Background/Purpose : Triggering receptor expressed on myeloid cells-1 (TREM-1) is a cell-surface receptor, expressed mainly on monocytes and neutrophils and involved in amplification of the inflammatory response. Previous studies have shown an upregulation of TREM-1 in synovium of patients with rheumatoid arthritis (RA) as well as increased levels of soluble TREM-1 (sTREM-1) in synovial fluid and blood of patients and animal model of RA. We sought to determine the serum sTREM-1 levels in disease-modifying anti-rheumatic drug (DMARD)–naïve early rheumatoid arthritis (ERA), to investigate the association of sTREM-1 levels with Disease Activity Score in 28 joints (DAS28) and seropositivity for anti- cyclic citrullinated peptide (CCP) antibody, and to determine the predictive value of sTREM-1with respect to clinical response to DMARD therapy. 

Methods : Twenty-two consecutive patients with DMARD-naïve ERA were prospectively evaluated for serum sTREM-1 by means of ELISA at diagnosis and at the following clinic visit after low dose prednisone and/or DMARD have been administered, and related to DAS28 and  serum level of anti-CCP  Ab’. We compared the sTREM-1 level to that of 31 patients with established RA as well as to 24 controls.

Results : Serum sTREM-1 level was significantly higher in the DMARD-naïve ERA group (2,122.9±388.9 ρg/ml) compared to established RA group (1,478.0±280.0 ρg/ml, p = 0.001) and normal control (34.4±7.4 ρg/ml, p < 0.001). In the ERA group, elevated basal sTREM-1 level was significantly associated with DAS28-CRP (p = 0.001, HR3.23, 95% CI 1.4 – 8.12), DAS28-ESR (p = 0.04, HR 2.34 95%CI 0.1-8.12), as well as predicted higher DAS28 at the following encounter after DMARD treatment was administered (p = 0.001, HR 3.2 95% CI 1.1-7.2), as well as in patients with established RA. Higher serum sTREM-1levels were significantly associated with higher titers of anti-CCP antibody (p < 0.001).

Conclusion : Our results suggest that serum sTREM-1 may provide a novel biomarker of DMARD-naïve ERA as well as of disease activity and seropositivity for anti-CCP antibody in RA.