Serum pulmonary and activation‐regulated chemokine/CCL18 levels in patients with systemic sclerosis: A sensitive indicator of active pulmonary fibrosis

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Abstract
Objective: To clarify the clinical significance of serum levels of pulmonary and activation‐regulated chemokine (PARC) in the diagnosis and monitoring of pulmonary fibrosis (PF) in patients with systemic sclerosis (SSc) and to compare PARC levels with KL‐6 antigen or surfactant protein D (SP‐D) levels.Methods: Serum PARC levels were determined by enzyme‐linked immunosorbent assay in 123 SSc patients. In a retrospective longitudinal study, correlation of serum PARC levels with the activity of PF was assessed in 21 SSc patients with active PF.Results: PARC levels at the first visit were higher in patients with SSc than in patients with systemic lupus erythematosus (SLE) or healthy controls. Increased serum PARC levels were associated with involvement of PF, decreased diffusing capacity for carbon monoxide, and decreased vital capacity in SSc patients. In the longitudinal study, serum PARC levels were significantly decreased in SSc patients with inactive PF compared with those with active PF.Conclusion: Elevated serum PARC levels correlated with PF and more sensitively reflected the PF activity than did serum KL‐6 or SP‐D levels in SSc. Serum PARC levels may be a useful new serum marker for active PF in SSc.