LMWH is monitored with which assay?

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Multiple Choice

LMWH is monitored with which assay?

Monitoring LMWH relies on measuring anti-Xa activity because LMWH exerts its effect by enhancing antithrombin’s inhibition of factor Xa. The anti-Xa chromogenic assay quantifies how much Xa remains active after the LMWH–ATIII complex inhibits it; the greater the inhibition, the higher the LMWH effect, and the result correlates with dose. APTT is not a reliable measure for LMWH because its effect on clotting time is variable and not linearly related to LMWH concentration, unlike with unfractionated heparin. Platelet count is used to screen for heparin-induced thrombocytopenia, not to quantify LMWH activity. PT/INR tracks vitamin K antagonists like warfarin, not LMWH. In practice, routine LMWH monitoring isn’t needed for most patients, but if monitoring is indicated (special populations or procedures), the anti-Xa assay provides the most accurate assessment.

Monitoring LMWH relies on measuring anti-Xa activity because LMWH exerts its effect by enhancing antithrombin’s inhibition of factor Xa. The anti-Xa chromogenic assay quantifies how much Xa remains active after the LMWH–ATIII complex inhibits it; the greater the inhibition, the higher the LMWH effect, and the result correlates with dose.

APTT is not a reliable measure for LMWH because its effect on clotting time is variable and not linearly related to LMWH concentration, unlike with unfractionated heparin. Platelet count is used to screen for heparin-induced thrombocytopenia, not to quantify LMWH activity. PT/INR tracks vitamin K antagonists like warfarin, not LMWH.

In practice, routine LMWH monitoring isn’t needed for most patients, but if monitoring is indicated (special populations or procedures), the anti-Xa assay provides the most accurate assessment.

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