Clinical, demographic and laboratory features of 83 patients enrolled*
| All patients (n=83) | HCQ <100 ng/mL (n=24) | HCQ ≥100 ng/mL (n=59) | P value | |
| Sex, female | 79 (95) | 22 (92) | 57 (97) | 0.575 |
| Age, years mean±SD | 41±11 | 39±11 | 42±11 | 0.772 |
| Disease duration, years median (range) | 15 (2–37) | 17 (2–29) | 13 (2–37) | 0.692 |
| SLICC Damage Index median (range) | 0 (0–3) | 0 (0–1) | 0 (0–3) | 0.385 |
| Current smokers | 31 (37) | 9 (37) | 22 (38) | 0.816 |
| Body mass index (kg/m2) mean±SD | 25±5 | 24±4 | 26±5 | 0.828 |
| Estimated creatinine clearance, mL/min mean±SD | 89±24 | 94±22 | 86±24 | 0.129 |
| HCQ prescribed dose/weight (mg/kg) mean±SD | 5.3±1.2 | 5.4±1.2 | 5.4±1.2 | 0.71 |
| HCQ ng/mL median (range) | 327 (0–4003) | 0 (0–99) | 546.1 (101–4003) | <0.0001 |
| DCQ ng/mL median (range) | 47 (0–650) | 0 (0–11) | 79 (11–650) | <0.0001 |
| Additional treatment | ||||
| Immunosuppressors | 23 (28) | 13 (54) | 10 (17) | 0.001 |
| Azathioprine | 10 (12) | 5 (22) | 5 (8) | |
| Mycophenolate mofetil | 6 (7) | 3 (12) | 3 (5) | |
| Methotrexate | 5 (6) | 4 (17) | 1 (2) | |
| Ciclosporin | 2 (2) | 1 (4) | 1 (2) | |
| Glucocorticoids | 40 (48) | 11 (46) | 29 (52) | 0.974 |
*If not otherwise specified, the values are the number (%) of patients.
DCQ, whole blood concentration of desethylchloroquine; HCQ, whole blood concentration of hydroxychloroquine; SLICC, Systemic Lupus International Collaborating Clinics.