People with ANCA-associated vasculitis have about seven times the risk of developing an infection compared with individuals in the general population, a study found.
The study, “Characterizing infection in anti-neutrophil cytoplasmic antibody–associated vasculitis: results from a longitudinal, matched-cohort data linkage study,” was published in the journal Rheumatology.
ANCA-associated vasculitis (AAV) is an autoimmune disease that is caused by the production of self-reacting antibodies that wrongly target and attack neutrophils, a type of immune cell, damaging small blood vessels throughout the body.
Autoimmune diseases are normally treated with immunosuppressive therapy, which, as the name suggests, works by suppressing the activity of the immune system. However, a weakened immune system also makes AAV patients more susceptible to infections.
“Studies of infection in AAV report variable risks, ranging from 6% to 67%,” the researchers wrote. However, they added, “currently there is no ideal method for assessing infection risk in a patient population.”
In order to attain a thorough understanding of infection risk, the researchers said, it’s necessary to use various approaches that involve obtaining information from different levels of healthcare, including hospitalizations, microbiological lab records, and antibiotic prescriptions.
In Scotland, population-based healthcare records are routinely collected electronically. A group of researchers in the U.K. took advantage of this extensive, centralized dataset to conduct a study to evaluate infection rates in AAV patients compared with the general population. In addition to infection rates, investigators also characterized the types of infections (severity and disease-causing microbes) found in AAV patients.
The study included data from 379 AAV patients and 1,859 controls, who were followed for a median of 3.5 years.
During follow-up, more than half (55.4%) of AAV patients had least one laboratory-confirmed infection, whereas only 15.8% of individuals from the general population experienced the same outcome. This placed AAV patients at a 7.3-fold higher risk of developing an infection compared with controls.
Researchers found that approximately a third (35.6%) of AAV patients had at least one severe infection during follow-up, while only 10.9% of individuals from the general population did. This put AAV patients at a 4.4 times higher risk of having a severe infection compared with the control population.
They also found the percentage of AAV patients who were prescribed antibiotics during follow-up was much higher compared with the general population (74.6%, versus 53%). In other words, those with AAV had a 2.2-fold higher chance of receiving an antibiotic prescription.
Trend analysis showed that AAV patients had the highest rates of infections during the first year of follow-up, particularly in the first 30 days.
While the rates of laboratory-confirmed infections and severe infections dropped after one year of follow-up, AAV patients continued to be at a higher risk of experiencing both compared to controls throughout the entire follow-up period.
Bacteria from the Escherichia genus were the most commonly identified disease-causing microbes in both AAV patients (16.6%) and controls (5.5%).
However, the greatest disparity was found for infections caused by different herpes viruses, which were found to be 12.5 times more prevalent in AAV patients than in controls. This was followed by infections caused by the yeast Candida, which were 11.4 times more common in AAV patients.
“AAV patients have up to seven times higher risk of infection than the general population, and the overall risk remains significant after eight years of follow-up,” investigators wrote.
Since the risk of infection remains higher than in the general population — even after eight years — researchers suggested that AAV patients be administered broad-spectrum antibiotics, at least during the first months.