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We thank Sanmarti et al1 for their interest in our study2 and the confirmation of our results in Caucasian patients with rheumatoid arthritis (RA). We agree that monitoring of serum drug trough levels would help to optimise anti-tumor necrosis factor (TNF)-α therapy for patients with RA in clinical practice.
The serum drug trough levels in our patients with RA who showed good therapeutic response were very close to those observed by Sanmarti et al,1 possibly reflecting a similar status in pharmacokinetics in different ethnic populations. However, the drug trough levels may vary with different detection methods, dosing and timing of the used drug or concomitant disease-modifying antirheumatic drugs2–4 and may be further complicated by the presence of antidrug antibodies.5
Although not yet addressed in the updated 2013 European League Against Rheumatism recommendation,6 the determination of drug trough levels would be a valuable guide for clinicians to optimise dosing of biologics according to a personalised treatment algorithm2 3 ,7 and avoid overtreatment for patients with RA receiving anti-TNF-α therapy.2 3 ,8 For example, Pouw et al3 have identified the therapeutic range of adalimumab trough levels at 5–8 μg/mL for maximal clinical response, providing a useful reference for downtitration of adalimumab dose. However, the optimal cut-off trough levels of adalimumab and etanercept which can predict a good therapeutic response in patients with RA should still be validated in longitudinal and larger scale studies.
Contributors All authors made substantive intellectual contributions to the present response and approved the final manuscript. Y-MC drafted the manuscript and D-YC drafted and revised the manuscript.
Competing interests None.
Provenance and peer review Commissioned; internally peer reviewed.