factor
receptor superfamily member 1A (TNF-RI), MDC, and leptin with skin BSA (r=0.85,
0.84, 0.75, 0.72, respectively); leptin and ICAM-1 with DAS28 score (r=0.62 and
0.52); and SAA and vascular cell adhesion molecule 1 (VCAM-1) with physician
global assessment (r=0.67 and 0.61).

Conclusion:

These data
suggest the MBDA score can correlate with facets of disease activity in PsA.
However, individual biomarkers were frequently found to correlate, often more
strongly, with different domains of disease activity raising the possibility
that specific composite scores could be created for each PsA domain. Whether
these serum biomarkers are modulated by therapy and associated with clinical
response warrants further study.

References:

1. Curtis JR, et al. Arthritis Care Res 2012; 64: 1794-1803

2. Taylor W, et al. Arthritis Rheum 2006; 54: 2665-2673

3. Eastman PS, et al. J Pharm Biomed Anal 2012; 70: 415-24