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TNF drug levels & Anti-TNF drug neutralising antibodies (Infliximab, Adalimumab, Etanercept)

Category Immunology
Test background

A significant proportion of patients treated with anti-TNF therapy are primary non-responders and require dose- or dose frequency adjustments. The lack of response to treatment has also been attributed to immunogenicity and the development of anti-drug neutralising antibodies. Studies have shown that response rates increase with infliximab trough concentration and serum drug levels at 4 weeks post-infusion in some patients are positively correlated with duration of response. However the probability of an infection increases with the number of anti-TNF infusions. Anti-TNF drugs can therefore be considered to have a narrow therapeutic index and drug monitoring based on serum trough levels together with monitoring for anti-drug antibodies (neutralising antibodies) may improve clinical treatment decisions.

An in-house ELISA assay is used to measure serum trough drug levels. Neutralising antibodies are measured by luminescence with a TNF sensitive transfected cell line.

Clinical Indications

For the monitoring of patients treated with Infliximab, Adalimumab, or Etanercept. (Please note we can only measure neutralising antibodies when drug trough levels are below 1.2 µg/ml).

Reference range

Target trough levels for anti-TNF differ based on disease type, sampling time point (induction vs maintenance) and the target therapeutic outcome (e.g. clinical response vs endoscopic remission).

Sample & container required Serum (rust top RST tube)
Sample volume 5-10 mL blood (1 mL serum)
Sample collection

Perform venesection BEFORE next drug infusion

Turnaround time Drug levels = 2 weeks
Neutralising antibodies = 4 weeks