Forty-two patients with RA (35 women and 7 men, median age 46.8 years [range 20–67 years], disease duration 9.0 years [range 1–31 years]), diagnosed according to the revised criteria of the American College of Rheumatology (ACR) [
7], were enrolled. Rheumatoid factor was present in 31 of the patients. All received infliximab according to the ATTRACT (Anti-TNF Trial in RA with Concomitant Therapy) protocol at 3 mg/kg every 8 weeks, combined with methotrexate [
8]. The following indices were measured: tender joint count, swollen joint count, patient's assessment of pain, patient's global assessment of disease activity, physician's global assessment of disease activity, the Disability Index of the Health Assessment Questionnaire, serum levels of C-reactive protein and erythrocyte sedimentation rate. ACR response was recorded at 54 weeks [
9]. RA patients were divided into two groups: good responders, with an ACR response equal to or greater than 50 (
n = 24); and poor responders, with an ACR response equal to or less than 20 (
n = 18). EDTA-treated venous blood was collected before infliximab therapy in all patients (
n = 42). In 20 patients, blood samples were collected during infliximab treatment before and 4 hours after the first and ninth infusions. Plasma samples obtained by centrifugation were stored at -20°C and thawed before use. The main characteristics of the patients are summarized in Table
1.
Table 1
Patient characteristics
Age (years) | 46.81 ± 10.78 | 48.05 ± 9.47 | 0.51 |
Sex (% female) | 83 ± 11.27 | 70 ± 20.08 | 0.38 |
Disease duration (years) | 8.98 ± 8.39 | 8.80 ± 8.01 | 0.82 |
Previous DMARD treatment (n) | 2.78 ± 1.41 | 2.70 ± 2.70 | 0.47 |
Swollen joint count (0–28) | 4.57 ± 3.16 | 4.55 ± 2.70 | 0.43 |
Tender joint count (0–28) | 9.21 ± 5.78 | 8.35 ± 6.07 | 0.80 |
DAS28 score | 5.33 ± 1.12 | 5.31 ± 1.19 | 0.76 |
ESR (mm/hour) | 37.59 ± 23.18 | 37.45 ± 23.71 | 0.91 |
CRP (mg/l) | 26.93 ± 24.87 | 31.30 ± 27.24 | 0.65 |