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The reagent kit for determining anti-Xa activity of heparin by coagulological method ("Reaklot-heparin") according to TU 9398-024-05595541-2011 is intended for monitoring heparin therapy by measuring the anti-Xa activity of heparin (both unfractionated and low molecular weight) in human plasma.

Method Principle: The method is based on the ability of a small amount of heparin in the tested plasma, in the presence of antithrombin III (AT III), to neutralize exogenous activated factor Xa. The process occurs in two stages:

  1. Inactivation of excess factor Xa by the AT III-heparin complex.
  2. Measurement of the coagulological activity of the residual factor Xa on a phospholipid membrane in the presence of calcium ions. Antithrombin III, fibrinogen, and factor V in the substrate plasma serve as sources of these components.

Calibration Curve: To construct the calibration curve, control plasmas with known heparin activities (provided separately, not included in the kit) as indicated in the passport are used. On the ordinate axis (Y) on a logarithmic scale, values of clotting time obtained for each control plasma are plotted. On the abscissa axis (X) on a linear scale, heparin activity is plotted in anti-Xa units per ml of plasma. Using the calibration curve and the clotting time value of the tested sample, determine the heparin activity. The calibration curve is linear in the range of heparin activity from 0 to 0.8 anti-Xa units/ml. (see coordinate grid).

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Kit composition:

  1. Lyophilized mixture of Factor Xa and phospholipids (2.0 ml) – 2 vials;
  2. Lyophilized substrate plasma (2.0 ml) – 2 vials;
  3. Calcium chloride solution 0.035 M (5.0 ml) – 1 vial.

The kit is designed for conducting 40-80 determinations.

Interpretation of results:

  • Prophylactic range – 0.1 – 0.3 anti-Xa units/ml.
  • Therapeutic range – 0.3 – 0.7 anti-Xa units/ml.