Real-World Study Shows MS Patients Have High Infection Risks

Outpatient claims and inpatient hospitalizations for infections — especially urinary and kidney infections — were higher among people with multiple sclerosis (MS) than controls, a large retrospective study of commercial insurance records showed.

MS patients were more than four times as likely to be hospitalized with urinary and kidney infections as others, reported Riley Bove, MD, of the Weill Institute for Neurosciences at the University of California San Francisco.

They also had nearly twice the risk of outpatient urinary and kidney infections, Bove said at ACTRIMS Forum 2021, the annual meeting of the Americas Committee for Treatment and Research in Multiple Sclerosis.

Few population-level risk estimates for specific categories of infections in MS patients exist in the U.S., she noted.

“These findings, from a modern U.S.-based cohort, support an elevated risk for a number of infection types in patients with MS,” Bove said. “Specifically, the elevated risk of urinary and kidney infections points to a need for better screening and management of bladder function,” she told MedPage Today.

The study evaluated relative risks for outpatient claims and inpatient hospitalizations for specific infections among 87,755 patients with MS and 87,755 control patients, using information from the IQVIA Real World Data adjudicated claims database from January 2010 through June 2019.

Participants in the MS cohort had two or more MS diagnoses 30 or more days apart; controls had two diagnoses for any other condition more than 30 or more days apart. The index date was a randomly selected office visit. All participants had no antibiotic or antiviral claims 60 days before the index date and no claims for pregnancy, inpatient residential care or end-stage renal disease facility, HIV, or HCV.

Baseline characteristics were matched exactly between the groups. Mean age was about 47 and 75.7% in each cohort were female. Nearly two-thirds in both groups (65.7%) had commercial insurance and one-third (34.3%) had self-insured employer insurance.

Urinary and kidney infections were the most frequent inpatient diagnoses for MS patients at 1.6%, followed by pneumonia and influenza at 0.77%, and skin infections at 0.57%. For outpatient diagnoses, other respiratory and throat infections topped the MS list at 30.31%, followed by urinary and kidney infections at 14.23% and viral infections at 6.83%.

Compared with controls, MS patients had a higher relative risk of inpatient hospitalizations for the following infections:

• Urinary/kidney: RR 4.49 (P<0.0001)
• Pneumonia/influenza: RR 2.22 (P<0.0001)
• Skin: RR 1.95 (P<0.0001)
• Other respiratory/throat: RR 2.37 (P<0.0001)
• Fungal: RR 3.69 (P<0.0001)
• Viral: RR 2.58 (P<0.0001)
• Opportunistic: RR 1.94 (P=0.0024)

Opportunistic infections included pneumocystis pneumonia, cryptosporidiosis, mycobacteria, bartonellosis, other mycoses, cryptococcosis, cytomegaloviral disease, human papillomavirus, other viral hepatitis, progressive multifocal leukoencephalopathy, Epstein-Barr virus, histoplasmosis, toxoplasmosis, and Legionella.

For outpatient diagnoses, MS patients had a higher relative risk of infections that were:

• Other respiratory/throat: RR 1.01 (P=0.24)
• Urinary/kidney: RR 1.82 (P<0.0001)
• Viral: RR 1.19 (P<0.0001)
• Fungal: RR 1.29 (P<0.0001)
• Skin: RR 1.26 (P<0.0001)
• Pneumonia/influenza: RR 1.16 (P<0.0001)
• Opportunistic: RR 1.50 (P<0.0001)

“We weren’t able to go into details about the potential mechanisms for our findings,” Bove said. But two main pathways could contribute to the higher risk of urinary and kidney infections, she noted.

“The first is use of immune-suppressing or modulating drugs. For example, some of the treatments for MS can result in lymphopenia or hypogammaglobulinemia, which could influence risk of infections,” she pointed out.

“The second is that MS, despite being a nervous system disease, can result in decreased function in other organs,” Bove continued. “For example, by causing neurogenic bladder retention, MS can increase the risk of urinary tract infections. Certainly, indwelling catheters could increase this risk.”

“We also know that patients with poorer health due to MS can face many barriers to care and wellness, and some may be less likely to see their primary care clinicians and to receive normal screening care,” she added.

Patients in the study had commercial health insurance, and findings may not apply to other groups, Bove noted. In addition, “we could not adjust for MS disability levels,” she said.