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 using the ILite NAb bioassay (BioMonitor) which detects antibodies in serum with the ability to neutralise anti-TNF drugs.
For the monitoring of patients treated with Infliximab, Adalimumab, or Etanercept. (Please note we will only measure neutralising antibodies when drug trough levels are below 0.5ug/ml).
Serum - RST (rust top gel)
Perform venesection BEFORE next drug infusion
Drug levels = 2 weeks
Neutralising antibodies = 4 weeks