Background Infection is a critical complication that occurs during the management of RA patients. High levels of serum C-reactive protein (CRP), is not easily distinguishable between the exacerbations of RA from infections. PTX3 is a novel biomarker which responds to local inflammation. The following study evaluates the diagnostic use of PTX3 in RA patients with high levels of CRP.
Objectives To evaluate the diagnostic use of PTX3 in RA patients with high levels of CRP.
Methods 18 RA patients with infections (infection RA: iRA), 20 with high disease activity of RA (flare RA: fRA) and 23 healthy controls (HC) were enrolled in this study.
Patients whom pathogens were identified were designated as iRA (15 bacterial, 2 viral and 1 mycosis).
We measured PTX3, CRP, procalcitonin (PCT) and neutrophil CD64 (nCD64), pre- and post-treatments (iRA and fRA) and at any time (HC).
PTX3 levels were measured using an enzyme-linked immunoabsorbent assay (ELISA). mCD64 was measured by a quantitative flow cytometry using fluorescene microbeads.
Levels of respective measurements at both pre- and post-treatment were analyzed using the Wilcoxon signed-rank test, and comparisons of levels within each group were analyzed using the Mann-Whitney's U-test.
Results At pre-treatment, levels of PTX3 in iRA (15.1±20.7 ng/ml) are significantly higher compared with those in fRA (3.6±4.2 ng/ml). Both levels for iRA and fRA were significantly higher compared with those in HC (0.89±0.91 ng/ml). Additionally, levels of PCT (0.048±0.042 ng/ml) and nCD64 (1488±470 molecules per cell) at pre-treatment in fRA were <0.5 ng/ml and <2,000 molecules per cell, respectively.
After treatment, levels of PTX3 (p<0.01), CRP (p<0.01), PCT (p<0.01), nCD64 (p<0.01) were significantly decreased in iRA. In fRA, CRP (p<0.01), PCT (p<0.01), nCD64 (p=0.02) were significantly decreased after treatment, but PTX3 levels were not (p=0.13).
Conclusions Plasma PTX3 levels may be a helpful tool in distinguishing worsening of RA from complications due to infection.
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J Rheumatol. 2012; 39:1517-23
Disclosure of Interest None declared
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