Abstract Number: PB0606
Meeting: ISTH 2020 Congress
Background: Classical coagulation tests are not useful for Apixaban estimation in plasma samples. Its concentration can be measured by anti Xa assays specifically calibrated, but calibrators are not widely available in clinical laboratories.
Aims: To correlate heparin calibrated (HC) anti Xa activity, measured by 2 different reagent/systems, with apixaban plasma levels, and compare their performance
Methods: Samples: 32 from patients receiving Apixaban taken at through or peak (40-525 ng/mL) and 20 from patients receiving enoxaparin (0.01-1.33 U/mL) as a control group.
Plasma apixaban concentrations measurement: HemosIL Liquid anti Xa (HEM) ACL TOP Coagulometer. Calibrator and controls: HemosIL Apixaban Calibrators and Controls (Intrumentation Laboratory, IL).
HC anti Xa activity was measured in two different laboratories by HEM assay calibrated by HemosIL Heparin calibrators in ACL TOP coagulometer (IL) and Innovance Heparin Assay (INN) in a Sysmex CS-2500 coagulometer (Siemens Health Care).
Statistic: SPSS 23 software.
Results: Correlation between Apixaban concentration and HC anti Xa activity was very good for both reagent/systems. (table 1). Deming regression demonstrated not statistically significant differences between tests in either Apixaban or heparin samples. Bland Altman analysis demonstrated low and comparable Bias for both types of samples. Pared T test also demonstrated not differences.
Expected values of HC anti Xa activity calculated by regression equations with each test at 2 apixaban concentrations one safe for some procedures and the other in the upper limit at through are shown in table 2.
Conclusions: The good correlations of HC anti Xa results with apixaban concentrations and the comparable performance of HEM and INN in Apixaban samples, demonstrate that a good and similar estimation of apixaban concentration (evaluated range) is possible with both reagent/systems. More samples, particularly at low Apixaban levels, should be tested to confirm results. These results seem to be useful in clinical laboratories to manage emergency situations.
| HC Anti Xa activity HEM vs Apixaban (ng/mL) | HC Anti Xa activity INN vs Apixaban (ng/mL) | Deming regression HC Anti Xa activity HEM vs INN | Bland Altman HC anti Xa activity HEM vs INN | |
| R2 | 0,9719 | 0,9533 | – | – |
| Linear regression Slope (95%CI) (Apixaban samples) | 0,0079 (0,0074 to 0,0083) | 0,0082 (0,0075 to 0,0089) | – | – |
| Linear regression Y intercept (95%CI) (Apixaban samples) | -0,1199 (-0,2567 to 0,0168) | -0,2666 (-0,4694 to -0,0638) | – | – |
| Bland Altman BIAS (95%CI) Apixaban Samples | – | – | – | -0,03867 (-0,5079 to 0,4306) |
| Slope (95%CI) Apixaban Samples (n=30) | – | – | 1,058 (0,8841 to 1,232) | – |
| Y intercept (95%CI) Apixaban Samples | – | – | -0,1506 (-0,4451 to 0,1439) | – |
| Slope (95%CI) LMWH samples | – | – | 0,9018 (0,7676 to 1,036) | – |
| Y intercept (95%CI) LMWH samples | – | – | 0,01039 (-0,1097 to 0,1305) | – |
| Bland Altman BIAS (95%CI) LMWH samples | – | – | – | -0.055 (-0,3415 to 0,2315) |
[Table 1 Correlation and regression lines between HC anti Xa assays and apixaban levels]
| Apixaban concentration (ng/mL) | HEM (U/mL) value (95%CI) | INN (U/mL) value (95%CI) |
| 50 | 0.27 (0.11 to 0.58) | 0.14 (0 to 0.38) |
| 200 | 1.45 (1.22 to 1.83) | 1.38 (1.03 to 1.72) |
[Table 2 HC Anti Xa activity expected by linear regression equation]
To cite this abstract in AMA style:
Martinuzzo MM, Sueldo E, López MS, Duboscq C, Viñuales ES, Mezzarobba D, Ceresetto J, Barrera LH, Arias M, Gurfinkiel M, Oyhamburu J. Apixaban Plasma Concentration Estimation by Anti Xa Activity Assay Calibrated with Heparin Calibrators with 2 Different Reagent/Systems [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/apixaban-plasma-concentration-estimation-by-anti-xa-activity-assay-calibrated-with-heparin-calibrators-with-2-different-reagent-systems/. Accessed October 1, 2023.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/apixaban-plasma-concentration-estimation-by-anti-xa-activity-assay-calibrated-with-heparin-calibrators-with-2-different-reagent-systems/