Red flags for underlying PID
Recurrent infections are a hallmark of PIDs. And mutations that cause increased infections can alter central and peripheral tolerance, affecting cell growth, signaling, and survival, which in turn affects immunity.
“As we use biologics in our patients with rheumatologic diseases, I think there’s a cohort of patients we’re starting to identify who are getting very serious recurrent infections. It’s not every patient. But that patient who’s had three or four serious infections, that’s the patient who I think we’ll be able to identify in our clinics through an immunodeficiency evaluation. Likewise, the patients who are not responding to multiple different drugs, that’s where I’d stop and think about an underlying immune deficiency,” she said.
A show of hands indicated only about 25% of her audience of rheumatologists routinely ask new patients if they have a personal or family history of recurrent infections. That should be routine practice, in Dr. Postolova’s view. The 10 warning signs of PID for adults put forth by the Jeffrey Modell Foundation focus on a family or personal history of recurrent ear or sinus infections, deep skin abscesses, pneumonia, viral infections, persistent thrush, or chronic diarrhea with weight loss.
Testing for PID
It’s “absolutely appropriate” to start a work-up for suspected immunodeficiency in a rheumatology clinic, according to Dr. Postolova.
“I think every allergist/immunologist would be grateful if you can just order a quantitative immunoglobulin panel as well as specific antibody titer responses to tetanus, diphtheria, pneumococcal vaccine, and an IgG subclass analysis. That’s half of an immunologist’s initial assessment,” she said.
Corticosteroids and other disease-modifying antirheumatic drugs (DMARDs) affect flow cytometry test results. It’s best to hold off on testing until after a patient has been off therapy for 2-3 months. Similarly, treatment with intravenous immunoglobulin (IVIg) will confound measurement of vaccine antibody titers, so it’s recommended to wait for 3-6 months off IVIg before testing.
Genetic testing for PID has become a lot simpler and more affordable. Numerous companies have developed test kits featuring relatively small panels of selected genes of interest. Dr. Postolova often uses Invitae, a Bay Area company that has a 207-gene panel covered by most insurers with an out-of-pocket cost to the patient of $250.
“Upfront when I have a complicated patient where I am concerned about the possibility of immunodeficiency, I will ask if that’s something they can afford and if they want to move forward with it. Also, Invitae has a patient assistance program. I’ve found this helpful in some of my very complicated patients,” she said.
Get to know your local allergist/immunologist
Many allergist/immunologists have overcome their traditional reservations about immunosuppressing an immunosuppressed individual and are now treating PID/autoimmune disease–overlap patients with the very drugs rheumatologists use every day, including standard DMARDs, rituximab, abatacept, anakinra, and tumor necrosis factor inhibitors.
“I encourage you to work with your allergist/immunologist for these patients because they’re going to need help,” according to Dr. Postolova. “The people in this room are the most equipped to treat the overlap patients because allergists and immunologists don’t really have the training to use these drugs. A lot of them do use them, but you have a better handle on these drugs than other people.”
Dr. Postolova reported having no financial conflicts regarding her presentation.