Resolving DOAC interference on aPTT, PT, and lupus anticoagulant testing by the use of activated carbon

Background: Direct oral anticoagulants (DOACs) affect laboratory coagulations tests. Activated carbon (AC) can be used for adsorption of DOACs during acute human intoxications.

Objectives: This study evaluates whether AC can also be used to resolve DOAC interference on in vitro clotting tests (prothrombin time [PT], activated partial thromboplastin time [aPTT], and lupus anticoagulant [LA] assays).

Patients/methods: Interference on PT, aPTT, Liquid anti-FXa, DTI, and LA screening/confirmation (SCT and dRVVT) was determined by spiking citrated plasma from 5 adult controls with 0, 20, 40, 80, 120, or 160 mg/mL AC. DOAC concentrations, PT, and aPTT were compared before and after AC addition to citrated plasma from patients receiving DOACs (n = 29), low molecular weight heparin (n = 10), and coumarin (n = 10) therapy. Samples from 69 LA screened patients were compared before and after AC addition.

Results: A concentration of 20 mg/mL AC had the lowest interference and was selected for further experiments. After AC addition, all DOAC concentrations were below the limit of quantification in the 29 treated patients, except for 2 apixaban samples. AC removed DOAC interference on PT and aPTT but had no impact on results obtained during coumarin or low molecular weight heparin therapy. Of 15 LA samples with interference resulting from DOAC therapy, 14 samples became negative and 1 positive after AC addition. Interference from coumarin therapy was not resolved. All 19 LA negative samples remained negative. AC treatment of the negative pooled plasma was required to avoid false-negative LA results in 21 known LA-positive samples.

Conclusions: AC selectively removes DOAC interference on PT, aPTT, and LA assays.