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 |
| Notes | Please note, these tests are not currently UKAS accredited. |