Risk for opportunistic infection among MS patients.

Patients with multiple sclerosis (MS) are at increased risk for most types of infection, with the highest risk associated with renal tract infections, according to an analysis of USA Department of Defense data.

Susan Jick, DSc, director of the Boston Collaborative Drug Surveillance Program and professor of epidemiology and biostatistics at Boston University, and colleagues sought to understand the rates at which infections occur because they are known to be a common cause of comorbidity and death in patients with MS.

Jick and colleagues presented rates of infection in patients with MS after MS diagnosis, compared with a matched population of patients without MS.

The MS cohort included patients who had MS diagnosed and treated between January 2004 and August 2017. Patients had medical history available for at least 1 year before MS diagnosis and at least one prescription for an MS disease-modifying treatment.

Patients without MS were matched 10:1 to patients with MS based on age, sex, geographic region, and cohort entry date. For each patient, the researchers identified the first diagnosed infection of each type after cohort entry. They followed patients until loss of eligibility, death, or end of data collection.

In all, the study included 8,695 patients with MS and 86,934 matched patients without MS.

After cohort entry, the incidence rate (IR) of any infection was higher among patients with MS, compared with non-MS patients (4,805 vs 2,731 per 10,000 person-years; IR ratio, 1.76). In addition, the IR of hospitalized infection was higher among MS patients (125 vs. 51.3 per 10,000 person-years; IRR, 2.43).

In both cohorts, females had a higher risk of infection than males did. The rate of renal tract infection was more than fourfold higher among females, compared with males, in both cohorts. Relative to non-MS patients, however, men with MS had a higher IRR for renal tract infection than women with MS did (2.47 vs. 1.90).

The risk for any opportunistic infection was slightly increased among MS patients.