PB1135 - Evaluation of charcoal based direct oral anticoagulant (DOAC) neutralisation in the laboratory measurement of lupus anticoagulant (LA)

Background: LA is associated with the highest thrombotic risk in antiphospholipid syndrome. LA measurement in patients on DOACs poses difficulties due to potential interference causing false positive/negatives.

Aims: Evaluate 3 charcoal-based DOAC neutralising agents for use in LA measurement in plasma samples by dilute Russell’s Viper venom time (DRVVT).

Methods: DRVVTs were performed on both charcoal treated and untreated plasmas. DRVVT was determined on non-anticoagulated plasma with LA1 and LA2 (Siemens) (CS5100 analyser Sysmex). DOAC-STOP (Haematex), DOAC-REMOVE (5-Diagnostics) and DP-Filter (5-Diagnostics) were evaluated to assess whether neutralising agents had any impact on the DRVVT in non-anticoagulated plasmas. LA positive >1.40, weak-pos 1.26-1.39 and negative < 1.25 plasmas were used. BIOPHEN Heparin LRT (HYPHEN) was used to demonstrate DOAC neutralisation.

Results: The plasma from patients on DOACs (Edoxaban (n=8), Rivaroxaban (n=11) and Apixaban (n=12), range 35-498 ng/ml) were all neutralised below the level of quantification ( < 30ng/ml) by the 3 neutralising agents.

The plasma from non-anticoagulated patients showed no change in laboratory interpretation post DOAC neutralising of for the 3 agents within the positive cohort DRVVT >1.40 and negative cohort of < 1.25. The weak positive DRVVT cohort had 8/21 DOAC-STOP, 1/9 DOAC-REMOVE and 2/8 DP-Filter shift from positive to negative. The changes in laboratory interpretation were within the pre neutralisation DRVVT range of 1.26-1.37.

Conclusion(s): The neutralisation of DOACs is effective using all 3 charcoal-based methods. The laboratory interpretation within the weak positive range must be considered with a 2nd LA method and specific antibody positivity, clinical context/history and >12 week repeat. Therefore, we demonstrated that the effect of these agents would not significantly impact on clinical diagnosis.
All 3 agents are suitable for DOAC neutralisation for DRVVT testing. We prefer DOAC-STOP due to ease of use and plasma volume flexibility.
This study highlighted the need to screen for anticoagulation as clinical details were unreliable.