Diagnosis of haemophilia: use of an artificial factor-VIII-deficient human plasma system.
An artificial clotting system deficient in factor VIII has been made from normal human plasma. Factors XII and XI are supplied as ;activation product'. An eluate from Al(OH)(3), which has been incubated with normal plasma, supplies factors X and IX in their ;plasma' (unactivated) form with II. Factor V is provided as the supernatant after the Al(OH)(3)- treated plasma has been precipitated at one-third saturation with (NH(4))(2)SO(4). Fibrinogen is freed of factor VIII by freezing and thawing a lyophylized preparation and then added. Of these, activation product and the fibrinogen may be prepared in advance and stored frozen, and the eluate and supernatant may be made on the day of testing. A phospholipid source and CaCl(2)-solution are also required. In use, a patient's and a control plasma are first diluted in a mixture of the eluate, supernatant, and fibrinogen solution, and clotting times are recorded after completing the system by adding the phospholipid, activation product, and calcium chloride. The clotting times from the mixtures containing the patient's and the control plasmas may then be compared.