Table 1.
Demographic and clinical characteristics of patients.
| Total study population (n = 42) | No detectable Ifx levels (n = 20) | Low Ifx levels (n = 13) | High Ifx levels (n = 9) | |
|---|---|---|---|---|
| Age at onset (years), mean ± SD | 57.1 ± 14.0 | 49.6 ± 14.5 | 61.6 ± 10.8 | 67.4 ± 6.1 |
| Female, n (%) | 37 (88.1) | 19 (95) | 9 (69.2) | 9 (100) |
| Disease duration (years), mean ± SD | 19.4 ± 10.4 | 16.3 ± 6.3 | 17.9 ± 10.1 | 28.3 ± 13.8 |
| Duration of Ifx treatment (years), median (IQR) | 6.2 (1–13) | 4.25 (1.23–8.63) | 6.25 (4.38–10.75) | 8.25 (8.25–10.25) |
| ACPA-positive, n (%) | 36 (85.7) | 19 (95) | 12 (92.3) | 5 (55.6) |
| RF-positive, n (%) | 35 (83.3) | 18 (90) | 10 (76.9) | 7 (77.8) |
| Methotrexate therapy, n (%) | 36 (85.7) | 16 (80) | 12 (92.3) | 8 (88.8) |
| Methotrexate dose (mg/week), median (IQR) | 12.5 (0–25) | 15.0 (0–15) | 15 (0–20) | 10 (0–15) |
| Other DMARDs, n (%) | 18 (42.9) | 9 (21.4) | 4 (9.2) | 5 (11.9) |
| Concomitant use of glucocorticoids, n (%) | 28 (66.6) | 13 (30.9) | 8 (19) | 7 (16.6) |
| Prednisone dose (mg/day) before Ifx increase, mean ± SD | 6.2 ± 5.2 | 5.7 ± 6.8 | 4.2 ± 3.2 | 7.0 ± 6.4 |
| Prednisone dose (mg/day) at one year, mean ± SD | 7.9 ± 6.3 | 8.7 ± 7.6 | 7.1 ± 6.3 | 8.2 ± 5.6 |
| DAS28 at the start Ifx treatment, mean ± SD | 5.50 ± 1.20 | 5.68 ± 1.29 | 5.03 ± 1.04 | 5.77 ± 1.12 |
| Baseline DAS28 before Ifx increase, mean ± SD | 4.55 ± 1.01 | 4.91 ± 0.73 | 3.72 ± 0.90 | 4.97 ± 1.06 |
| Trough Ifx levels before dose increase (μg/mL), median (IQR) | 94.5 (0–10.5) | ND | 574 (16–1024) | 2112 (1152–10464) |
| ATI levels before Ifx increase, AU/mL, median (IQR) | 0 (0–60000) | 1068.5 (377.5–12328.0) | 0 (0–0) | ND |
Ifx, Infliximab; SD, standard deviation; IQR, interquartile range; ACPA, anti-citrullinated peptide antibodies; RF, rheumatoid factor; DMARDs, disease-modifying anti-rheumatic drugs; DAS28, disease activity score in 28 joints; ATI, anti-infliximab antibodies; AU/mL, arbitrary units per milliliter; ND, not detectable.