Spondyloarthritis & psoriatic arthritis
Serum calprotectin and complement factor C3 are superior biomarkers of inflammation in early psoriatic arthritis as compared with C-reactive protein
Authors' conclusion
C3 and calprotectin are elevated in early PsA and are responsive to treatment. These markers outperform CRP in obese and CRP-negative patients
Study context
- Population
- Adults with early, treatment-naïve psoriatic arthritis (PsA), compared with early rheumatoid arthritis (RA) and healthy controls
- Participants
- 67 / 50 / 61
- Exposure
- Early PsA vs early RA vs healthy controls (HCs)
- PsAn = 67
- RAn = 50
- HCn = 61reference
- Outcome
- Alternative biomarkers of inflammation (C3, S100A8/9, SAA) in early PsA
- Follow-up
- Baseline
Methodological detailsmulticentre
- Multicentre
Main finding
As reported in the abstract
Median serum C3 and S100A8/9 levels
| Group | Value | S100A8/9 median |
|---|---|---|
| PsA | median 1.38 g/L | 5.58 µg/mL |
PsA
Valuemedian 1.38 g/L
S100A8/9 median5.58 µg/mL
Observational data: associations, not effects.
Further findings
C3 and S100A8/9 in 'C reactive protein (CRP)-negative' subgroup · baseline
- C3 and S100A8/9 increased in PsA vs HC
Biomarkers in obese subgroup · baseline
- CRP did not discriminate PsA, RA and HC
- S100A8/9 significantly increased in PsA and RA vs HC
- Serum amyloid A (SAA) and derived inflammatory ratios (neutrophil/monocyte, lymphocyte/monocyte) did not discriminate PsA, RA or HC
Change in C3 and S100A8/9 in PsA achieving low disease activity · 1 year
- C3 and S100A8/9 decreased significantly
Diagnostic performance of composite C3×calprotectin vs CRP, obese subgroup
- C3×calprotectin AUC, superior to CRP
- 0.836
Original publication
Serum calprotectin and complement factor C3 are superior biomarkers of inflammation in early psoriatic arthritis as compared with C-reactive protein. RMD Open. Published 23 September 2025. doi:10.
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