NOAC monitoring

Although the novel oral anticoagulants (NOAC) are attractive from many view points and their predictable pharmacokinetic dose-response curve allows fixed dosing, evaluation of anticoagulant activity might be indicated in the following circumstances:

  • in those patients are the extremes of weight, i.e. <50kg and those patients weighing >100kg
  • in cases of overdose or toxicity
  • in patients with significant renal and liver dysfunction
  • when patients are prescribed concurrent drugs, known to interact with NOAC
  • to confirm oral absorption
  • to confirm clearance of the NOAC prior to an invasive procedure
  • to assess adherence to NOAC

The Kings Anticoagulation Reference centre routinely quantitatively assays the NOAC and provides interpretive advice, so that healthcare professionals are able to individualise anticoagulant therapy for their patients.

If you wish to utilise this service, please review the 'recommended times to draw NOAC samples' table below and complete the appropriate request form below (under sampling handling).

It is important that all information in the relevant form is complete.

Recommended times to draw NOAC samples, in order to be informative:

 
Scenario Timing of drawing sample
Extremes of weight Low body weight: trough activity
High body weight: peak activity
Overdose or suspected over-anticoagulation Anytime (time since last dose(s) should be recorded on request form)
Renal or liver dysfunction Trough activity
Patient on concomitant interacting drugs Trough activity
To confirm oral absorption Peak activity
To assess adherence Anytime (time since patients claimed last dose should be recorded on the request form)
Prior to surgical procedure Anytime: ideally 24 hours pre-procedure

Trough activity refers to sample being drawn, prior to next dose. Peak activity refers to sample being drawn 1-3 hours post dose for dabigatran and 2-3 hours for rivaroxaban.

Sample handling:

Rivaroxaban and Dabigatran samples (local):

Please download the following form and complete all information, and ask patient to attend the phlebotomy department at King's College Hospital. Please refer to the ideal sample time table above, and encourage patient to attend at the relevant time for the sample, so that an informative result is obtained.

pdfNOAC assay request form for local GPs

Rivaroxaban and Dabigatran samples (out of area):

Please download the following form and complete all information. Specific instructions on how the sample should be handled and shipped are documented on this form. Please refer to the ideal sample time table above when drawing the relevant sample(s).

pdfNOAC assay request form for external samples

Send the sample and the completed form to:

Paradzai Chitongo
Blood Sciences Laboratory- Coagulation Lab
King's Thrombosis Centre
King's College Hospital
Denmark Hill
London
SE5 9RS

Reporting of results:

Results from samples received, will be sent back to the requesting professional by email.

Interpreting results:

If you wish to discuss a particular patient before deciding on whether to get the drug assayed or wish to discuss a result, please email Jig Patel at This email address is being protected from spambots. You need JavaScript enabled to view it. %20">This email address is being protected from spambots. You need JavaScript enabled to view it. in the first instance.