DOAC Guidance

Guidance for Laboratory Testing for Patients on DOAC

This Guidance is provided in conjunction with Trust Document. Download WHAT-HAE-002 Oral Anticoagulants –Guidelines & Procedures

The use of DOAC’s does not require any routine coagulation monitoring however in some clinical situations tests can help clinical decision making and assist patient management.

When requesting any coagulation tests for patients receiving DOAC treatment it is important to provide the clinical status, including renal & hepatic function together with time of administration of last dose. Impaired renal and hepatic function influences DOAC exposure levels due to the complexity of metabolism and elimination.

Some circumstances where measurement of anti-coagulants that do not require routine monitoring may be considered.

• Renal impairment
• Use of an interacting drug
• At the extremes of body weight (e.g. below 50 kg or above 120 kg)
• In the presence of severe, acute haemorrhage
• To assess compliance
• Following suspected overdose
• Prior to an invasive procedure with a high bleeding risk when the time from the last dose is not known
• Gastrointestinal abnormalities causing impaired absorption
• Use of non-standard doses

The anticoagulation effects of Apixaban cannot be measured using routine coagulation tests and therefore if either a PT and/or APTT assay is requested for patients on Apixaban a normal test result does not infer acceptable levels. No routine coagulation test can reliably measure the anticoagulant effect.

Please note: Point-of-Care testing (Coaguchek) is also not recommended for the measuring the anticoagulation effects of DOAC’s.

Anti-Factor Xa assay is also available for quantitation of Rivaroxaban, Apixaban & Edoxaban and a Diluted Thrombin Time is available for Dabigatran.

Clinical evidence and patient risk factors should always be considered when making clinical decisions on increased bleeding risks. Thrombophilia testing should not be performed on patients receiving DOAC treatment due to the potential influence on coagulation function.

Emergency situations / life-threatening bleeding

Please ring Ext 39617 (WRH) or 42082 (Alex)  (08:00 – 20:00) in advance of sending samples to notify the laboratory of any urgent requests. Outside of routine hours please contact Switchboard to bleep the Haematology Laboratory BMS.

First line tests

Drug	Screening test
Rivaroxaban	PT Assay
Dabigatran	APTT Assay

Quantitation

The plasma drug levels can also be quantitated, depending on the urgency of the situation. If time is critical it may not be possible to provide results for these tests due to the increased turnaround time. These requests are sent to a referral laboratory with a turnaround time of up to 4hrs.

Drug	Quantitative Assay
Rivaroxaban	Anti-Factor Xa Assay – drug specific
Apixaban	Anti-Factor Xa Assay – drug specific
Dabigatran	Direct Thrombin Inhibitor Assay
Edoxaban	Anti-Factor Xa Assay – drug specific

All laboratory results should however be interpreted with caution as the clinical significance of elevated results remains unclear.

Please contact the Coagulation Laboratory on 39617 (WRH) or 42082 (Alex) (08:00 – 20:00) or bleep the Haematology BMS on relevant site if you require any further advice.

References

Measurement of heparin, direct oral anti-coagulants and other non-coumarin anti-coagulants and their effects on haemostasis assays: A British Society for Haematology Guideline

Peter Baker, Sean Platton, Deepa J. Arachchillage, Steve Kitchen, Jignesh Patel, Renu Riat, Keith Gomez, The BSH Committee

First Published: 02 September 2024