Characteristics of individuals with SLE initiating hydroxychloroquine and disease-modifying drugs after start of follow-up*, incidence rates of serious infections and HR with 95% CI comparing DMARD initiators with hydroxychloroquine initiators
| Hydroxychloroquine initiators | DMARD initiators | |
| N | 392 | 387 |
| Age, mean (SD) | 46.7 (17.4) | 45.9 (18.1) |
| Female, % | 87.5% | 80.1% |
| Years since SLE index date*, median (IQR) | 0.10 (0.01, 0.75) | 0.41 (0.09, 1.06) |
| History of nephritis | 15.6% | 39.5% |
| History of serious infection <1 year before start | 7.7% | 12.4% |
| Corticosteroid dispensation <6 months before start | 44.4% | 74.7% |
| Intravenous drug procedure code <6 months before start | 6.9% | 23.3% |
| Serious infections/person-years | 45 cases/1396 person-years | 94 cases/1665 person-years |
| Incidence rate (95% CI) per 1000 person-years | 32.2 (24.1 to 43.2) | 56.5 (46.1 to 69.1) |
| HR (95% CI) age-adjusted and sex-adjusted | 1.0 (reference) | 1.82 (1.27 to 2.60) |
| HR (95% CI) adjusted for nephritis, corticosteroids, history of infusion, history of infection | 1.0 (reference) | 1.30 (0.86 to 1.95) |
*Start of follow-up was when inclusion criteria were met (≥2 ICD coded visits with ≥1 ICD code from a specialist).
DMARD, disease-modifying antirheumatic drug; ICD, International Classification of Diseases.