Fall and winter are more than just seasons for chilly weather and festive holidays. This time of year is cold and flu season, with infection rates rising in October and peaking in January, according to the Centers for Disease Control and Prevention. People with autoimmune diseases like rheumatoid arthritis are at higher risk for developing both bacterial and viral infections. Likewise, researchers are trying to find ways to predict which patients may be most susceptible.

This higher susceptibility in people with RA is due to both their malfunctioning immune system, which is focused more on attacking the body’s healthy joints than fighting off invading particles, and the immunosuppressant drugs that most people with RA take to control the disease process, says Eric Matteson, MD, chair of rheumatology at the Mayo Clinic in Rochester, Minn.

“When you have rheumatoid arthritis, which is a serious disease, you need to have treatment for it. Even if that treatment carries risks of infection, people still do better with treatment than without it. So we thought, what can we do to predict who is at higher risk?” says Dr. Matteson.

He and three colleagues explored all the factors that play into a person’s risk of acquiring cold, flu or pneumonia, or even urinary-tract infections which are less seasonal. They then developed a score so physicians can know which patients have the highest susceptibility. Their findings were published in the September 2012 issue of the medical journal Arthritis & Rheumatism.

“We looked at different variables, and looked at the characteristics of people with RA that seem to play a role in infection risk,” he says. These include:

• Age
• Corticosteroid use (greater than 10 milligrams of prednisone a day)
• Disease activity as measured by tests like sedimentation rate, or RA that is not well controlled by drug treatments
• Presence of RA complications such as vasculitis or lung disease
• Presence of serous comorbidities like diabetes, alcoholism or emphysema

“So these are traditional things we think about when we look at infection risk, and things that are RA-specific,” says Dr. Matteson. “These coexisting conditions really identify if a person is at especially high risk of infection.”

The RA infection risk formula is complicated and cannot be calculated yet in an office or clinical setting, he adds. However, the data may help doctors determine which patients may be good candidates for clinical drug trials for RA, he says.
 

In addition to the new infection risk formula, researchers at Wake Forest Baptist Medical Center in Winston-Salem, N.C., are looking at other characteristics that affect an RA patient’s infection risk. Karen Haas, PhD, assistant professor of microbiology and immunology is conducting a study on how low levels of a key protein, C4, may affect the risk of infection with the Streptococcus pneumoniae bacterium, even in those who are vaccinated. This bacterium can be dangerous for people with RA or lupus. If inhaled from the air, the bacterium can cause respiratory pneumonia. If it gets into the person’s blood stream, it can cause a serious septic infection, says Haas.

C4 is one important element of increased susceptibility to infection in people with autoimmune diseases, says Haas. People with autoimmune diseases like systemic lupus erythematosus, for example, may show low levels of the protein during bad flares, she says.

The mice in the Wake Forest study were vaccinated against S. pneumoniae just like many humans with RA, says Haas. “Mice with low levels of C4 had a good antibody response to the vaccine,” she says.

The mice were then exposed to the bacterium either through the respiratory tract or through their bloodstream. In initial observations, the vaccinated mice fought off the dangerous blood infection.

“We had thought that the vaccine had to work with C4 to produce antibodies,” but that may not be the case according to this early research, says Haas. “Then we gave S. pneumoniae to them through the nose, the typical way we’d pick up bacteria. The vaccine did not protect them. They got very bad cases of pneumonia.”

So people with RA may still be at higher risk of bacterial infections even if they are vaccinated, this preliminary research seems to suggest. “Even though you are getting vaccinated, and you are getting a good antibody response, if you have low levels of C4, you may be deficient in your defense against lung bacteria,” says Haas. This study, funded in part by the Arthritis Foundation, is still in its early stages, so it’s unclear how C4 may play a role in the infection risk of people with RA who are vaccinated.

At this time, physicians recommend that people with RA get annual vaccinations and use preventive measures like regular hand washing or avoiding other people with infections if possible, says Dr. Matteson.

“If you have RA, your infection risk is double anyway, so it is really important to have identified those characteristics that the patient has, and to tell them that they have to take particular care if they are running a fever, have a cough, or have a burning sensation when they urinate,” says Dr. Matteson.

RA patients with any of these symptoms of infection should contact their health-care professional right away for treatment, he adds.