Infliximab shows drastic efficacy for controlling
inflammation in
rheumatoid arthritis (RA), though the ideal dose of
infliximab to keep suppressing
inflammation has not yet been identified. Recently, it has been evidenced that the minimum trough serum
infliximab levels required for suppressing
inflammation are greater than 1 µg/mL. This cross-sectional study was designed to identify the minimum dosage of
infliximab for maintaining serum
infliximab levels greater than 1 µg/mL. Thirty seven RA patients were enrolled in this study and they were divided into two groups (high-
infliximab vs. low-
infliximab) in reference to Remi-check Q®, a kit for examining serum
infliximab levels above/below 1 µg/mL by LC.
Infliximab dosage (p=0.06) and dosage interval (p=0.05) had trends to have differences between groups. A formula calculated by
infliximab dosage divided by dosage interval and
body weight (mg/weeks/kg) was shown to have significantly higher levels among high-
infliximab group (p=0.04). Based on whether serum
infliximab levels above/below 1 µg/mL and values led by the equation,
infliximab dosage/
infliximab interval/
body weight (mg/weeks/kg), a receiver operating characteristic curve (ROC) was depicted with area under the ROC curve 0.750 and the cut-off point for the serum
infliximab levels greater than 1 µg/mL was identified as
infliximab dosage/
infliximab interval/
body weight ≧0.750 with the sensitivity 0.393 and the specificity 1.000. In conclusion, we identified that the minimum
infliximab dosage to maintain serum
infliximab levels greater than 1 µg/mL was
infliximab dose/dosage interval/
body weight (mg/weeks/kg)≥0.750.