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Faktor VIII-test

Reagent kit for determining the activity of blood coagulation factor VIII (Factor VIII Test) according to TU 9398-020-05595541-2009. Intended for determining the activity of blood coagulation factor VIII (FVIII) using a one-stage clotting method in the blood plasma of patients for the diagnosis of hemophilia A and thrombophilia, in fresh-frozen donor plasma (FFP), cryoprecipitate, and factor VIII preparations to assess their quality.

The Factor VIII Test is designed for manual use as well as on automatic and semi-automatic coagulometers capable of registering clot formation in the presence of kaolin.

Factor VIII is a glycoprotein with a molecular weight of approximately 280,000 daltons, localized in the liver, spleen, and lymphocytes, apart from plasma. In plasma, factor VIII circulates in a non-covalent complex with von Willebrand factor. Factor VIII is activated by thrombin and factor Xa and serves as a cofactor for factor IXa in the activation of factor X in the presence of phospholipids and calcium ions.

A deficiency of factor VIII causes hemophilia A, a severe inherited disorder characterized by spontaneous, often fatal bleeding, joint hemorrhages leading to early disability. Even with a reduction in the deficient factor to 30% (normal range: 50-150%), the disease manifests in a latent form and becomes evident after surgical interventions as profuse bleeding. Individuals with hemophilia A require lifelong replacement therapy with plasma-derived products.

The kit is intended for measuring the activity of factor VIII in the plasma of patients with hemophilia A, patients with an inhibitory form of hemophilia A, patients with thrombophilic conditions due to high levels of factor VIII activity, monitoring treatment results, and quality control testing of antihemophilic medicinal products (cryoprecipitate).

Principle of the method: Upon adding diluted test plasma to substrate-deficient plasma, all coagulation factors are corrected except for factor VIII. Therefore, the clotting time in the activated partial thromboplastin time (APTT) test of the mixture of diluted test and substrate-deficient plasma for factor VIII depends only on the activity of factor VIII in the test plasma. Factor VIII activity is determined based on the calibration curve of dilutions of the calibrator plasma with a known factor VIII activity.

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Kit composition:

  • Erylide, lyophilized analogue of cephalin — 1 vial;
  • Kaolin, suspension in 0.9% sodium chloride solution (5 ml/vial) — 1 vial;
  • 0.025M calcium chloride solution (5 ml/vial) — 1 vial;
  • Substrate plasma VIII, lyophilized (1 ml/vial) — 1 vial;
  • Calibrator plasma, lyophilized (1 ml/vial) — 1 vial;
  • Concentrated imidazole buffer (5 ml/vial) — 1 vial.

One kit is intended for conducting 20 analyses with a reagent consumption of 0.05 ml per analysis.

Normal and pathological values of factor VIII activity in the plasma of patients should be monitored using Control Plasma, code CP-2. High factor VIII activity in cryoprecipitate should be monitored using Pathoplasma VIII, code CP-8/9.

The Multicalibrator, code MC-16, can be used to construct a calibration graph.

Interpretation of results: Level of factor VIII activity in plasma in normal and pathological conditions.

Factor VIII activity in % Disease More than 200 Renal insufficiency Diabetes Thrombophilic conditions Hormonal contraceptive use 50 to 200 Normal 25 to 49 Hemophilia A, hidden form 5 to 24 Hemophilia A, mild form 1 to 5 Hemophilia A, moderate form Less than 1 Hemophilia A, severe form

One unit of activity is considered the activity of factor VIII contained in the pool of donor plasma taken from at least 300 healthy male donors. The activity of factor VIII is expressed in international units (IU) or in percentage, where 1 IU/ml corresponds to 100% activity.