The researchers found that infection risk was not significantly higher in patients who stayed on their medication.

But Tim Bongartz, MD, associate professor of rheumatology at Mayo Clinic in Rochester, Minn., finds several problems in the study as initially presented (the study has not yet been published, so he did not have access to the details). “I’m extremely doubtful that we can draw any meaningful conclusions with respect to clinical practice out of this,” says Dr. Bongartz.

One problem is that the study doesn’t differentiate among different RA drugs. “It’s a huge issue to just lump all the agents together. There might be agents that increase the risk, there might be agents that decrease the risk, and then you come up with a summary estimate that may not show any effect,” he says. To date, says Dr. Bongartz, there is little convincing evidence that standard DMARDs (such as methotrexate) increase the risk of post-surgical infection, but the biologic drugs known as TNF inhibitors are usually discontinued because the majority of the evidence points to an increased infection risk. Major studies have not been conducted using other types of biologics, he notes, for example interleukin-1 or interleukin-6 inhibitors.

The study also lumped together many different kinds of surgeries, all of which have different inherent infection risks, says Dr. Bongartz. And the method the researchers used to estimate when the drug was stopped prior to surgery doesn’t take into account the different “half lives” of RA drugs, some of which take much longer to leave the body than others.

Those are all issues Dr. Ng and his colleagues say they hope to address in future research. “Our results grouped all types of surgeries and different DMARDs/[biologic agents],” they note. “Further analyses looking at different types of surgeries and individual DMARDs/[biologic agents] will be helpful to evaluate possible differences in infection risks between individual DMARDs/[biologic agents] in different types of surgeries.”