Instead, calibrated TT and anti-Xa assays
offer specific and accurate concentration monitoring under special situations.
All anti-Xa assays were performed using rivaroxaban calibrators.
Monitoring unfractionated heparin therapy: relationship between eight anti-Xa assays and a protamine titration assay.
(10) We found that hyperbilirubinemia and elevated level of free Hb in plasma samples provoked mild underestimation of heparin activity by anti-Xa assay. Colorimetric assays might be sensitive to high free Hb or high bilirubin in the specimen, and the anti-Xa assay Rotachrom is claimed to be insensitive to these substances unless bilirubin is higher than 6.6 mg/dL or Hb higher than 200 mg/dL.
Monitoring of heparin therapy by aPTT or anti-Xa assay in the ECMO setting complicated with severe hemolysis might lead to underestimation of anticoagulant heparin activity in plasma and increased risk of heparin overdose.
(18) Monitoring of heparin therapy by aPTT and anti-Xa assay in the ECMO setting complicated with severe hyperbilirubinemia could cause disproportionately prolonged aPTT relative to anti-Xa value and lead to underestimation of anticoagulant heparin activity in plasma based on anti-Xa assay.
It was observed that coadministration of the drug aprotinin to a study patient (patient 2) prolonged clotting times on each of the analyzers, although heparin concentrations remained below 0.66 kIU/L (measured by the anti-Xa assay).
The lack of agreement between absolute clotting time values and heparin concentrations determined by anti-Xa assay suggests the need for reexamination of the ECMO patient management strategy, perhaps in a multicenter pilot study using an evidence-based medicine approach.
Correlation coefficients for POCT clotting times vs plasma heparin concentration as determined via anti-Xa assay. Patient LHMT Citrated ACT ACT-LR LHMT Overall (a) 0.37 (b) 0.24 (b) 0.48 (b) 0.28 (b) (n = 195) (n = 196) (n = 200) (n = 208) 1 0.54 (c) 0.58 (d) 0.36 0.63 (d) 2 0.27 0.58 0.20 NA (e) 3 0.69 (c) 0.41 0.50 0.52 4 0.47 0.62 0.23 20.06 5 0.40 (c) 0.74 (b) 0.36 0.47 (b) 6 0.66 0.30 0.80 (c) 0.86 (b) 7 0.65 (c) 0.39 0.01 20.11 8 0.43 (d) 0.13 0.66 (c) 0.18 9 NA NA NA 0.27 10 0.31 0.66 0.87 (b) 0.76 11 0.32 0.22 0.57 (d) 0.25 12 0.25 0.58 (d) 0.62 (d) 0.76 (c) 13 0.91 (b) 0.80 (d) 0.91 (d) 0.88 (d) (a) Patient 2 excluded from overall analysis.