OBJECTIVE: The aim of this longitudinal study was to examine the clinical significance of soluble lectin-like oxidized low-density lipoprotein receptor 1 (sLOX-1) in patients with rheumatoid arthritis. METHODS: We collected demographic and clinical data for a large rheumatoid arthritis cohort at 3 time points. Blood samples were collected at each time point; the number of samples was 282 cases in 2012, 431 cases in 2013, and 500 cases in 2014. Plasma sLOX-1 was measured by enzyme-linked immunosorbent assay. Correlations between sLOX-1 and clinical data were analyzed. Predictive factors associated with changes in sLOX-1 and rheumatoid factor (RF) were analyzed by multivariate linear regression. RESULTS: Plasma sLOX-1 level was significantly correlated with RF titer and other clinical parameters. The longitudinal analyses showed that changes in sLOX-1 were significantly correlated with changes in RF titers and with those at baseline. Multivariate linear regression analysis revealed that changes in RF and baseline RF were predictive factors for changes in sLOX-1. Conversely, the changes in RF were significantly correlated with the changes in sLOX-1 in all years. A stepwise regression analysis showed that the change in sLOX-1 was a predictive factor for the change in RF. CONCLUSIONS: The change in sLOX-1 has predictive value for assessing the change in RF, indicating the usefulness of sLOX-1 in clinical practice.