Background/Purpose: Serum RF was detected in 26-90% of RA patients, and high-titer RF has been shown a poor prognosis factor in RA and predictor of resistance to RA therapy. Several reports have shown that tumor necrosis factor (TNF) inhibitors decrease serum RF levels. However, it remains unclear whether changes in serum RF level during TNF inhibitors therapy reflects RA disease activity and predicts therapeutic response.

Methods: Subjects were 61 RA patients who filled ACR RA criteria 1987, were biologics-naïve, were treated with TNF inhibitors, and had moderate to high disease activity (DAS28-CRP≧2.7) and high titer of serum RF (≧100IU/ml). Their medical records were reviewed retrospectively. Serum RF titers were measured every visit t during TNF inhibitors treatment by using immunonephelometry, and more than 10% of changes in RF levels was judged as significantly. RA disease activity was measured by DAS28-CRP. Treatment responsiveness was assessed by EULAR response criteria.

Results: Subjects were 61 patients with 13 male and 48 female, 55.5 years (average) of age and 5.9 years (median) of disease duration. TNF inhibitors were 23 of infliximab, 32 of etenercept, 5 of adalmumab and 1 of golimumab. MTX were given to 40 patients with 7.7 mg (average) /week. At baseline serum RF levels were 386+415 U/ml (average +SD) and 221U/ml (median), and DAS28-CRP were 4.54 (average). Three months after TNF inhibitor therapy, RF titers were decreased in 87% of cases (347 at baseline and 135 U/ml at 3month, reduction rate; 61%), while 13% failed to reduce RF levels (751 at baseline and 830 U/ml Reduction rate; -10.5%). DAS28-CRP of patients without RF reduction (n=6) were 4.05 at baseline, 3.06 at 3 month at 3month and 2.83 at 12 month. Only 1 (17%) and 1 cases (17%) achieved clinical remission and low disease activity by DAS28-CRP at 12 month, and 2 cases (33%) satisfied good response by EULAR response criteria at 12 month. Among patients with RF reduction at 3month, 48% of cases showed re-elevation of RF titers (379 at baseline, 156 at 3month and 226 U/ml at 12 month) and others revealed continuous reduction of the titers (318 at base line, 117 at 3month and 63 U/ml at 12 month). DAS28-CRP of patients with RF re-elevation after 3month (n=26) were 4.58 at baseline, 2.80 at 3 month, 2.92 at 12 month. Among them clinical remission and low disease activity by DAS28-CRP were achieved in39% and 12%, respectively, and 46% of patients showed good response. DAS28-CRP of patients with RF continuous reduction (n=29) were 4.62 at baseline, 2.37 at 3 month, 2.08 at 12 month. Among them clinical remission and low disease activity by DAS28-CRP were achieved in 58% and 21%, respectively, and 79.3 % of patients showed good response, which was significantly high compared to those without RF reduction and those with re-elevation.

Conclusion: Three month after TNF inhibitors RF titers were reduced in 90% of patients. Those who failed decrease RF titers showed poor response to the therapy. Among patients with RF reduction at 3 month, 50% of them showed re-elevation of RF titers and others revealed continuous reduction of RF. Approximately 80% of patients with a continuous reduction of RF levels shows good response. Therefore, change in RF titers predicts therapeutic response of RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/change-in-rf-titers-reflects-ra-disease-activity-and-predicts-therapeutic-response-during-tnf-inhibitor-therapy-patients-with-a-continuous-reduction-of-serum-rf-levels-show-good-response/