Effects of Dabigatran and Rivaroxaban On Routine and Specialized Coagulation Assays: A Study Using Actual Patient Plasma Samples
Bibliographic record
Abstract
Abstract Abstract 23 Background: To date, all published studies assessing the effects of the new oral anticoagulants dabigatran (dabi) and rivaroxaban (riva) on coagulation assays have used normal pooled plasma spiked with known concentrations of anticoagulant and therefore do not reflect the variability expected from patients taking these medications. Methods: We collected citrated venous blood samples from patients taking either dabi (n=43) or riva (n=10) for management of either atrial fibrillation or acute venous thrombosis. All subjects were required to have taken at least 5 doses of drug in order to reflect steady-state conditions and informed consent was obtained. The interval between last dose and phlebotomy ranged from 1 – 18 hours. Platelet-poor plasma was prepared and using the STA-R.. coagulometer (Diagnostica Stago), the following assays were performed: PT/INR using Neoplastin Plus.. (NP) and Innovin.. (IN), aPTT (Actin.. FS), thrombin time (TT), clot-based protein S (PS) activity, free PS antigen, chromogenic protein C (PC) activity, clot-based antithrombin activity, Clauss fibrinogen, dilute Russell's viper venom time (DRVVT), and factor VIII (FVIII) activity at several dilutions (1:10 to 1:160). Hemoclot.. dilute thrombin time and STA.. -Rotachrom.. anti-Xa assays were performed for quantitation of dabi and riva drug levels, respectively, using Aniara commercial plasma calibrators. Results: Median INR levels for patients on dabi were 1.1 (IN) and 1.2 (NP) and for riva were 1.15 (IN) and 1.3 (NP). The proportion of subjects with INR levels above 1.3 for dabi were 15% (IN) and 28% (NP) and for riva were 0% (IN) and 40% (NP). Median aPTT levels were 42s dabi and 32.5s riva. Although 73% of patients on dabi had an elevated aPTT (>38s), 60% of these were only mildly elevated (39–45s). Only one subject on riva had an elevated aPTT. The TT was extremely sensitive to the presence of dabi, as 100% of treated subjects had an elevated TT (>20s) and 73% were above the linearity cutoff (>100s). All subjects on riva had normal TT. As shown in Figure 1A, the clot-based PS assay was affected markedly by dabi, with patients showing artificially high PS activity with increasing drug levels, but no such effect was observed for riva (Figure 1B). For both drugs, the PS free antigen and chromogenic PC assays were unaffected. Figure 1C shows dabi also caused false elevations in antithrombin activity, though it did not affect the Clauss fibrinogen assay, which uses a much higher concentration of thrombin. Riva had no discernable effect on the antithrombin and fibrinogen assays (data not shown). Figure 1D shows that increasing levels of both anticoagulants caused artefactual decreases in FVIII activity. Increasing dilutions of patient plasma caused progressive elevation of FVIII activity, with median activity levels nearly doubling between 1:10 and 1:160 dilutions for both dabi (0.65 to 1.28) and riva (0.81 to 1.41). Finally, the DRVVT assay was prolonged (>20% elevated versus normal plasma) for 86% of dabi and 60% of riva patient plasmas. No differences were noted for any of these results between dabi 110 mg (n=14) and 150 mg (n=29) dosing. Conclusions: For the assay platforms assessed in this study, the majority of patients taking dabi and riva had near-normal INR and aPTT levels. This is discrepant with results from studies using spiked plasma samples. Clinicians should be cautioned that normal INR and aPTT results do not rule out the presence of therapeutic anticoagulant levels and the results should not be used to guide clinical decisions. Clotting-based thrombophilia testing should be avoided for patients taking these medications due to assay interferences, particularly with dabigatran. Disclosures: Teal: Bayer: Consultancy, Honoraria; Boehringer-Ingelheim: Consultancy, Honoraria. Lee:Bayer: Honoraria; Boehringer-Ingelheim: Honoraria.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.007 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".