Monitoring
Monitoring regimens related to anticoagulant therapy differ according to the agent being used.
Unfractionated heparin:[189][190]
There is no single, definitive approach to monitoring unfractionated heparin (UFH) for the management of venous thromboembolism (VTE). A suggested approach from a consensus guideline initiated by the Anticoagulation Forum is to check activated partial thromboplastin time (aPTT) or anti-Xa level every 6 hours until two consecutive therapeutic results are obtained, following which monitoring frequency can be reduced to once daily. Anti-Xa level monitoring may be preferred to aPTT in patients with heparin resistance, prolonged baseline aPTT, or altered heparin responsiveness. A therapeutic range of 0.3 to 0.7 units/mL is suggested when anti-Xa monitoring is used.
The British Society for Haematology recommends using UFH-calibrated anti-Xa assay over an aPTT for monitoring UFH therapy (again with a therapeutic range of 0.3 to 0.7 units/mL). Baseline aPTT should be obtained before starting UFH; if the patient has an abnormal baseline aPTT (prolonged or shortened) then aPTT should not be used for monitoring.
Vitamin K antagonist:[191]
Patients treated with a vitamin K antagonist (usually warfarin) require frequent international normalised ratio (INR) monitoring, preferably at a specialised anticoagulant clinic. However, select patients may be candidates for self-monitoring using portable point-of-care units. Patients on oral anticoagulation who self-monitor or self-manage can improve the quality of their oral anticoagulation therapy.
Direct oral anticoagulants (DOACs):[15][192]
DOACs do not require laboratory monitoring with coagulation assays. An assessment of renal function prior to initiating DOAC direct oral anticoagulant therapy, and renal and liver function monitoring during therapy, should be conducted as clinically indicated.
Therapeutic levels may need monitoring in some patients (e.g., if the patient weighs <50 kg or >120 kg).
Low molecular weight heparin (LMWH):[189][190]
Routine laboratory monitoring of LMWH anti-Xa is not recommended.
The Anticoagulation Forum consensus guidance recommends that patients with VTE receiving LMWH should be monitored for signs and symptoms of bleeding and renal function change that necessitates dose adjustment. Full blood count, platelet count, and serum creatinine should be monitored periodically.
Routine therapeutic drug monitoring of fondaparinux may not be necessary in the majority of patients; anti-Xa assay calibrated for fondaparinux may be considered if fondaparinux accumulation is suspected.
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