A Large Case–Control Analysis
Previous studies have provided evidence for an MS prodrome that occurs years before a demyelinating event or the onset of clinical symptoms. Many of these studies, however, have been limited by a retrospective design or by the absence of a control group.
To analyze the question further, Dr. Tremlett and colleagues examined data from linked health administrative and clinical databases in the Canadian provinces of British Columbia, Saskatchewan, Manitoba, and Nova Scotia, which were chosen for their geographic diversity and comprehensive data. The researchers created a health administrative cohort, which was based on administrative data, and an MS clinic-derived cohort, which used administrative and clinical data. The study’s primary outcome was all-cause use of health care during each of the five years before the health administrative index date (ie, the first demyelinating disease-related claim) or clinical index date (ie, the date of MS symptom onset).
Health Care Use Increased in Prodromal MS
The health administrative cohort included 14,428 people with MS and 72,059 matched controls. In all, 10,525 (73%) of the patients with MS were women, and their mean age at the health administrative index date was 43. Compared with controls, annual health care use increased steadily between five years and one year before the first demyelinating disease claim in these patients.
The mean number of hospital admissions was 26% higher in people with MS than in controls in the fifth year before the index date, and 78% higher in the year before the index date. The mean number of physician claims was 24% higher in people with MS than in controls in the fifth year before the index date, and 88% higher in people with MS than in controls in the year before the index date. Also, the mean number of prescribed drug classes was 23% higher in people with MS than in matched controls in the fifth year before the index date, and 49% higher in people with MS than in controls in the year before the index date.
The MS clinic cohort included 3,202 people with MS and 16,006 matched controls. In all, 2,368 (74%) of people with MS were women, and the mean age at the clinical index date was approximately 37. Compared with the health administrative cohort, this cohort had similar patterns for physician claims and prescriptions, although the differences in use in each of the five years mostly did not reach statistical significance.
“To gain a better insight into the MS prodrome, the complex reasons for increased health care use will need to be established, for example, through access of additional administrative data such as the specific diagnostic codes related to a hospital admission or physician visit, or the therapeutic drug class for a prescription,” Dr. Tremlett concluded.
Wijnands JMA, Kingwell E, Zhu F, et al. Health-care use before a first demyelinating event suggestive of a multiple sclerosis prodrome: a matched cohort study. Lancet Neurol. 2017 Apr 20 [Epub ahead of print].