Correction: Serum matrix metalloproteinase 3 levels are associated with an effect of iguratimod as add-on therapy to biological DMARDs in patients with rheumatoid arthritis.

[This corrects the article DOI: 10.1371/journal.pone.0202601.].

There is an error in the second sentence of the Subjects and Methods section. The correct sentence is: This was defined as the state of 2.6 < DAS28ESR < 5.1 or PD score ≥ 2 in at least one of the 28 joints on US examination.

There is an error in the fourth sentence of the fifth paragraph of the Discussion section. The correct sentence is: Therefore, the effects of bDMARDs on the serum MMP-3 levels could not be evaluated accurately.

There is an error in the first sentence of the eighth paragraph of the Discussion section. The correct sentence is: According to a report by Hattori et al. analyzing 114 RA patients treated with adalimumab for 52 weeks or longer, the rate of improvement of the serum MMP-3 levels after 4 weeks was significantly higher in the DAS28-CRP remission group.

In Fig 3, the headings PSL using and PSL non-using are swapped. The left side should be PSL non-using and the right should be PSL using. Please see the corrected Fig 3 here.

Fig 3

Comparison of the serum MMP-3 levels at 12 weeks and the MMP-3 ratio between steroids using and non-using groups (A). Correlation between the serum MMP-3 levels at 12 weeks / the MMP-3 ratio and dosage of steroids (B). MMP-3 ratio, ratio of the serum matrix metalloproteinase 3 levels at baseline to those at 12 weeks; PSL, prednisolone.