Table 1.
Baseline characteristics
| Characteristic | Patients stable on any IFN beta therapy | Patients stable on IM IFN beta-1a therapy | ||||||
|---|---|---|---|---|---|---|---|---|
| Before matching | After matching | Before matching | After matching | |||||
| No switch (n = 11,488) | Switch (n = 188) | No switch (n = 531) | Switch (n = 177) | No switch (n = 5673) | Switch (n = 93) | No switch (n = 270) | Switch (n = 90) | |
| Age, mean (SD), years | 49.3a (9.2) | 46.3a (9.9) | 47.5 (9.9) | 46.9 (9.6) | 50.4 (8.8) | 46.0a (10.1) | 47.3 (9.9) | 46.5 (9.9) |
| Female, % | 75.8 | 77.1a | 78.5 | 78.5 | 78.0 | 79.6 | 80.0 | 80.0 |
| Baseline treatment, % | ||||||||
| IM IFN beta 1a (Avonex®) | 49.4 | 49.5 | 50.8 | 50.8 | 100.0 | 100.0 | 100.0 | 100.0 |
| SC IFN beta 1a (Rebif®) | 31.6 | 24.5 | 24.9 | 24.9 | – | – | – | – |
| SC IFN beta 1b (Betaseron®) | 19.0 | 26.1 | 24.3 | 24.3 | – | – | – | – |
| Any inpatient stays at baseline, % | 3.3 | 4.3 | 3.8 | 4.0 | 3.4 | 3.2 | 3.3 | 2.2 |
| Any ER visits at baseline, % | 13.9 | 15.4 | 15.6 | 15.3 | 13.6 | 11.8 | 12.2 | 11.1 |
| Charlson comorbidity index, % | ||||||||
| 0 | 78.5 | 77.7 | 76.1 | 78.5 | 78.6 | 79.6 | 77.4 | 81.0 |
| 1 | 8.1 | 6.9 | 8.5 | 7.3 | 8.0 | 6.5 | 8.5 | 7.0 |
| 2 | 9.7 | 11.2 | 12.1 | 9.6 | 9.5 | 12.9 | 9.6 | 11.0 |
| 3+ | 3.7 | 4.3 | 3.4 | 4.5 | 3.9 | 1.1 | 4.4 | 1.0 |
| Interval between last pill access and index date, mean, days | 9.1 | 14.3 | 15.3 | 20.5 | 7.5 | 11.3 | 10.3 | 17.1 |
For the IM IFN beta-1a therapy group, the three patients that were unmatched were significantly younger than the matched population
ER emergency room, IFN interferon, IM intramuscular, SC subcutaneous, SD standard deviation
aP < 0.05 versus no-switch group