Choosing the best treatment
Several medications appear to have greater efficacy in seropositive than seronegative RA patients. For example, a meta-analysis of four randomized trials including a collective 2,177 RA patients assigned 2:1 to rituximab (Rituxan) or placebo concluded that 75% of seropositive RA patients had a EULAR moderate or good response at week 24 on the biologic, compared with 44% of seronegative patients.
“Would you not use rituximab in someone who’s seronegative? No, I actually would use it. I may not rush to use it as much, maybe give it earlier in someone who’s seropositive, but I’ve used rituximab in seronegative patients who’ve done just fine,” according to Dr. Cush.
The published experience with abatacept (Orencia) is mixed, most of it coming from European observational datasets. On balance though, 80% of the articles addressing the issue have concluded that response rates to the biologic are better in seropositive RA, he continued.
Australian investigators who pooled data from five phase 3 randomized clinical trials of tofacitinib (Xeljanz) in RA concluded that double-positive patients – that is, those who were seropositive for both rheumatoid factor and anti–citrullinated protein antibody (ACPA) – were roughly twice as likely to achieve ACR20 and ACR50 responses to the oral Janus kinase inhibitor at either 5 or 10 mg twice daily than patients who were double negative.
“Double positivity is very important in prognosis and severity, compared to single positivity,” the rheumatologist observed. “I think you should worry most about the patients who have the highest titers of rheumatoid factor and ACPA.”
Asked about the merits of supplemental laboratory testing for serum 14-3-3 eta, a proposed novel biomarker in RA, as well as for anti–carbamylated protein antibodies (anti-CarP), Dr. Cush replied that it’s unclear that the additional testing is really worthwhile.
“Ordering more tests doesn’t make us smarter,” he commented. “Quite simply, with rheumatoid factor and ACPA, adding one on top of the other, you just gain maybe 10% more certainty in the diagnosis. Adding anti-CarP antibodies or serum 14-3-3 eta doesn’t add more than a few percentage points, but now you’ve quadrupled the cost of testing.”
Dr. Cush reported receiving research funding from and/or serving as a consultant to numerous pharmaceutical companies.